For a 6-inch cathedral ceiling support box kit, my best overall pick is the AllFuel HST 24-inch box kit for low- to moderate-pitch roofs, which pairs a substantial support box with a spark guard cap. The AllFuel HST 11-inch box kit suits tighter ceiling layouts, while the high-pitch AllFuel HST kit is the better match for steeper roofs. The main tradeoffs are roof pitch compatibility, box dimensions, cap style, and whether you need a complete kit or only a support component. I compare all 14 options by those fit and configuration details, along with the differences between AllFuel HST, DuraPlus, and Dura-Tech components. Read on for the full breakdown and help matching a kit to your ceiling and chimney plan.
Get hardware and tech essentials delivered free with Prime
- Fast, free delivery on millions of items
- Prime Video, Amazon Music and more included
- Member-only deals all year
Key Takeaways
- Roof pitch narrows the AllFuel choices: the listed low-pitch kits cover 1/12–6/12, while the steep-roof version covers 7/12–12/12; choosing by box size alone can leave the flashing mismatched to the roof.
- Box dimensions serve different ceiling layouts: the 11-inch, 24-inch, and 36-inch square AllFuel boxes offer different framing footprints, so the largest box is not automatically the best fit.
- Complete kits reduce component matching work: several AllFuel options bundle support box, flashing, chimney components, and cap, while the Selkirk and DuraVent support boxes are component-focused choices.
- Cap style is a real distinction: the AllFuel lineup includes spark guard and flat top cap configurations; select based on the intended setup and local requirements rather than assuming one cap suits every installation.
- Brand and system compatibility matter: DuraPlus and Dura-Tech boxes belong to different named product lines, while AllFuel HST is another system; confirm the chimney pipe and listed components are compatible before combining parts.
| inch cathedral ceiling support box kit | Certification | Material |
|---|---|---|
| AllFuel HST Cathedral Ceiling | UL103HT | — |
| DuraVent DuraPlus 6-inch Basic | — | — |
| AllFuel HST Cathedral Ceiling | UL103HT | 304 stainless steel |
| AllFuel HST Cathedral Ceiling | UL103HT | 304 stainless steel |
| Selkirk 206424 6T Support Box | — | Stainless steel |
| AllFuel HST Through The Attic | UL103HT | — |
| AllFuel HST Cathedral Ceiling | UL103HT | 304 stainless steel |
| DuraVent DuraPlus 6" Flat Ceil | UL 103HT listed | Galvanized steel |
| DuraVent DuraPlus 6 in. Dia. x | — | Galvanized steel |
| AllFuel HST Through-The-Attic | UL103HT | 304 stainless steel |
| DuraVent DuraPlus 6" Square Ce | — | Galvanized steel |
| AllFuel HST 24" Tall Square Ce | UL103HT | Heavy-duty galvanized steel with stainless steel components |
| AllFuel HST 11" Tall Square Ce | UL103HT | Galvanized steel with stainless steel components |
| DuraVent Dura-Tech 36" Square | c-UL-us listed to UL 103 and ULC S604 | — |
More Details on Our Top Picks
AllFuel HST Cathedral Ceiling Kit with Spark Guard Chimney Cap, 11-inch Square Support Box, 1/12–6/12 Pitch
This is my strongest all-around pick for a 6-inch cathedral-ceiling installation when the roof pitch falls between 1/12 and 6/12. Its 11-inch square support box gives it a more compact footprint than the 36-inch-box AllFuel HST kit, while the package still includes the adapter, flashing with storm collar, and spark-arresting cap. The system is rated for runs up to 45 feet, making it better suited to taller layouts than the Selkirk 206424, which supports up to 20 feet. The tradeoff is brand lock-in: it is intended for AllFuel HST chimney components, and the pipe lengths are not included. I would choose it for a fairly standard-pitch roof and skip it if the project needs a large support opening or a steeper-pitch flashing kit.
Pros:- Includes the support box, trim, adapter, flashing, storm collar, and spark-arresting cap.
- Supports chimney runs up to 45 feet.
- UL103HT certification and compatibility with multiple residential heating appliances.
- 11-inch square box offers a smaller footprint than the 36-inch-square AllFuel HST version.
Cons:- Chimney pipe lengths must be purchased separately.
- Compatible with AllFuel HST chimney components rather than other brands.
- Flashing range does not cover roof pitches above 6/12.
Best for: Homeowners planning a 6-inch AllFuel HST chimney through a cathedral ceiling with a 1/12–6/12 roof pitch and a long pipe run.
Not ideal for: Buyers with a 7/12-or-steeper roof pitch, those needing a large ceiling opening, or anyone already committed to another chimney brand.
- Chimney diameter:6 inches
- Pipe type:Class-A double-wall chimney pipe
- Support box size:11 inches square
- Roof flashing pitch:1/12–6/12
- Maximum supported pipe length:45 feet
- Certification:UL103HT
- Included components:Stove pipe adapter, support box with trim, roof flashing with storm collar, spark-arresting chimney cap
Our verdict“Choose this kit for a complete, compact AllFuel HST setup on a low-to-moderate-pitch cathedral roof.”
DuraVent DuraPlus 6-inch Basic Through-the-Ceiling Chimney Kit
The DuraPlus kit is the lineup’s clearest choice for buyers who want a complete through-the-ceiling package built around a triple-wall chimney system. Its ceramic-blanket insulation and fire-safe expansion design address different needs from the AllFuel HST cathedral kits, which focus on a double-wall system and specific cathedral support-box configurations. The DuraPlus package supports up to 35 feet of pipe and covers wood, oil, coal, and gas appliances, giving it useful fuel flexibility. Its flashing range runs from 0/12 to 6/12, but the product data does not identify it as a cathedral-specific support-box kit, so I would verify the exact ceiling configuration before choosing it for a vaulted installation. At 28 pounds, it is also heavier to handle than the Selkirk support-box-only option. Pipe is sold separately.
Pros:- Includes a support box, adjustable flashing, cap, and adapters.
- Triple-wall construction uses ceramic blanket insulation.
- Fire-safe design allows liner expansion during a creosote fire.
- Supports wood, oil, coal, and gas appliances.
Cons:- Chimney pipe is not included.
- The 28-pound package can be difficult to position without help.
- The supplied information does not specify a cathedral support-box size or confirm vaulted-ceiling fit.
Best for: Installers committed to DuraPlus components who need a multi-fuel through-the-ceiling kit for a roof pitch up to 6/12.
Not ideal for: Buyers specifically seeking a clearly specified cathedral-ceiling support-box kit, a steep-pitch solution, or a lightweight package to position overhead.
- Model:SD9085
- Pipe diameter:6 inches
- Maximum pipe support:35 feet
- Construction:Triple-wall with ceramic blanket insulation
- Flashing pitch range:0/12–6/12
- Gauge:24 gauge
- Product dimensions:14.5 x 18 x 11 inches
- Item weight:28 pounds
- Compatible fuels:Wood, oil, coal, and gas
Our verdict“Pick this for a DuraPlus multi-fuel system when its through-the-ceiling configuration matches the planned ceiling and roof.”
AllFuel HST Cathedral Ceiling Kit with Spark Guard Chimney Cap, 36-inch Square Support Box, 1/12–6/12 Pitch
The defining reason to select this kit is its 36-inch square support box, a much larger footprint than the 11-inch box in the other low-pitch AllFuel HST kit. That makes it the better fit when the project calls for a broad cathedral-ceiling support area, though the supplied data does not establish that every installation needs that larger opening. Like its smaller sibling, it includes a spark-arresting cap, adapter, flashing, and storm collar, and it supports up to 45 feet of pipe. The AllFuel HST 24-inch-square steep-pitch kit is a more tailored alternative when the roof is 7/12–12/12; this model is limited to 1/12–6/12. Pipe remains a separate purchase, and the system is designed for AllFuel HST components, so it is a poor match for mixed-brand plans.
Pros:- Large 36-inch square support box for installations requiring a broad ceiling opening.
- Includes adapter, trim, flashing with storm collar, and spark-arresting cap.
- Supports chimney runs up to 45 feet.
- UL103HT certified and specified for several residential heating appliances.
Cons:- Large box may not suit framing layouts with limited available space.
- Chimney pipe lengths are sold separately.
- Designed for AllFuel HST Class-A double-wall components, limiting cross-brand compatibility.
Best for: Homeowners and installers who need a large support-box footprint for a 6-inch AllFuel HST cathedral-ceiling chimney on a 1/12–6/12 roof.
Not ideal for: Buyers with limited framing space, a steep roof, or a preference for a smaller support box such as the 11-inch AllFuel HST version.
- Chimney diameter:6 inches
- Support box size:36 inches square
- Material:304 stainless steel
- Compatible pipe:AllFuel HST Class-A double-wall chimney pipe
- Roof flashing pitch:1/12–6/12
- Maximum supported pipe length:45 feet
- Certification:UL103HT
- Included cap:Chimney cap with spark arrestor
Our verdict“Choose this over the 11-inch AllFuel HST kit only when the project specifically benefits from its larger support-box footprint.”
AllFuel HST Cathedral Ceiling Kit with Flat Top Chimney Cap, 24-inch Square Support Box, 7/12–12/12 Pitch
For a steep cathedral roof, this AllFuel HST kit fills a gap the 11-inch and 36-inch AllFuel HST kits do not: its 7/12–12/12 flashing range is designed for steeper pitches. The 24-inch square support box is also a middle ground between those two box sizes, while the included flat-top cap keeps the package straightforward. It supports up to 45 feet of 6-inch chimney and carries UL103HT certification. Compared with the 36-inch-box AllFuel HST model, this kit takes a less expansive support-box approach; compared with the DuraVent DuraPlus kit, it is more clearly specified for cathedral ceilings and steep roofs. Its notable compromise is the cap style: it uses a flat-top cap rather than a spark-arresting cap. Pipe is not included, and roof support may be needed when the chimney extends more than five feet above the roof.
Pros:- Flashing is specified for steep 7/12–12/12 roof pitches.
- 24-inch square support box offers a middle size between the 11-inch and 36-inch AllFuel HST options.
- Supports chimney runs up to 45 feet.
- UL103HT certified for use with multiple residential heating appliances.
Cons:- Includes a flat-top cap rather than a spark-arresting cap.
- Chimney pipe lengths must be purchased separately.
- Additional roof support may be needed when the chimney extends more than five feet above the roof.
Best for: Owners installing a 6-inch AllFuel HST chimney through a cathedral ceiling with a roof pitch from 7/12 to 12/12.
Not ideal for: Buyers with roof pitches of 6/12 or less, those who specifically want a spark-arresting cap, or projects requiring pipe in the kit.
- Chimney diameter:6 inches
- Support box size:24 inches square
- Material:304 stainless steel
- Roof flashing pitch:7/12–12/12
- Maximum supported pipe length:45 feet
- Certification:UL103HT
- Included cap:Flat-top chimney cap
- Additional support guidance:Roof support may be required when chimney extends more than 5 feet above the roof
Our verdict“Choose this kit when a steep roof pitch rules out the lower-pitch AllFuel HST cathedral kits.”
Selkirk 206424 6T Support Box
The Selkirk 206424 is not a full cathedral-ceiling kit; it is the support-box-focused choice for buyers who already have a compatible chimney plan and need a component suited to narrow roof sections, mobile homes, or standard 16-inch-on-center joists. Its included shield, support bucket, trim, and mounting screws address the support and insulation-shielding side of the job, while the AllFuel HST kits bundle roof flashing and a chimney cap as well. The Selkirk supports up to 20 feet, well below the 45-foot capacity listed for those AllFuel kits, so it is better suited to shorter runs. The supplied data limits it to 6-inch chimney and does not state a roof-pitch range or UL certification. I would confirm system compatibility and installation requirements before choosing it for a cathedral ceiling.
Pros:- Designed to fit 16-inch-on-center joists.
- Includes a cylindrical shield, support bucket, ceiling trim, and mounting screws.
- Provides insulation shielding when installed in an unoccupied attic.
- A focused component option when flashing and cap are already handled separately.
Cons:- Supports a maximum chimney height of 20 feet, less than the 45-foot AllFuel HST kits.
- Does not include the roof flashing and chimney cap supplied with the complete AllFuel HST kits.
- The supplied product data specifies 6-inch chimney diameter but does not identify a roof-pitch range or certification.
Best for: Installers with a compatible 6-inch chimney who need a support box for 16-inch-on-center framing, a mobile home, or a narrow roof section.
Not ideal for: Buyers seeking a complete cathedral-ceiling kit with flashing and cap, needing runs over 20 feet, or lacking confirmed Selkirk-system compatibility.
- Model:206424
- Supported chimney diameter:6 inches
- Maximum supported height:20 feet
- Joist fit:16 inches on center
- Material:Stainless steel
- Dimensions:15.5 x 15.4 x 25.4 inches
- Included components:Black box, cylindrical shield, support bucket, ceiling trim, mounting screws
Our verdict“Choose the Selkirk when framing fit and a support-box-only purchase matter more than getting a complete cathedral-ceiling kit.”
AllFuel HST Through The Attic Kit with Flat Top Chimney Cap for 6″ Class-A Double Wall Chimney Pipe
I’d choose this kit when the installation passes through an attic in a single-story home and a flat-top cap suits the project. The package groups the support box, insulation shield, flashing, and cap, helping reduce parts-matching work compared with piecing together a system. Its UL103HT listing and support for up to 45 feet of pipe also give it more headroom than the DuraVent DuraPlus flat ceiling support box, which is specified for up to 35 feet. The key limitation is the roof: this kit’s stated pitch range is 7/12 to 12/12, and it is not the cathedral-ceiling option in this roundup. Pipe lengths are separate, and the system is restricted to AllFuel HST components, so I’d skip it if you need a vaulted-ceiling support box or are building around another brand.
Pros:- Bundles the support box, insulation shield, roof flashing, and flat-top cap for an attic installation.
- Supports up to 45 feet of chimney pipe.
- UL103HT certified and listed for wood, gas, coal, and oil appliances.
- 304 stainless steel construction.
Cons:- Chimney pipe lengths must be purchased separately.
- Compatible only with AllFuel HST chimney components.
- The stated roof pitch range and attic configuration limit where it fits.
Best for: Homeowners installing an AllFuel HST chimney through an attic in a single-story home with a roof pitch from 7/12 to 12/12.
Not ideal for: Buyers with a cathedral or vaulted ceiling, a roof outside the stated pitch range, or a chimney system from another brand.
- Brand:AllFuel HST
- Pipe diameter:6 inches
- Chimney material:304 stainless steel
- Certification:UL103HT
- Maximum pipe support:45 feet
- Roof pitch compatibility:7/12 to 12/12
- Ceiling support box:11 inches square
- Fuel types:Wood, gas, coal, and oil
Our verdict“Choose this kit for an AllFuel HST attic installation on a steep roof, but not for a cathedral ceiling or a different chimney brand.”
AllFuel HST Cathedral Ceiling Kit with Spark Guard Chimney Cap for 6″ Diameter 304 Stainless Steel Class-A Double Wall Chimney Pipe (24″ Square Ceiling Support Box, 1/12-6/12 Pitch Roof Flashing)
This is the clearest match in this group for a cathedral or vaulted ceiling: its 24-inch-square support box is paired with a stove-pipe adapter, trim, roof flashing, storm collar, and spark-arrestor cap. Compared with the AllFuel HST Through-The-Attic Kit with Spark Guard Chimney Cap, this version is meant for a ceiling that slopes with the roof, not an attic pass-through. The 1/12 to 6/12 flashing range makes it a fit for low- to moderate-pitch roofs, while the stated 45-foot pipe capacity accommodates a substantial run. Its tradeoffs are practical: pipe lengths are not included, and the system is limited to AllFuel HST chimney components. If your roof pitch is steeper than 6/12, the through-the-attic kit is the more relevant AllFuel option.
Pros:- Designed for cathedral and vaulted ceiling installations.
- Includes a 24-inch-square support box, trim, flashing, storm collar, adapter, and spark-arrestor cap.
- Supports up to 45 feet of chimney pipe.
- UL103HT certified for a range of residential heating appliances.
Cons:- Chimney pipe lengths are sold separately.
- Compatible only with AllFuel HST chimney pipe.
- The included flashing is specified for roof pitches from 1/12 to 6/12.
Best for: Homeowners routing a 6-inch AllFuel HST chimney through a cathedral or vaulted ceiling beneath a roof pitched from 1/12 to 6/12.
Not ideal for: Buyers with a steep roof, a flat-ceiling attic installation, or chimney pipe from a brand other than AllFuel HST.
- Pipe diameter:6 inches
- Chimney type:Class-A double wall
- Material:304 stainless steel
- Ceiling support box:24 inches square
- Roof flashing pitch range:1/12 to 6/12
- Maximum supported pipe length:45 feet
- Certification:UL103HT
- Included components:Black stove-pipe adapter, black support box with trim, roof flashing with storm collar, and spark-arrestor cap
Our verdict“Pick this kit for a vaulted-ceiling AllFuel HST installation on a low- or moderate-pitch roof, and choose an attic kit for a flat-ceiling route.”
DuraVent DuraPlus 6″ Flat Ceiling Support Box with Trim Collar
I’d shortlist this when the project calls for a flat-ceiling support box in an existing or planned DuraPlus system, rather than a full installation kit. The twist-lock connection is intended to secure compatible chimney sections, and the included trim collar gives the ceiling opening a finished edge. It supports up to 35 feet of DuraPlus pipe, less than the 45 feet specified for the AllFuel HST kits, so it suits a more limited vertical run. The main distinction is scope: unlike the AllFuel HST Through-The-Attic Kit, this product does not bundle roof flashing, an insulation shield, or a cap. Its galvanized-steel construction and DuraPlus-only fit also make it a poor match for buyers assembling a mixed-brand system. Check the listed dimensions against the opening and installation plan before ordering.
Pros:- Twist-lock connection is designed for compatible DuraPlus pipe.
- Supports up to 35 feet of vertical chimney pipe.
- Includes a trim collar that can be painted to suit the room.
- UL 103HT listed for use with wood, oil, coal, and gas appliances.
Cons:- A support box and trim collar alone do not provide the flashing, cap, and other components of a complete kit.
- Compatible only with DuraPlus chimney systems.
- The trim is unfinished and requires suitable high-heat paint for customization.
Best for: Homeowners adding or replacing a support box in a 6-inch DuraPlus flat-ceiling chimney run that does not need a bundled roof kit.
Not ideal for: Buyers seeking a complete attic or cathedral-ceiling kit, needing support for more than 35 feet of pipe, or using another chimney brand.
- Brand:DuraVent
- Model:6DP-FCS
- Pipe diameter:6 inches
- Material:Galvanized steel
- Maximum pipe length:35 feet
- Dimensions:14.25 inches L x 6 inches W
- Certification:UL 103HT listed
- Warranty:Limited lifetime
Our verdict“Choose this as a DuraPlus flat-ceiling support component, not as a complete chimney installation kit or a cathedral-ceiling solution.”
DuraVent DuraPlus 6 in. Dia. x 17 in. L Galvanized Steel Vertical Installation Kit
This DuraPlus kit stands apart by being specified for manufactured housing and wood-burning stove installations. Its 23-inch ceiling support box also functions as an attic insulation shield, combining two roles that would otherwise call for separate components. Two stove-pipe adapter types add flexibility at the connection to the stove, unlike the AllFuel HST cathedral kit, which is packaged around a vaulted-ceiling route and includes roof components. The listing gives a 17-inch length and a 6-inch diameter, but it does not provide a maximum supported chimney height or describe a full roof-to-cap component set. At 30.2 pounds, it is also a substantial item to handle during installation. I’d favor it when its housing application and DuraPlus compatibility fit the plan, not when a complete cathedral-ceiling kit is the priority.
Pros:- Specified for manufactured-housing installations.
- Ceiling support box doubles as an attic insulation shield.
- Includes two types of stove-pipe adapters.
- Provides a vertical installation package for a 6-inch DuraPlus system.
Cons:- At 30.2 pounds, it is relatively heavy to handle.
- Additional chimney pipe lengths are required for a complete run.
- The supplied product data does not state a maximum supported pipe length.
Best for: Manufactured-home owners installing a compatible 6-inch DuraPlus vertical chimney with a wood-burning stove and who value the included adapter choices.
Not ideal for: Buyers who need a complete roof-and-cap kit, a specified long-run pipe capacity, or compatibility with AllFuel HST or other chimney systems.
- Brand:DuraVent
- Model:DuraPlus
- Diameter:6 inches
- Length:17 inches
- Material:Galvanized steel
- Item weight:30.2 pounds
- Part number:6DP-KTUP
- Included components:Ceiling support box and stove-pipe adapters
Our verdict“Choose this DuraPlus kit for a manufactured-home vertical installation when its included support box and adapters match your plan.”
AllFuel HST Through-The-Attic Kit with Spark Guard Chimney Cap for 6″ Diameter 304 Stainless Steel Class-A Double Wall Chimney Pipe (24″ Square Ceiling Support Box, 7/12-12/12 Pitch Roof Flashing)
For a single-story home with an attic and a steep roof, this package offers a more complete route than the DuraVent DuraPlus flat ceiling support box: it includes the support box, insulation shield, flashing, adapter, and spark-arrestor cap. The 7/12 to 12/12 flashing range is the defining fit, since it differs from the AllFuel HST cathedral-ceiling kit’s 1/12 to 6/12 range. It is specified to support up to 45 feet of chimney pipe and carries UL103HT certification. That makes it a strong attic-kit choice, but not a cathedral-ceiling support-box choice despite the 24-inch-square box. Pipe lengths remain separate, and the system works only with AllFuel HST components. I’d select it over the flat-top-cap attic kit when a spark guard is wanted and the roof pitch matches.
Pros:- Bundles support box, insulation shield, roof flashing, adapter, and spark-arrestor cap.
- Supports up to 45 feet of chimney pipe.
- Flashing is specified for steep roofs from 7/12 to 12/12.
- UL103HT certified for use with a range of residential heating appliances.
Cons:- Chimney pipe lengths must be purchased separately.
- Compatible only with AllFuel HST chimney components.
- Designed for an attic pass-through, not a cathedral-ceiling installation.
Best for: Homeowners installing an AllFuel HST chimney through an attic in a single-story home with a roof pitch from 7/12 to 12/12 who want a spark-arrestor cap.
Not ideal for: Buyers with a cathedral ceiling, a roof pitch below 7/12, or a chimney system built from another brand’s components.
- Pipe diameter:6 inches
- Material:304 stainless steel
- Ceiling support box:24 inches square
- Roof flashing pitch:7/12 to 12/12
- Maximum pipe length supported:45 feet
- Certification:UL103HT
- Chimney type:Class-A double wall
- Included components:Black stove-pipe adapter, support box, insulation shield, roof flashing, and spark-arrestor cap
Our verdict“Choose this for a steep-roof AllFuel HST attic run where a spark-arrestor cap matters; choose the cathedral kit for a vaulted ceiling.”
DuraVent DuraPlus 6″ Square Ceiling Support Box with Trim
For a cathedral-ceiling installation already planned around DuraPlus chimney pipe, this support box is a direct-fit choice with fewer separate finishing parts to source. Its built-in starter section and matching trim help create a cleaner connection at the ceiling, while its stated support capacity of up to 35 feet of vertical chimney suits many residential layouts. Compared with the DuraVent Dura-Tech 36-inch box, this model is lighter and includes a starter section, but the Dura-Tech is specified for a taller run of up to 60 feet and has stainless steel on the inner wall. The main tradeoff is system lock-in: this box is designed for DuraPlus, not other brands’ chimney pipe. At 17.2 pounds, it also takes care to position during overhead work.
Pros:- Designed specifically for 6-inch DuraPlus chimney systems
- Supports up to 35 feet of vertical chimney pipe
- Rated for continuous flue temperatures of 1000°F
- Includes a built-in starter section and matching decorative trim
Cons:- Limited to DuraPlus chimney-system compatibility
- Its 17.2-pound weight can make ceiling positioning harder
- The stated support capacity is lower than the Dura-Tech box’s 60-foot capacity
Best for: Homeowners building a 6-inch DuraPlus chimney through a flat, vaulted, or cathedral ceiling who want the starter section and trim included.
Not ideal for: Buyers using AllFuel HST, Dura-Tech, or another chimney system, or those who need a support box specified for a taller chimney run.
- Brand:DuraVent
- Model:6DP-CS24
- Part number:6DP-E30K
- Dimensions:6 in x 24 in
- Material:Galvanized steel
- Color:Black
- Weight:17.2 pounds
- Maximum vertical chimney support:35 feet
Our verdict“Choose this box for a DuraPlus cathedral-ceiling installation when a built-in starter and matching trim matter more than compatibility with other systems.”
AllFuel HST 24″ Tall Square Ceiling Support Box for 6″ Diameter, 304 Stainless Steel, Class-A Double Wall Insulated Chimney Pipe
The standout here is its stated fit for cathedral or vaulted ceilings with pitches up to 8/12, giving it a useful pitch range for buyers whose roof is steeper than the range covered by several bundled AllFuel HST cathedral kits. The 24-inch-tall box is intended for 6-inch AllFuel HST Class-A double-wall pipe, and UL103HT certification supports use with a broad range of residential heating appliances. Unlike the 11-inch AllFuel HST support box, this taller version offers more box depth, but that does not remove the need to buy a separate stove-pipe adaptor. Compatibility is also narrow: it is specified for AllFuel HST pipe only. I’d favor it when the ceiling pitch and box height fit the plan, not as a universal replacement for another brand’s support box.
Pros:- Specified for cathedral and vaulted ceilings up to an 8/12 pitch
- 24-inch depth provides a taller support-box format than the 11-inch AllFuel HST model
- UL103HT certified for a range of residential heating appliances
- Uses galvanized steel with stainless steel components
Cons:- Compatible only with AllFuel HST Class-A double-wall chimney pipe
- Stove-pipe adaptor must be purchased separately
- Its 24-inch height may not suit installations calling for a shorter box
Best for: Homeowners using 6-inch AllFuel HST Class-A chimney pipe under a cathedral or vaulted ceiling pitched up to 8/12 who need a 24-inch-tall box.
Not ideal for: Installers using another chimney brand, buyers with a pitch above 8/12, or anyone expecting the stove-pipe adaptor to come in the box.
- Brand:AllFuel HST
- Model:HST
- Box depth:24 inches
- Pipe diameter:6 inches
- Material:Heavy-duty galvanized steel with stainless steel components
- Finish and color:Painted black
- Ceiling pitch:Cathedral or vaulted ceilings up to 8/12
- Certification:UL103HT
- Compatibility:AllFuel HST Class-A double-wall chimney pipe only
Our verdict“Pick this taller AllFuel HST box when your 6-inch system and ceiling pitch match its specifications and you can source the adaptor separately.”
AllFuel HST 11″ Tall Square Ceiling Support Box for 6″ Diameter 304 Stainless Steel Class-A Double Wall Insulated Chimney Pipe
When a deep support box is unnecessary, this 11-inch-tall AllFuel HST model offers a shorter alternative to the brand’s 24-inch box. It is specified for 6-inch Class-A double-wall chimney pipe and supports both flat and cathedral-ceiling installations, so the shorter form can suit plans where ceiling space or box depth is limited. Its UL103HT certification covers a wide range of residential heating fuels and appliances. Compared with the 24-inch AllFuel HST box, the reduced height is the practical distinction; the larger model is the better match when the installation calls for more box depth. Both share the same brand-specific compatibility restriction, and this 11-inch version still needs a separate stove-pipe adaptor. I’d skip it if you need a complete kit or pipe from another manufacturer.
Pros:- Shorter 11-inch height than the 24-inch AllFuel HST alternative
- Designed for both flat and cathedral-ceiling mounting
- UL103HT certified for use with a range of residential heating appliances
- Galvanized steel construction with stainless steel components
Cons:- Compatible only with AllFuel HST Class-A chimney pipe
- A separate stove-pipe adaptor is required
- Limited to 6-inch-diameter pipe
Best for: Homeowners with a 6-inch AllFuel HST chimney system who need a shorter support box for a flat or cathedral ceiling installation.
Not ideal for: Buyers who need a 24-inch-tall box, use another brand’s Class-A pipe, or want a stove-pipe adaptor included.
- Brand:AllFuel HST
- Height:11 inches
- Compatible pipe diameter:6 inches
- Mounting type:Ceiling mount
- Material:Galvanized steel with stainless steel components
- Finish and color:Painted black
- Certification:UL103HT
- Compatibility:AllFuel HST Class-A double-wall chimney pipe
Our verdict“Choose this compact box when your AllFuel HST installation calls for an 11-inch support enclosure rather than the taller 24-inch model.”
DuraVent Dura-Tech 36″ Square Ceiling Support Box – 6″ Diameter
This is the heavy-duty pick for a 6-inch Dura-Tech system where the planned chimney run needs support for up to 60 feet. Its 36-inch square format fits flat or cathedral roofs and short attic spaces, while factory-installed twist-lock hardware gives the matching pipe a positive connection. The 430 stainless steel inner wall and Galvalume outer wall distinguish it from the shorter DuraPlus box, which includes a starter section but is specified for up to 35 feet. The extra capacity comes with a real installation cost: this box weighs 33 pounds, and its required 2-inch fuel-free clearance needs to be maintained around the installation. It is also system-specific, so buyers should match it to Dura-Tech pipe rather than treating it as a general 6-inch support box.
Pros:- Supports up to 60 feet of chimney pipe
- Factory-installed twist-lock hardware connects with the Dura-Tech system
- Suitable for flat roofs, cathedral roofs, and short attic spaces
- Includes a 2-inch trim collar and has a 430 stainless steel inner wall
Cons:- At 33 pounds, it may need extra help or support during installation
- Requires a 2-inch fuel-free clearance
- Designed for Dura-Tech chimney systems rather than other brands
Best for: Homeowners planning a long 6-inch Dura-Tech chimney run through a flat or cathedral roof who can accommodate the 36-inch box and clearance requirements.
Not ideal for: Buyers with a DuraPlus or AllFuel HST chimney, a shorter support-box requirement, or an installation where the 33-pound box and 2-inch clearance are difficult to manage.
- Brand and model:DuraVent Dura-Tech 6DT-CS36
- Diameter:6 inches
- Shape and size:Square, 36 inches
- Inner wall:430 stainless steel
- Outer wall:0.021-inch Galvalume steel
- Maximum chimney support:60 feet
- Clearance:2 inches of fuel-free space
- Rafter compatibility:16 inches on center
- Certification:c-UL-us listed to UL 103 and ULC S604
Our verdict“Choose this Dura-Tech box for a compatible 6-inch system with a long chimney run, provided the installation can meet its clearance and handling demands.”
How We Picked
I ranked these options around the decisions that shape a cathedral-ceiling installation: whether the product is a full kit or a standalone support box, its stated roof-pitch range, box dimensions, cap configuration, and the chimney system it is designed to support. A kit with the right roof flashing and included components ranks ahead of a single box for shoppers planning a complete installation, while standalone boxes remain useful when the rest of the system is already selected.
The order also reflects how clearly each option serves a distinct job. The 24-inch low-pitch AllFuel kit leads for its balanced configuration; the 11-inch version ranks well where framing space is limited, and the steep-pitch kit earns a specific role for roofs outside the low-pitch range. DuraVent and Selkirk support components are included for buyers building around those product families, but they rank below complete kits for shoppers seeking one coordinated package. I do not treat different box sizes or product lines as interchangeable: fit, listed system compatibility, and manufacturer installation instructions take priority over a broader feature list.
| inch cathedral ceiling support box kit | Certification |
|---|---|
| AllFuel HST Cathedral Ceiling | UL103HT |
| DuraVent DuraPlus 6-inch Basic | — |
| AllFuel HST Cathedral Ceiling | UL103HT |
| AllFuel HST Cathedral Ceiling | UL103HT |
| Selkirk 206424 6T Support Box | — |
| AllFuel HST Through The Attic | UL103HT |
| AllFuel HST Cathedral Ceiling | UL103HT |
| DuraVent DuraPlus 6" Flat Ceil | UL 103HT listed |
| DuraVent DuraPlus 6 in. Dia. x | — |
| AllFuel HST Through-The-Attic | UL103HT |
| DuraVent DuraPlus 6" Square Ce | — |
| AllFuel HST 24" Tall Square Ce | UL103HT |
| AllFuel HST 11" Tall Square Ce | UL103HT |
| DuraVent Dura-Tech 36" Square | c-UL-us listed to UL 103 and ULC S604 |
Factors to Consider When Choosing 6 Inch Cathedral Ceiling Support Box Kit
Before choosing a box or kit, I would settle the roof, framing, and chimney-system questions that product names alone cannot answer. These checks help prevent a common mismatch: buying a component that appears to fit a 6-inch pipe but does not suit the roof pitch, support plan, or listed chimney system.
Match Roof Pitch to the Flashing Range
Measure or verify roof pitch before choosing a cathedral kit, especially when the product specifies a limited range. In this lineup, the low-pitch AllFuel kits cover 1/12–6/12, while the listed steep-roof kit covers 7/12–12/12. The break between those ranges means a near-boundary roof deserves careful measurement rather than a visual guess. Flashing geometry is part of weather protection, not a minor accessory that can be assumed to fit. If your roof falls outside a kit’s stated range, ask the manufacturer or installer for a compatible configuration instead of forcing the closest option.
Choose Box Dimensions Around Framing and Clearance
The 11-inch, 24-inch, and 36-inch square box options in this roundup are not simply small, medium, and large versions of the same purchase. Box size affects how the opening relates to ceiling framing, available installation space, and the finished appearance. A larger box may offer a different framing footprint, but it can require more room and more planning; a compact box can be easier to place yet may not suit every layout. Check the product’s dimensions against the framing plan and required clearances, not just the nominal 6-inch chimney diameter. Confirm the manufacturer’s instructions and applicable code requirements before cutting the ceiling opening.
Decide Between a Complete Kit and a Standalone Box
A complete kit can simplify sourcing by grouping several chimney components, but it only helps if its included configuration matches the installation. A standalone support box makes more sense when you already have a compatible chimney system and need one specific component. Avoid assuming a box, pipe, cap, and flashing from different brands will work together because they share a 6-inch diameter. Check each component’s listed compatibility and installation documentation before ordering. If you are starting from scratch, compare the included parts against the full route from appliance to termination so missing adapters or support components do not derail the plan.
Treat Cap Style as a Configuration Choice
The AllFuel kits listed here offer spark guard and flat top cap configurations, so buyers have a choice beyond box size and roof pitch. Do not select a cap based only on appearance or assume that a spark guard is required for every installation. The suitable termination can depend on the chimney system, appliance, local rules, and the manufacturer’s approved setup. Confirm whether the cap is included and whether the kit’s stated configuration matches the rest of the system. When in doubt, use the appliance and chimney manufacturers’ instructions and ask a qualified installer to resolve conflicting requirements.
Keep Chimney Brand and Product Line Compatibility Intact
This roundup includes AllFuel HST, DuraPlus, Dura-Tech, and Selkirk components, but the shared 6-inch size does not establish compatibility among them. Named chimney systems can have distinct connection details, clearances, and approved component combinations. A DuraPlus support box, for example, should be checked against the intended DuraPlus setup rather than treated as a universal support part. Confirm the exact product line, diameter, and installation instructions for every section of the chimney. If you are replacing one component in an existing system, identify the installed system before choosing a new part.
Plan for Clearance, Support, and Local Approval
A support box is part of a safety-critical chimney installation, so choosing by convenience or appearance alone is not enough. Review required clearances to combustible materials, support limits, opening dimensions, and the route through the roof and ceiling. These details can affect framing work and may be governed by the product listing and local building or fire codes. Do not trim, alter, or combine parts unless the manufacturer’s instructions explicitly allow it. If the framing or roof conditions are unusual, get guidance from a qualified installer before purchasing.
Frequently Asked Questions
Can I use any 6-inch support box with a 6-inch chimney pipe?
No. A matching diameter alone does not show that the box and pipe are compatible. The products in this roundup span AllFuel HST, DuraPlus, Dura-Tech, and Selkirk, and each system may have its own approved components and connection details. Check the exact chimney line and manufacturer instructions before mixing parts. If you are replacing a box, identify the existing chimney system first.
How do I choose between the 11-inch, 24-inch, and 36-inch square boxes?
Start with the installation drawings and your framing layout, then compare the box’s actual dimensions with the required opening and clearances. The three sizes in this lineup serve different spatial needs; the largest is not automatically safer or easier to install. A compact box may fit a constrained location, while a larger footprint may suit a different framing plan. Verify support requirements and clearances in the manufacturer’s documentation before cutting or altering framing.
What if my roof pitch is between the two AllFuel kit ranges?
The listed AllFuel ranges meet at 6/12 and 7/12, so a roof near that boundary should be measured rather than estimated. Confirm the pitch using a reliable measurement and compare it with the exact kit’s stated flashing range. Do not assume the flashing will accommodate a pitch just outside its range. If the measured roof does not fall clearly within a listed range, contact the manufacturer or a qualified installer for an approved solution.
Should I buy a complete kit or a support box by itself?
A complete kit is often the more direct route when you are planning a new installation and its included parts match your roof and chimney system. A standalone box can be a better fit when compatible pipe, flashing, and termination components are already selected or installed. Compare the kit contents with your full component list instead of assuming every required part is included. Confirm the approved system combination before ordering, particularly if you plan to combine brands or product lines.
Do I need a spark guard cap rather than a flat top cap?
That depends on the approved chimney configuration, appliance, and local requirements; the cap labels alone do not settle the question. This lineup includes AllFuel kits with both spark guard and flat top cap configurations, so verify which version is intended for your specific installation. Check the appliance and chimney instructions and any applicable local rules before choosing. If those sources conflict or leave the choice unclear, ask a qualified installer or the manufacturer.
Conclusion
For most shoppers seeking a coordinated 6-inch cathedral installation, my best overall choice is the AllFuel HST 24-inch square box kit for a 1/12–6/12 roof, with its spark guard cap configuration. For a best value in practical fit, I would look first at the 11-inch AllFuel kit when the smaller box footprint suits the framing; it is not the right pick if the layout calls for a larger box. My best premium or steep-roof pick is the AllFuel kit rated for 7/12–12/12 roofs, since its pitch range addresses a need the low-pitch kits do not. For beginners, a complete kit is generally simpler to plan around than a standalone support box, but I would still confirm every included component and system match before purchase. For specific needs, choose the 36-inch AllFuel box when its framing footprint is required, or select a DuraPlus, Dura-Tech, or Selkirk support component when your installation is built around that compatible product line. The final choice should follow roof pitch, framing dimensions, and the chimney manufacturer’s instructions—not diameter alone.
Fall Picks
fall essentials
As an affiliate, we earn on qualifying purchases.
