As regards a wood stove and it’s clearances, most refer to distance from a combustible wall. What would define a non-combustible wall for closer clearances.
When it comes to product related construction terms, the most important definition is the one provided by the manufacturer…
Well, my definition of a ‘non-combustible’ wall would be just that, no part of it would be capable of burning. However, the only definition that really matters in this case is the one provided by the specific manufacturer(s) of the product(s) you plan to use.
While wall ‘coverings’ are frequently non-combustible — like tile, brick, stone, metal — the underlying structure often contains wood, paper faced drywall or insulation, and other materials that could catch fire if enough heat were to be transmitted through the ‘non-combustible’ wall covering. So, you need to look at the entire wall assembly.
Generally speaking, stove and flue clearances are specific to a particular product or model. These requirements are usually found in the manufacturer’s installation manual — they don’t always make it in the fancy advertisements or brochures. The installation manual is typically what local building code officials ask to see when inspecting a wood burning stove installation. So, the best place to get accurate installation specifications is directly from the manufacturer.
Wood stove manufacturers often sell optional heat shields that can be attached to the back, sides, and/or bottom of their stoves to effectively reduce clearances. Heat shields are also available for use with single wall flue pipe — most often used for horizontal runs close to a ceiling.
Depending upon the specific venting requirements for the wood stove(s) you are considering and where/how you plan to run the flue pipe, you might also want to investigate the use of double or triple wall flue pipe or insulated flue pipe. These are often used to pass through a wall or ceiling or roof.
When building our own house about 30 years ago, we installed a Vermont Castings wood stove. The wall behind the stove is wood framed, covered with fire-code sheetrock and faced with 4 inch brick veneer, which is secured to the wall with metal brick ties that allow for a 1 inch air space between the back of the brick and the face of the fire code drywall. The brick and mortar are both non-combustible and the natural convection currents flowing in the air space behind the brick helps to dissipate heat, which helps cool the fire-rated drywall and frame wall behind it.
The stove sits on a brick hearth, which was mortared in place over concrete underlayment board, which was installed over galvanized sheet metal to keep sparks from having any chance of falling through any cracks that might develop in the brick or mortar joints or concrete board and coming in contact with the plywood subfloor underneath everything.
We purchased and installed the optional rear and bottom heat shields and extra tall legs to minimize clearances while meeting the manufacturer’s installation requirements using the wall and floor construction specified.
The flue vents straight up through the roof. It is heavy gauge, single wall pipe inside the house — to provide a little additional radiant heating. A special ceiling support box and attic shield was used at the ceiling/roof penetrations, to maintain clearances away from roof rafters and insulation, with stainless steel insulated flue pipe used from there up.
Keep in mind that the manufacturer’s installation manual for the specific product(s) you wish to use will almost always take precedence over some generic “standard”. Your building inspector will most likely ask you to provide that information – make a copy of the applicable pages and tape them to the stove before the inspection – so that he or she may refer to it in order to determine if everything was properly installed. And, since the building inspector will most likely have the final say, it is probably a good idea to check with him or her before you go too far with your plans.
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