An Uncertified woodstove is basically any appliance that does not have a tag or label from a Listed Testing Agency, such as; Warnock Hersey, UL or ULC. These rating labels list the distance from appliance to combustibles that unit has been tested for.
As an Uncertified Appliance the minimum distance from wood stove to a combustible is 48 inches (4 feet or 1200 mm). The minimum size of your floor pad size is 18 inches beyond side with the loading door and 8 inches on all other sides.
Combustible means that a material fails to meet the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non- Combustibility in Building Materials”.
Noncombustible means that a material meets the acceptance criteria of CAN/ULC-S114, “Test for Determination of Non-Combustibility in Building Materials”.
Reducing Minimum Clearances Safely
We all want our wood stove installation to take up as little floor space as possible, so the reduction of minimum clearances using special shields is common. The clearances for both certified and uncertified stoves can be reduced safely using the rules set out below. The common feature of the clearance reduction rules is the air space behind the shield material. This space sets up a convection flow of air as the stove is operating and prevents most of the stove’s heat from reaching the wall behind. The percentage indicated in the table is the amount that the minimum clearance may be reduced with the particular shield system listed. Both wall and ceiling clearances may be reduced using shields.
A variety of materials can be used for clearance-reducing shields, from simple sheet metal to more decorative shields using brick, stone slices or ceramic tiles. Shields must be permanently mounted to walls. Free-standing, folding panels should not be used as shields.
Reducing Clearances With Shielding
Shield Construction Rules
- Minimum space between shield and combustibles: 21 mm (7/8 in.).
- Minimum clearance along the bottom of shield: 25 mm (1 in.).
- Maximum clearance along the bottom of shield: 75 mm (3 in.).
- Minimum clearance along the top of shield at ceiling: 75 mm (3 in.).
- Shield extension beyond each side of appliance: 450 mm (18 in.).
- Shield extension above appliance: 500 mm (20 in.).
- Edge clearance for ceiling shields: 75 mm (3 in.).
- Adhesives used in shield construction must not ignite or lose adhesive qualities at temperatures likely to be encountered.
- Mounting hardware must allow full vertical ventilation.
- Mounting hardware must not be located closer than 200 mm (8 in.) from the vertical centre line of the appliance.
- Mounting hardware which extends from the shield surface into combustibles may be used only at the lateral extremities of the shield.
Floor pads are required for ember protection and are not designed to protect floor from heat radiation.
Radiant Heat Protection
In addition to ember protection you also have to protect floor from radiant heat. The degree of protection depends on height of appliance from floor.
Less than 3 in clearance between firebox
An appliance shall be supported off the ember pad by two courses of 90 mm (3.5in) thick hollow masonry, clay or concrete units arranged to allow air circulation through them. Standard 4 inch are also acceptable for use. The layer of hollow blocks must be as large in area as the appliances bottom to protect the floor from radiation.
When using this type of radiation protection ensure your floor has adequate support for the combined load of appliance and brick.
Clearance of 75 mm (3 in) but less than 175 mm (7 in)
There are two options available for uncertified appliances that fall within the more than 75 mm and less than 175 mm floor clearance.
Note: Masonry has to be arranged to allow passage of air through cores of brick or blocks.
An appliance shall be supported off the ember pad by a single course of 90 mm (3.5in) thick hollow masonry, clay or concrete units arranged to allow air circulation through them; or directly on the ember pad provided that two sheet metal plates; the size of the firebox bottom and spaced at least 25 mm (1 in) and 25 mm from the firebox bottom and ember pad by noncombustible spacers or attachments to the appliance legs.
(a) off the ember pad by a single course of 90 mm (3.5 in) thick hollow masonry, clay or concrete units arranged to allow air circulation through the hollow cores;
(b) directly on the ember pad, provided that single sheet metal plate, the size of the firebox bottom and at least 24 gauge in thickness, is installed between the firebox bottom and the ember pad and spaced at least 50 mm (2 in) from the firebox bottom and the ember pad by noncombustible spacers or attachments to the appliance legs.
Unless installed in a basement most people will realize that it is cheaper and more aesthetically appealing to buy a new energy efficient wood stove that has been tested and has far less clearance requirements than an uncertified wood stove. The cost of buying shielding materials for floors and walls can be invested in purchasing a far superior product that will burn less wood and give more heat.