Wett Certificates for Wood Stoves

(Wood Energy Technology Transfer)

In the past month, I have seen some unbelievable deficiencies in wood stoves. Let me tell you about a few ….

Showing a two-storey home, we found a brand new wood stove, and new broadloom in the basement.  The wood stove was elevated on a three brick hearth, the broadloom butted up to the brick, and the face of the wood stove was right at the edge of the brick. The wall behind the wood stove was brick, but the wall adjacent to it was drywall with only 2′ clearance. The pipe leading from the wood stove to the wall did not appear to be double walled pipe within the wall.

The fix

  • WETT certification requires 18″ clearance from the opening of the wood stove for non-combustible materials, meaning 18″ of broadloom needs to be removed and replaced with non combustible material such as ceramics or tile.
  • To be WETT certified, requires a minimum of 4′ clearance to any combustible material.  The pipe leading from the wood stove to the wall, can be single walled, but it must be a double walled pipe once it enters a wall ie: wood or drywall

From a safety perspective, the owners should make these changes before using their wood stove for the first time. The agent was notified of the deficiency.

In another home, the wood stove was laid on a single layer of brick but there was no mortar between the bricks. This means hot embers could get between the bricks to the plywood subfloor. There was also a single walled pipe from the stove to the wood partition wall – perfectly allowable – but there is the risk of burns should someone accidently touch the pipe.

The fix

  • To correct this, the wood stove was taken out, the bricks removed, a non combustible sheet of steel put down, and the bricks were placed back on top of the sheet of steel prior to reinstalling the wood stove.
  • For safety reasons, I suggest a double walled pipe be used from the wood stove to the wall to prevent injuries

In yet another home, I found the pipe from the wood stove to the concrete wall had a hole in it and was being used.  The owner wasn’t home, so I immediately notified the listing real estate agent.

Lastly, I came across a gas/wood stove in a garage which was resting on a concrete floor and had a minimum of 4 foot clearance from any combustible. Would this pass a WETT certification – no!  A wood stove in a garage requires a minimum height of 18″ off the garage floor.  Why?  Because of carbon monoxide gases, which hug the floor, just like dry ice hugs the floor of a stage. In addition, the wood stove needs be protected.  That doesn’t mean a wooden barrier.  It means proper steel pipes, cemented into the concrete floor, so that any car driving or backing in, will not hit the wood stove. This is the same rational as the steel posts used to protect hydrants, electrical boxes, and the large propane holding tanks that dispense gas for your barbeque

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