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· Registered
76 Posts
Discussion Starter · #1 ·
What should the clearence be between framing and duct work?

I'm in Ontario Canada.

I have not been too worried about clearence other then not being close enough to cause noise issues.

The main square duct is hung pretty close to the floor joist, but I noticed that as it gets close to the furnace it gets further away.
It comes in horizontally into the part coming out of the top of the furnace.

This may just be the way it is and not done for a reason.

I have read that you can build walls right up against furnaces except for one side for access.
I do plan on building very close to the one side of the furnace and it is the cold side so I should be fine.

I got googling and found this:

Which confused me. What is the plenum? The part coming straight out the top of the furnace? It then makes a right turn and runs across the floor joists.

· retired framer
72,336 Posts
Furnace manual says 0" clearence but recommends 24" in front and 18" to the side for easy access.

So that answers that question.

Now how much clearance do I need for ducts?
You just need clearance for them to move around with expansion and not touch anything An inch or two is what we always did. Just watch your height. You always want at least 80 inches from the floor and more the better.

You should have a fire stop against the wall, we always just snapped a line on the wall 12" down from the ceiling and measured out from the wall above he duct and snapped a line


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