Found a trick to fix a drafty damper without replacing it

I had this old house in Portland where the damper in the flue would never seat right. Half the heat went up the chimney and I was sick of it. So I tried using a high temp silicone rope gasket around the edge of the damper plate. Clamped it down with a C clamp overnight and it sealed up tight. Pulled the clamp off and now it fits snug every time I close it. Cost me like 12 bucks and 20 minutes. Has anyone else done something similar with rope gasket or is there a better fix?

2 comments

2 Comments

simonbell1d ago

My buddy tried that same trick on his place up in Seattle last winter. Couple things to watch out for though. The high temp silicone rope gasket is rated for like 500 degrees usually, but your damper itself can get way hotter than that if you have a real fire going. I've seen that stuff just turn to ash after a few good burns. Better off using actual furnace cement or a heavy duty gasket material meant for stoves, not just generic silicone rope. Also make sure you don't use too much or it'll keep the damper from closing all the way and just create another gap. I'd pull that clamp off and check if it's really seated right after a few uses, that stuff can shift around when it heats up.

sagea8820h ago

I did the rope gasket thing on my fireplace insert back in 2019 and it worked great for about three months before it started crumbling. Switched to a fiberglass rope gasket from a wood stove shop for like 15 bucks and that stuff is still holding up fine after four seasons of burning. Just make sure you clean the old ash and soot off the damper edge real good before you glue it down.