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JKL 01-03-2007 07:56 PM

Could installing a furnace to the floor joists cause the floor to slope?
I have a 1920's house in which I had a new furnace installed about a year and a half ago. The contractor installed it to the floor joists in the basement crawlspace to save space (the floor of the crawlspace is dirt and uneven so maybe not a good place to rest a furnace). So essentially the furnace is hanging from the floor joists.

About 2 months ago I noticed that the floor upstairs seemed to be sloping a little bit. I'm not sure if it's always sloped or if I just started to notice it--I'd been doing other house remodeling which caused me to be notice every little flaw in the house of course. It slopes about 1/4 inch towards the foundation wall.

My question is--could the furnace be heavy enough that it's pulling the floor down and causing it to slope? It's a fairly small furnace (the house is 600 sq ft) but I don't know how heavy they are. I'm suspicious because the floor seems to slope where the furnace is. Is this inherently a really bad way to install a furnace or am I being paranoid?

Thanks for the help!

#CARRIERMAN 01-03-2007 08:08 PM


You got kind of a loaded question there. Depending on the dimentional size of the floor joist, the amount of given load, plus the distance between the floor joist all are factors in a sloping floor. Some others are probably going to be composite of the lumber and age of the lumber that was used. If you factor all this in, the additional weight of the furnace could cause some additional load on the floor joists. But for the most part, depending on the efficency of the furnace and the manufaturer of it, you are only talking about 100-300 pound including the evaporator weight. That should be well within the ability of even a pine 2"x6". This is a good sbject to ponder but I would look into what could be the major contributor to the excess load. I dont think you will find the furnace to be much of a problem. This is not my favorite way to do things, but if you don't have the room for a furnace, the only other alternative would be a combination unit. Hope some of this helps ease your mind, it now has mine racing.

Good luck

trollmastergeneral 01-03-2007 08:12 PM

You could take blocks and put them under furnace to take the weight off the furnace. then you dont have to worry.

JKL 01-03-2007 08:18 PM

I forgot to measure the joists, but they are 2x6 probably Douglas-fir (this is Oregon), about a foot (??) apart. No moisture problems that would affect structural integrity (that I know of, ha ha). The other possiblity that crossed my mind was that the bottom 1-2 boards of nearby siding are so rotten I could pull it off with my bare hands, so maybe some moisture is getting in and rotting the mudsill and that's settling? I am considering doing an addition this summer during which most of this would be ripped out anyway. I'm just hoping the floor doesn't sink too far between now and then! I'm also wondering if I should eventually get the furnace reinstalled somehow.

#CARRIERMAN 01-03-2007 08:22 PM


If the rotting wood is in the area of the furnace that would definately explain the bigger problem. Thanks for letting us know, it allowed some closure for me. I have one of those minds that can't shut down until the solution is found. I bet you are right about the mud seal.


gregzoll 01-03-2007 09:23 PM

For the mean time, jack that side of the house up, so that you can stop the settlement. Then you will be able to replace the Sillplate when you are able to next spring. The other problem that you can run into, is that there may be other problems that you are not seeing on that wall, and the rotting can be more costlier then you realize that it will be.

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