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kbuchholtz · Jan 5, 2008, 07:15 PM

Hello. In front of my fireplace there is a small tiled area. This is surrounded by hardwood which runs throughout the living room. The floor on the sides of the tile has dropped slightly below the level of the tile (about 1/8" or so). The wood floor around the tiles is also a bit spongy when stepped on.

I checked it out from the basement, and after pulling out the ceiling tiles I found fire damage in the floor and joists below the fireplace. It's no longer a wood burning fireplace, but has a gas insert installed. Anyway, I fear the fire damage there (from a previous owner many, many years ago) may have weakened the joists and could eventually buckle. Is this likely? There is one joist that is pretty charred, but it appears that the sub floor is in OK shape. The surface is blackened, but I don't think it went too deep as I can see wood tone at the tongue and groove.

Is there a way to add some support to these joists to make them a bit more sturdy? Not trying to level off the floors, just want to add some stability to these areas.

I don't know how long ago the fire happened, but my neighbor says he remembers 2 owners ago talking about fire damage there. I mention this because it could be old damage and pose no dangers to us. But we just bought the house in August and I'm finding these things as we live in the house longer.

Thanks.

schwim · Jan 5, 2008, 08:16 PM

Hi there,

The most common repair method is to "sister" new joists in along side the old joists. To do this, you simply cut the same dimension joist to the same length as the old, set it on the sill plate or cap along side of the old, and fasten along the span.

Sometimes, you can't get a clear shot from one end to the other, either due to wiring runs, plumbing, etc. If this is the case, then I would go as far as possible(even notching the joist to get around an obstruction, then joining them together and fastening.

I suggest screws and glue to fasten the two, as you would be surprised what a difference glue makes when trying to stiffen up a floor using this method.

Thanks,
Json

toolguyny · Jan 6, 2008, 01:18 PM

Without seeing the situation, its always a shot of course, but if its limited to "an area" within the floor joists... if they are good either side of the burn, you can "scab" a piece on the side of the joists. I'm assuming since you say its below a fireplace that this burn is near to the outside wall of the house in the basement, you should be able to fasten the scab piece on the end to the beam perhaps as well.. I would personally want to get the scab piece beyond the burn a good 3 - 4 feet or more if able to tie back and get the most strength you can.

ballengerb1 · Jan 6, 2008, 07:37 PM

Both answers are very helpful and would remove some of the bounce. Another soultion is to sandwich the damaged joist with strips of 3/4" plywoood glues and screwed to the sides of the joist. Before screwing and gluing it helps to put a jack under the joist to flex it back to original shape or even a bit bowed the other way. When your plywood, sister or scab is attached it is prestressed. Do not remove the jack for 48-72 hours.