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dirk1843 12-30-2007 04:48 PM

Hello all, newbie with questions about bracing floor....
Hello all, I am new to this forum although I have been lurking at work for quite some time.

Here is my situation:

We purchased the house we live in about a year ago. I worked alot on it doing some remodeling, tore out the bathroom, half the kitchen, paint, etc.

My problem is that I have in my opinion to much bounce in my floors. The house is brick/frame, on a crawl space about 3 blocks high. It was originally built with 1/2 plywood subfloor with 5/8 particle board ontop of that. The joist are (if memory serves) 2x10's. The house is around 45 feet long, around 30 feet wide. The joists are only supported at the outer walls and the center trough. That leaves an unsupported span of around 15 feet which I feel is where the problem lies. To add to the problem of fixing things, we have a package (all in one) heat pump with rigid duct that runs under the house and hangs below the joists.

I feel that I need to support the joists midspan. The builders used some cross bracing nailed between joists, but for whatever reason, they have pulled away somewhat. Most every cross brace has a gap between it and the joist(s). During the descision to purchase the house I noticed some bounce in the floors, but I overlooked it for a couple of the house was empty, I figured that once furniture was added and the floors "loaded" it would get better. It might have but not enough for me. The second factor was that while our previous house was on a crawl space as well, it was built with 2 layers of tounge and groove floor boards along with 3 runs of pyramid block supports of the joists along with the outer wall where they lay. That house was like living on a slab.

While I was doing the work on the house, I tore the floor out of the utility room and replaced it with 1/2 and 3/4 plywood. This made a big difference in that room, and I felt that replacing the presswood it the other rooms with plywood and screwing it down would fix the didn't. So now I am doing what I should have done while I had so much of the floor out.....going under the house and blocking things up.

Here is my plan, please point out pros and cons of it, and please offer better ways if they are out there................

Basically, I can run a support at 90 degree angle to the joists. I can not run this the full length of the house, due to the HVAC duct. I can make runs of 7 to 10 feet at a time. I was planing to use either a 4x4 or 2 2x8 nailed together as support beams. I intend on using 2 concrete cap blocks side by side as a base, and then 2-3 regular blocks on top of them. I will sit my support beam on top of them, jack the beam up and use cedar shakes for shims driven between either the joists and beam or beam and blocks, don't know which would be better. I do not intend on doing any more jacking than nessecary to load the support beam. A couple of reasons here....even thought the floors have bounce, they are for the most part level. I also don't want to crack any drywall if I can help it, as the paint and much of the drywall is new. I also have ceramic tile in the kitchen.

Due to where the crawl space acess is, and the layout of the HVAC duct, I will have to crawl in and haul blocks almost the full length of the house the forward the full width and back down the full length again. I am thinking of removing some of the plywood flooring I put down and cutting an access between 2 joists in the front part of the house. This would let me get my material to the front of the house with out all the crawling. We have not put down any flooring as of yet in this front room. No carpet or wood, so really would not be that much to go back an fix.

Please evaluate my plan for results, as well as small things I may not be thinking of as well as what would be the best choice in size of dimensional lumber for support beams.

Thanks in advance folks.......I really would like to tackle this my self.....

Bondo 12-31-2007 09:44 AM


It sounds like a Good Solid Plan,...
That'll leave you with Solid Floors..........

For such short runs,.... I believe Either the 4X4s, or the doubled 2X8s will work Just Fine.......
Although you could get away with Less blocking with the Doubled 2X8s....

Rehabber 12-31-2007 10:26 AM

I would not put concrete blocks on the ground. You need to dig 18"x18" 12" deep footing, pour concrete and use this as your footing.

dirk1843 12-31-2007 10:34 PM

Thanks for the replies so far.

I was wondering about using concrete for a footing. By my quick figures the size rehabber suggested would be around .8 of a yard. According to the calculator on quickcrete website, 2.25 sq feet at 6" would take 2 80# bags, so 4 bags for footing at 12" thick. That would figure out to be 10 footings per front length of house and 8-10 for back. That would be 80 bags of quickcrete.......or 1.6 yards.......... I may have figured wrong.

With such short runs, would not a couple of the almost solid cap blocks, maybe even 4, not suffice?? They are 3-4 inches thick and was planing on digging down until they are roughly flush with the ground.

Once again all input is appreciated..........

On a side note, I have also considering sistering the joists or adding a 2x12 between each pair of joists notched to fit in the trough and band. Of course there would be a few where I could not run them do the HVAC duct and other obstacles.....just wondering which would be better.........most efficent use of time/materials/money/labor.

Rehabber 12-31-2007 11:43 PM

Many old houses with insufficient foundations do a lot of sinking. Yea it takes quite a while but it happens. I recently jacked up the front of a house SIX inches due to an insufficient foundation. It's a huge amount of work to do to fix this stuff, but I will always believe it best to do it right.

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