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-   -   Replacing over-spanned and cracked joists (http://www.diychatroom.com/f19/replacing-over-spanned-cracked-joists-169067/)

baysox2 01-14-2013 08:02 AM

Replacing over-spanned and cracked joists
 
I have issues with an addition where the original contractor went with some pretty cheap 2x10 joists that are spanned about 15ft. Two have already cracked and the rest are starting to deflect.

The addition is pretty small (8x15) but I think has a lot of load with a shower, toilet and laundry spanning three of the joists (two of which did crack). Because of the small space it is not possible to replace with full length joists unless we rip out the entire bathroom and pull up the floor.

I have a contractor I trust pretty good but still have qualms about his solution. Because of the space he is going to replace the current 2x10X15's with joists that are 2x10x8 and overlap on a 2x12 support beam (not sure if that is correct terminology).

The concern I have is he intends to run the 2x12 header on two 4x4 PT in a concrete footers. Any one have qualms with the 4X4 carrying the load or any other issues?

Any help would be appreciated as I have to do this soon as we have real concerns about the whole floor collapsing.

joecaption 01-14-2013 08:28 AM

If I understand you correctly it sound's like he's trying to split up the load by running a center beam made of 2 X 12's sitting on footers.
That will work but I'd make sure the footings are 24 X 24 X 8 Deep with rebar in the middle, and use a double row of concrete blocks not a 4X4.
It all has to do with the surface area, you want to try and spread out the load.
Picture someone wearing high heals as opposted to wearing flats.
I'm wondering what really caused those joist to crack, 2 X 10's should have worked.

baysox2 01-14-2013 08:40 AM

Was afraid of that
 
Thank you for the quick response Joe. Your thought was correct, the 2x12's are supposed to provide the support for the joists. This contractor has done a lot of good work for me in the past but just something about the 4X4's carrying all that load really had the little voice going in the back of my head.

I think the originals failed because they really look bad. Frankly they almost look like something from a box store bargain bin.

So i am getting back to him to change the plan and see if he's still interested.

again thanks for the response.

gregzoll 01-14-2013 08:45 AM

Post some pictures of these joists & the span.

joecaption 01-14-2013 08:48 AM

A 4 X 4 would work and easyer to do, but the block and some shims at the top under the beam would be the right way to do it.
How many homes have you ever seen proped up on just 4 X 4's?

GBrackins 01-14-2013 09:31 AM

I agree with joe and greg (posting a few photos will help). Would not use 4x4 preservative treated wood as it is known for twisting. Could build support columns from concrete block, lally columns, schedule 40 standard pipe columns, etc.

What is the span of the 2x12 beam? beam span, tributary loading and species of wood determines the size of the beam.

joed 01-14-2013 09:51 AM

I would use a steel lally column in place of concrete block or a 4x4.

wrongdave 01-14-2013 10:45 AM

Since it sounds like your contractor prefers using wood posts, why not just ask him to bump them up to 4x6 posts to give you some peace-of-mind? Cost difference will be negligeable as will the difference in work involved.

Gary in WA 01-14-2013 07:12 PM

Pictures of the existing would help, as will the spans of the joists.

Gary
PS> Unless you are parking more than two VW's up there, the post should be fine with a base/cap for positive tie/uplift resistance; http://www2.wwpa.org/Portals/9/docs/PDF/TN9.pdf


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