Mikerson Posted February 28, 2015 Report Share Posted February 28, 2015 First, thanks to all that supply this forum with great answers. I've been reading the info here for a while, but have not posted before. I have 3 CMU piers supporting a beam under my house (built 1979). The floor joists sit on the beam, which is a triple 2x12 or 2x14. The wooden shims between the pier and the beam have broken, allowing the floor to sag and cause sheet rock cracks above in this one-story house. My question is, what should I replace these wood pieces with? A couple of 4x6x1/4" steel pieces at each pier? The CMUs appear to be sound, but do I need to fill them to prevent this type of thing from happening again? There is not room for a 4" cap. Anything else you notice here? Thanks guys.[:-thumbu] Click to Enlarge 41.73 KB Click to Enlarge 54.73 KB Click to Enlarge 50.52 KB Click to Enlarge 54.16 KB Click to Enlarge 50.73 KB Click to Enlarge 68.05 KB Link to comment Share on other sites More sharing options...
Jim Katen Posted February 28, 2015 Report Share Posted February 28, 2015 Those shims never did squat. They cracked a few minutes after they were installed. They've got nothing whatsoever to do with any drywall cracks. Leave the understructure alone. Anything that you do to try to fix this will only cause problems. Patch the drywall cracks before the next time you paint. Link to comment Share on other sites More sharing options...
mjr6550 Posted March 1, 2015 Report Share Posted March 1, 2015 The block cores should have been filled with concrete. If you need to jack up the beam I would use steel for anything less than 3/4" thick. If thicker than 3/4", then wood (oak is good) can be used. Link to comment Share on other sites More sharing options...
Erby Posted March 1, 2015 Report Share Posted March 1, 2015 So 36 years ago, these shims were put in and they're just now causing problems. Don't think so? Something else is happening. Get a competent inspector to look at the whole system. Link to comment Share on other sites More sharing options...
Garry Sorrells Posted March 1, 2015 Report Share Posted March 1, 2015 I would agree original shims did nothing. Steel shims are the way to go. The fact that the beam is sitting on the edge of the block raises a flew flags as to what may be going on. The floor may have been been into the sagging process for quite a while. It's that it has just been noticed recently. Jacking it up and re-shimming is a a short answer method to resolve sagging and to level out floor, if in fact the floor has sagged or was it that the house was built with a sagging floor, not uncommon with some builders. Just jacking the beam up may create other problems/issues to deal with. I would get in a good contractor that will look at the problem as a entire house and not just a jack up a beam job (and hit the road), rather a holistic approach. With laser lines you can shoot the entire floor, beam or structure and get a good idea of what may be going on. Be aware that when you move one area you will be moving many other areas of the house and creating stresses that may not be there at present. Depending on what is going on it may require making small adjustments to the beam over a long period, so as to not cause greater damage or at least reduce the effects of a sudden change of the bean. Link to comment Share on other sites More sharing options...
Greg Booth Posted March 1, 2015 Report Share Posted March 1, 2015 ............ To fix the shimming issue - that 8" block is nominal height, the actual height is 7-1/2". So too, 4" solid blocks are 3-1/2 inch in height. Remove the top block and replace with two 4" blocks and you will have picked up a 1/2" space. Then install a pair of 4" wide hardwood shims, tapped snug to the beam. Use a good grade of construction adhesive instead of mortar to affix the new blocks, and you will pick up another 1/2" of space......Greg Link to comment Share on other sites More sharing options...
kurt Posted March 1, 2015 Report Share Posted March 1, 2015 Hold it.....single story house...drywall cracks... Put up some pictures of the drywall cracks. The greatest likelihood is what Katen said in his last paragraph. It's dangerous in here. One can put up an innocuous supposed "problem", and the next thing you know there's recommendations for contractors, HI's, and structural engineers analyzing simple stuff that's in a few dozen million houses...that's wrong...but that will never mean a damn thing outside a few cosmetic cracks. Link to comment Share on other sites More sharing options...
Eric B Posted March 1, 2015 Report Share Posted March 1, 2015 Unless there's evidence that the block columns are not on footings I wouldn't do anything. Perfection can be a difficult and costly thing to achieve when close enough can work just fine. Link to comment Share on other sites More sharing options...
Jim Baird Posted March 1, 2015 Report Share Posted March 1, 2015 Piers are supposed to be capped so that the load is spread across the top surface. If not capped by cap block, then by filling cores of top course. I think those shims were stuck in there during framing because the girders, for a number of reasons, did not contact every pier, but sort of "floated". How long till they broke is a mystery. All buildings settle over time because gravity never sleeps. Are you sure the broken shims caused the drywall cracks? I agree with Kurt and Jim that it may not be worth messing with. Link to comment Share on other sites More sharing options...
Mikerson Posted March 1, 2015 Author Report Share Posted March 1, 2015 Thanks for all the replies everyone. It's obvious these cracks were patched over (poorly, I might add) at one point in time, and recracked. I can't be sure that the broken shims are what allowed the movement that caused the crack. It's clear from some streaks on the insulation that water flowed into the crawl through the vents at one point in time. How much, I don't know. I believe water is not an issue any longer. Jim is right, gravity never sleeps, so I wanted to try to correct what might be a problem and help fix the cosmetics at the same time. Here are some pics of the cracks. The first is on a wall parallel to the beam, the second is perpendicular. The pics are sideways, sorry. Click to Enlarge 20.45 KB Click to Enlarge 18.64 KB Link to comment Share on other sites More sharing options...
kurt Posted March 1, 2015 Report Share Posted March 1, 2015 Another review of the pics tells me the shims have nothing to do with it. There looks to be inconsistent mortar bedding between the blocks supporting the beam. Big old gaps. That, by itself, would cause settlement. This kinda goes along with what Baird said about the cores not being filled. The piers themselves are very poorly installed. Maybe the footing moved, maybe something I can't know because I'm not there. But it isn't the shims. Link to comment Share on other sites More sharing options...
Mikerson Posted March 1, 2015 Author Report Share Posted March 1, 2015 Kurt, Piers do have consistent mortar. The pics make it look like there is a big gap, but it's just the lighting. Link to comment Share on other sites More sharing options...
Jim Katen Posted March 1, 2015 Report Share Posted March 1, 2015 The movement was caused by shrinkage of the girder. A 2x12 will shrink a good 1/4 to 1/2 inch as it dries over the first year of construction. If there are wide swings in humidity in the crawlspace, it'll expand and contract in cycles. This is nearly universal in houses that are constructed like the one in the original post. Homeowners don't have a clue about it and most never notice it. But when they begin to suspect a problem and start looking carefully, they find the movement and they freak out about it. This is true of a lot of aspects of a house. Anyone who's ever worked in construction knows that true flat, level, plumb, and square surfaces are the exception, not the rule. Really. Honest. It's ok. As for your drywall cracks, badly patched drywall usually cracks again. If you want to do something to address this "problem" try making proper repairs to the drywall cracks: scrape away the texture, apply fiberglass tape with hot mud (setting type compound), and finish it with all purpose compound. Give it a year. If the cracks don't return, you're done. If the cracks come back, then start looking for real problems - the first would be to make absolutely certain that the crawlspace remains dry year round. Forget about the stupid shims. Link to comment Share on other sites More sharing options...
Marc Posted March 1, 2015 Report Share Posted March 1, 2015 The construction dates back to 79' so there isn't enough info to determine the cause of the cracks but like Jim K said, it sure ain't the shims. Marc Link to comment Share on other sites More sharing options...
kurt Posted March 1, 2015 Report Share Posted March 1, 2015 If the mortars OK, I'd bet a tooth it's shrinkage. Don't make it more complicated than what it is. We're talking single story wood box. Tree farm lumber shrinks an amount most folks can't believe. In that crawlspace, it could even be expanding and contracting annually enough to cause those cracks. Durbond 90, brown bag, not Easy Sand. Mesh tape moves and lets cracks read through. Use Perfa paper tape. It'll be ok. Link to comment Share on other sites More sharing options...
mjr6550 Posted March 2, 2015 Report Share Posted March 2, 2015 As others have said, the piers may have little to do with the cracks. Lumber shrinkage is a common cause of cracks, as is deflection that occurs over time (i.e. creep). Wood does not stop sagging, especially is the crawl space is damp. Also, in my area kiln-dried wood was not commonly used in the 70's. I usually see quite a bit more sagging of floors (causing door frames to rack and drywall to crack) because of this sagging. If that is the cause, then shimming the beams is not the answer. Link to comment Share on other sites More sharing options...
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