New House sagging floors
New House sagging floors
(OP)
First time poster...
I am a mechanical PE, but, need some structural advice for my house...
4 year old, 2-story house with a crawl space in eastern VA. Crawl is dry, tested girders and joists for moisture, no issues.
House is supported with concrete block piers. Girders are 6x6 treated lumber (not sure exactly which type of pine) and joists are 2X12 regular untreated pine.
My issue is on the first floor tile is cracking, wood floors are wavy, and drywall on a load bearing wall has cracked. second floor has several areas (above the load bearing wall from 1st floor) where drywall is cracking.
From my inspection of the crawl (random sample of 3 areas) the joists which are above the pier are high and the joists not above a pier are low (not all). So, I put a level on the girders in between the piers (on the bottom obviously) - totally level.
So, what I think I need is to do is to support the joists somehow. I have found a bunch of solutions including jack systems - which seem easy to install given the correct footing. But, then I read some posts here which discuss metal straps and whole bunch of other ideas, including sistering joists.
I could use some thoughts and ideas on possible solutions, possible downfalls, and things to avoid so I don't get taken when I get an estimate later this week.
I want to be econmical, too. The jacking system seems to be the best, but, probably the most expensive.
All the best, Tony
I am a mechanical PE, but, need some structural advice for my house...
4 year old, 2-story house with a crawl space in eastern VA. Crawl is dry, tested girders and joists for moisture, no issues.
House is supported with concrete block piers. Girders are 6x6 treated lumber (not sure exactly which type of pine) and joists are 2X12 regular untreated pine.
My issue is on the first floor tile is cracking, wood floors are wavy, and drywall on a load bearing wall has cracked. second floor has several areas (above the load bearing wall from 1st floor) where drywall is cracking.
From my inspection of the crawl (random sample of 3 areas) the joists which are above the pier are high and the joists not above a pier are low (not all). So, I put a level on the girders in between the piers (on the bottom obviously) - totally level.
So, what I think I need is to do is to support the joists somehow. I have found a bunch of solutions including jack systems - which seem easy to install given the correct footing. But, then I read some posts here which discuss metal straps and whole bunch of other ideas, including sistering joists.
I could use some thoughts and ideas on possible solutions, possible downfalls, and things to avoid so I don't get taken when I get an estimate later this week.
I want to be econmical, too. The jacking system seems to be the best, but, probably the most expensive.
All the best, Tony






RE: New House sagging floors
Have any of the piers sunk?
Michael.
Timing has a lot to do with the outcome of a rain dance.
RE: New House sagging floors
While we may suggest a few ways to solve the problem you have suggested, I doubt that this will be the cheapest solution, or solve the real problem.
Arguing with an engineer is like wrestling with a pig in mud. After a while you realize that they like it
RE: New House sagging floors
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: New House sagging floors
RE: New House sagging floors
I'd be interested in seeing a sketch as well.
Are the block piers on the interior only?
RE: New House sagging floors
Usually, a girder or beam with a simply supported span to depth ratio greater than approx. 24 could have deflection issues.
So, if the 6 x 6 girder you refer to has an unsupported length greater than 12 ft, that could be the source of the excessive deflections.
tg
RE: New House sagging floors
The joists are actually 2X10. The girders are indeed 6X6 treated lumber. I cannot find those in the 2006 IRC book for one an two story dwellings.
http://
RE: New House sagging floors
I don't see any lateral support for the joists - are the 2x12's connected to anything at the ends?
RE: New House sagging floors
RE: New House sagging floors
Putting a level on the underside of the girder, near the center of its span, sill show essentially level because the beam slope is zero there, and the deflection is approx. max. there. This tells you nothing about the magnitude of the deflection. Stretch a line along side of and 1" below the bottom of the girder, btwn. its two extreme ends, and measure up to the bot. of the girder. This will show you relative defections all along the girder. Unless you know the two extreme ends are in a level plane, this won't say much about how level things are. Then you must relate the max. girder defection locations with cracking above. Someone should analyze the loading on this girder.
Treated 6x6's make real good sill beams or sill plates and not very good bldg. center line girders. You have 2x12 jsts. framing onto this girder, therefore large loads and long spans from the 1st fl., unless someone shot a bull sizing the fl. jsts. too. Then you have a stud brg. wall and 2nd fl. loading onto the girder too. Trainguy, try rwhai@comcast.net. Trainguy was very generous in suggesting that 10 or 12' might be a reasonable span length for this girder, not knowing the actual loading, span length or load condition. This 6x6 has probably not been graded as a bending member either.
You should jack things up to straighten the girder out. Put a whole bunch more piers and ftgs. under it, or better yet a cont. ftg. and conc. blk. wall up under it, then it can be called a straight sill beam. The last sentence is only party tongue-in-cheek. You should check the statute of limitations on significant structural and cosmetic issues with a four year old house, and have the contractor fix the bull he shot. Rowingengineer has it right, you should get a local structural engineer involved, and then maybe get some legal advice too. Unless, of course, you were the builder, then you only need the engineer.
RE: New House sagging floors
1. the joists are 2X10 (I was wrong orginally). They are 16" OC
2. There are 6X6 treated girders the whole way around the perimeter of the crawl. Those are where the joists terminate for support. Some of those 6X6's are continuously supported by concrete block wall or by piers which are built adjacent to the brick wall. I don't see any unsupported lengths of girder or joists.
3. The max deflection point of the beam was considered, as there is none to very little gap (maybe an 1/8") on the ends of the level or ability to rock the the level end to end. But, some gap indicates deflection, and I concur with the string method, but as an estimation of deflection, I looked for gaps and rocked the level to see how the beam may be sloping from the center point to each opposing end. To me there was not enough to cause the delta (1/4" up to 1/2") between joists not directly above piers and those supported by the run of the girder.
4. I was not the builder. I am much more thorough than that - plus I am an NC State Grad. With grad school at GA Tech and UF.
5. From my read of the IRC 2006, the joists don't exceed any span limits and there are a lot of piers. Although the design only called for 10 PSFDL on the first floor. Maybe 20 PSFDL would have been better. I cannot tell of the design drawings accounted for the tile the builder installed or the wood floors. 10 PSFDL seems low to me, but, I haven't run the calculations.
6. I have an estimate by a design-build company on Thursday and have started a conversation with a local civil engineering firm. I may get the Civil PEs to design me a plan then implement myself.
Any ideas on the most economical methods to repair? I think the jack system will by >$10k. I think the jack system is the best from an engineering perspective, but, not the cheapest.
I may consult a lawyer if the civil guys tell me it is not to code under IRC.
Thanks and All the best,
Tony
RE: New House sagging floors
I was just throwing out some long-standing rules of thumb that would provide a first clue for the OP. Clearly, tonydutt needs to get this looked at by a structural engineer.
In no way did I intend to suggest that the girder is "safe" or "adequate" if less than 12 ft long.
Remember, its eng-tips, not get-your-free-engineering-approvals-here.com, although, that has a nice, lucrative ring to it...:)
tg
RE: New House sagging floors
I have scanned in my house plans with the generic single cross sectional view of the house construction.
Tony
RE: New House sagging floors
I agree with everyone else. Get a structural engineer not just any civil. Get someone experienced at looking at structures.
John Southard, M.S., P.E.
http://www.pdhlibrary.com
RE: New House sagging floors
If your problems are not due to deflection, they could be caused by differential shrinkage of the members. You said you have tested for moisture, but that is now. You don't know the moisture condition when the house was built. Did you check the moisture of the 6 x 6 members both at midspan and over the piers? As there appears to be no separation between the block and the wood, moisture wicking could be occurring from the subgrade.
RE: New House sagging floors
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: New House sagging floors
2) does it bother anyone that the rim joints do not bear on the rim girders?
3)"Some of those 6X6's are continuously supported by concrete block wall or by piers which are built adjacent to the brick wall." - do you mean that in some areas there are only piers along the outside wall?
- I am only an aircraft stress guy, but in my opinion this framing looks really bad. Will be real interested to hear what the local structural PE has to say.
RE: New House sagging floors
A local strutural engineer would probably cost you less than $1000, an 8% surcharge is cheap insurance to get it right!
These forums are only useful for general queries or very specific technical ones, in the case of your problem a lot of detective work is required to find the cause of the symptoms.
RE: New House sagging floors
The 6X6 girder length/spans do not exceed 7 feet. However, the locations where I am having the most problems the girder spans are 5'-1" to 6'-0".
I am not sure how VA allowed these 6X6s to be used, but, I don't have the 2003 IRC only 2006. Judging by what you good folks are saying it is at best hoky.
The moisture content thing revisit: I went under again and looked at a bunch of the girders. They have axial cracking which would appear to me to be from moisture dry out just like a treated lumber deck supports. Those same girders have very little deflection as well. Hmmm...
Tony
RE: New House sagging floors
Shouldn't wood flooring has slope of somewhat?
Are you positive there is no settlement of the piers?
RE: New House sagging floors
and repalce it with a 4" termite block and then install double 2x10 or 2x12 girders.
RE: New House sagging floors
Don't be so resistant to good advice, that's what you asked for, and there is a bunch of it in the various posts, if you know which nuggets to pick out. A structural engineer!, not a civil engineer or designer/builder. It looks like the latter caused your problems. Most of us have trouble with the IRC, so quit reading so hard or worrying about which edition you have; span tables alone don't address your problems, and your "there are a lot of piers" should include, 'but apparently not located properly,' again not tabulated in the IRC. In your first post: "joists which are above the pier are high and the joists not above a pier are low..."; in your second post #2. "I don't see any unsupported lengths of girder or joists." In my lingo the girder is unsupported btwn. the piers and the center line girder is almost certainly under sized for its spans and loading or the piers must be placed closer together and under heavy jamb loads, etc. See my first post, as I take my tongue out of my cheek. The 6x6 is deflecting and thus your first statement. Do the string thing or get a laser level down there. 6' is a long span for that 6x6 girder with some of what I think is going on there.
Economical methods of repair, as you requested, are immaterial until you understand the real problems and what's causing them. You really do need a experienced structural engineer to look at your problems, he/she will be able to assess the important details. You're not having similar problems at the exterior walls, are you? You seem resistant to giving enough or the right kind of info. needed to further the discussion here. A sketch of the whole girder line (the problem area) would have been most helpful, along with the actual jst. spans onto the girder. What's the total length of the girder line (the house), what are each of the span lengths, c/c of piers and end walls, show simple/continuous girder conditions over each pier? We just can't see the important details from here. The photo of the conc. blk. pier is nice, that's about what they usually look like. Is the girder bearing on the gross area of the pier or is it bearing on the end cross shell? Do the string thing, does it appear that any of the piers have settled, what are the relative deflections of the girders? How do simple supports (your photo) vs. continuity over supports relate to deltas and cracking? How do these spans and max. deltas relate to jamb loads above, to cracking, etc.? There's about 500 #/ft. of DL on these 6x6 girders, which, I doubt, are graded or intended to be used as significant bending members, look for a grade stamp and/or treating label. That DL a long term loading and doesn't include concentrated DL's or LL's (another 800#/ft.).
RE: SWComps question 2), no, but it's not my house either. On the exterior, it's pretty likely that the roof, wall and fl. loads are being carried by the brk. veneer, through the rim jst. and spanning jsts., if the brk. veneer was brought up tight under them, since the 6x6 sill beam will likely have shrunk across the grain. Maybe the brick veneer was not brought up tight under the rim jst. then there might be bearing issues on the sill beam. How is the brk. veneer tied to the conc. blk.? There aren't indications of openings and/or piers in the ext. found. wall, and those would be important structural considerations. Trainguy, I meant no harm, except to point out that these kinds of rules of thumb are potentially dangerous in the hands of Tony's builder or someone who doesn't even understand the loads or causes of the problems. Read my original post again, and email me some other rules, this time on railcars
RE: New House sagging floors
The spans don't seem long enough to even develop enough deflection to crack.
The axial cracking (or splitting) can be typical of a post member, but that won't affect its strength too much. I don't buy into the moisture argument since you've said the crawl space is dry.
I would suggest that it's an issue with expansion/contraction due to temperature, not moisture.
RE: New House sagging floors
It will bring more understanding if you can expand your sketch to include at least an interior pier and pointing out the defective bearing wall. The interior joist support beam (you call girder) could be the source of problems.
RE: New House sagging floors
BA
RE: New House sagging floors
There is a lot of talk on this forum about "you need an engineer not a builder...". I can understand where it comes from as this is an Engineering Tips website.
However, you cannot discount the advice of a good builder in a situation like this. Keep in mind that very good structures were built for thousands of years and remain standing ...even well before Timoshenko was born.
I doesnt seem like your house is facing an impending collapse or that the foundations are giving way. While I cannot say this for certain, your problem simply seems like shoddy construction that could have been avoided if you had a builder that knew his ass from a hole in the ground.
I have built 50-60 house which were entirely custom and many more that were not. By "built" I mean I actually drove some nails and even laid out and cut some rafters.
I am no longer employed (or self-employed as a builder)as I am a full-time structural engineer.
Having said this, it seems like this type of experience has eluded mnay on this site, no offense.
A good builder might be able to fix your problem "to code" and be out the door with the home fixed for less than reataining a structural engineer to look at it.
Blasphemy you say!!!!!
RE: New House sagging floors
I can already think of a few specific guys on here that are going to rip my ass for that last post.
RE: New House sagging floors
While history glorify builder's accomplishment, it does not keep record of failures. That is the reason we continusly to educate ourself since ancient time. As the knowlege base grows bigger and bigger, the smart fews (builders) have gradually lost their's edges to those equipped with better tools (engineers).
Hope this makes sense. Wish you, and believe you will, do well at school.
RE: New House sagging floors
I have been out of school for years and years.
The knowledge one can gain with his hands can equal that of his mind. Don't kid yourself.
RE: New House sagging floors
RE: New House sagging floors
Just offering another view...dissenting, apparently.
RE: New House sagging floors
Recently, I have spoken to one of the structural engineering firms in the area. They probably have 40 or so engineers on staff - not sure how many have sat for the PE, but, I spoke to the owner who is a fellow PE. He told me to not hire his firm, because my isse could probably be fixed by a builder type who would do the same exact thing he would propose for $4-6k.
I had one of those builder types come out with 20 years in the foundation biz. He and I went under the house and measured everything. What we couldn't find were any girders that were not level, using a laser level.
We did find joists that we low on the spans of about 7-9 feet. He wanteed $20k (which includes his engineer's fees) to put up new piers and girders and level everything, including the old girders.
Subsequently, I ran my own little experiment with a single house jack for $30 from Lowe's. I was able to begin to level out one small area of wood floor (the worst of the whole house) by lifting one joist 1/8". I am not going to move it anymore as that was just a test. Nonetheless, it was fun doing it.
Thanks again. I travel a lot ion my job and will be gone for the next 3 weeks. I will certainly follow the thread as best I can and respond. I will try to get the full drawing scanned in before I fly out Sunday morning.
Tony
I am not ready to fork over $20k
RE: New House sagging floors
2X12's can vary in depth from joist to joist by as much a 1/4 to 1/2" according to local framers I have talked to in the past. If joist hangers were used, or the joists rest on top of the 6X6's, this will call a waviness in the floor.
If 3/4" plywood was used for the flooring, plus screws and glue, much of this could have been mitigated. But the floor disaphragm was probably nailed, maybe glued, allowing the nails to loosen with time - any squeeks?
If hangers were used, shimming the seat of the hangers to get a constant depth could help. Similarly shimming the underside of the joists over the 6X6's could help too, if possible.
Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask
RE: New House sagging floors
RE: New House sagging floors
Thanks many,
Tony
RE: New House sagging floors
Another point about the cracking tile, on a Holmes on Homes show there was an episode where the title in a kitchen was cracking and the home owner was told that the floor was sagging and that was the problem. It turned out the problem was the installation of the "Hardie Board" as the tile underlayment using only drywall screw that allowed the board to flex which in turn caused the tile to crack on the grout lines.
You might want to look at the following sites concerning post jacks.
http://www.ellisok.com/ellisok/rescon.html
http://www.tigerbrandjackpost.com/super_s.htm
My old B&C textbook (1975) doesn't list 6x6 members as either joists or girders in floor construction. One other thing noted is all the tables are based on a 40 psf live loading for residential construction. .
RE: New House sagging floors
It only takes one or two short term situations to crack the grout and cause additional later cracking. - It all goes to short term conditions and not design tables that rely on historic lumber of different sizes, grading and densities. The tables are not reliable for new growth lumber of mixed species.
Dick
RE: New House sagging floors
The poor performance of the tiles may or may not be related to the unevenness of the floors. The underlayment (and fastening of such as unclesyd pointed out), the adhesive, and the grout could all be factors.
RE: New House sagging floors
By the way, while I often suggest to DIY'ers that they need a structural engineer, I am not in the camp of those suggesting that you need one to figure this out. You seem to be doing just fine on your own, with a bit of help from your friends here. A mechanical engineer should have all the logical skills needed to investigate and decide.
RE: New House sagging floors
Small drywall cracks are perfectly normal in new construction as the building materials dry out or acclimate to the humidity in the house. Usually a one-time fix.
The tile cracking could just as well be a shoddy job.
In the 12 years or so that I was building homes, the way tile was laid changed five times or more. It seems like once a year a new material comes out and people start to think that this new way is the only way to go.
I have tiled many floors and I have never been called back for cracking tile. From my experience the most important thing to mitigating floor cracks is to be sure that all plies of the floor are fastened tightly together (sub floor, backer board and any membrane).
I, for one, always use(d) a modified thinset mortar that has a latex additive for adhesion and flexibilty to adhere the tiles and also to adhere the backer-board (whatever kind it may be) to the sub floor.
I have seen many hardwood floors that were wavy even in new construction. Hardwoods absolutely need to acclimate to the house before being installed. They will absolutely expand. If they expand and have no room to grow from being installed improperly, you'll have a wavy bumpy floor from the wood buckling ever so slightly.
Your problems may well be from poor finish work.
I would at least investigate the broken tiles by pulling a few up and looking to see how the tile and substrates were installed.