New House sagging floors 1

[tonydutt]

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

 

[paddingtongreen]

A sketch would help, from your description, it sounds as though the bottom of your girders is level but the top is not.

Have any of the piers sunk?

Michael.
Timing has a lot to do with the outcome of a rain dance.

 

[rowingengineer]

You need to get a structural engineer on board or equivalent. They will take a look at the deflections under load, will be able to tell you if the joists are undersized ect. They will then find the problem which means then you can make sure the solution fits the problem, at the moment I think you’re guessing. The cracking of your tiles could be due to the flooring supporting them, the grout, the pier deflecting, the tiles being poor quality (I could list 100 of things here).

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

 

[msquared48]

You might try to do a level net on the first floor if you can get your hands on a good laser level. It could point to the problem area.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[FFENGINEER]

How are the girders holding up? a 6x6 girder supporting joists sounds fishy. any pictures?

 

[Stillerz]

I agree...using 6x6 treated posts as girders is quite bizarre.
I'd be interested in seeing a sketch as well.

Are the block piers on the interior only?

 

[trainguy]

Tony,

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

 

[tonydutt]

Thanks all for the replies so far. I haver attached some pictures as requested.
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://files.engineering.com/getfil...7c6e-4f26-bbd8-4260579066d5&file=P1050377.jpg

 

[cvg]

how about a few dimensions? spacing of the 2x12's, spacing of the 6x6's spacing of the posts

I don't see any lateral support for the joists - are the 2x12's connected to anything at the ends?

 

[rb1957]

how are the two segments of the girder conected ? do they need to be ?? (i'd think so, but not my bally-wick)

 

[dhengr]

Tony:
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.

 

[tonydutt]

Thanks for the generous responses:

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

 

[trainguy]

dhengr,

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

 

[tonydutt]

I have scanned in my house plans with the generic single cross sectional view of the house construction.

Tony

 

[southard2]

Still don't know what the span length of your 6x6 girders are. But from the cross section you posted it appears you have two stories bearing on that little 6x6 girders. for those to work the span would have to be very very short. I would get under those beams if they are 12 feet long.

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

 

[hokie66]

Tony,
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.

 

[msquared48]

I agree with Hokie here, that cross grain shrinkage could also be a problem contributing to the settlement and deflections seen. That is why I previously encouraged you to do a level not on the first floor. It WILL tell you where to look.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[SWComposites]

1) yes - what is the span of the 6x6 girders between piers?

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.

 

[csd72]

Get a structural engineer - I would hate for you to spend 12k and not fix the problem.

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.

 

[tonydutt]

Thanks for all the great tips...

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