Cracked foundation on new construction

I’d appreciate any advice you can give me on this.
My wife and I are building a new home, and we already have our first problem. Seems the excavator got a little too aggressive with his backfilling on one long section of wall and now we have two cracks in it. The wall is an 8″ poured concrete wall 9 foot high. It is approximately 35 foot long and the two cracks split the wall roughly into thirds. Both cracks are open approxiamtely 1/32 to 1/16 of an inch on the interior of the basement and go from top to bottom vertically. I stretched a line on top of the wall, and it is bowed in about an inch now.
The concrete contractor assures me that there is plenty of rebar in the wall and there is no danger of it letting go. We had the excavator dig out some of the backfill to relieve pressure, and the wall hasn’t moved any in the week since. The general contractor wants to wait until we have the floor poured and the deck on, then chisel out the cracks and fill them with epoxy. Other people have told us that we should have this section of wall cut out and repoured.
What do you think? We plan on staying in this house for a long time, so we want to do this right. Any advice words of wisdom would be appreciated.
Replies
Your wall is probably not going anywhere. I would not expect it to move back on it's own. Even with pressure relieved on the outside what would cause it to move back? You could have a structural engineer evaluate it and decide if it is worth the hassle of fighting to get it replaced.
Was the floor sytem in place when the excavator backfilled? If it was not the excavator made a mistake in back filling.
How long after pouring the wall were the forms stripped and the backfill installed?
What size and configuration was the rebar set?
Your framer can handle the 1" bow, unless there is something critical in the design at the max position of the bow.
If your soil for backfill is clay then there will be additional lateral forces on that wall as water is accumulated in the clay and settlement begins. It may move more.
These splits mean the basement will not be dry....that wall will leak at the vertical cracks and at the baseline as the bond to the footing will be broken. The excavator should be responsible for a minimum of an injected epoxy repair of the cracks with at least a 5 years warranty against leaks.
Caulk is not and appropriate fix...it will fail. Black foundation sealant and plastic sheathing is not a fix either!
Do you plan on "finishing the basement" in the future? Think about the ramifications of a leaking wall and your plans.
'Pay the piper" and hire a good honest structural concrete engineer/specialist and let your contractor know that you will backcharge the costs to the excavator in order to have an objective professional opinion.
This will eleminate the possiblilty that the contractors "best on-site advice" is motivated by the need to avoid a repairs to keep from loosing money on this job.
Good Luck...............Iron Helix
I would require at least a drainage mat and/or one of the glue on rubber water protectors to make sure that it stays dry.
If your soil for backfill is clay then there will be additional lateral forces on that wall as water is accumulated in the clay and settlement begins. It may move more.
I am not an civil engineer or soils specialist but just an observer. I may be proven wrong by a specialist.
Until the clay or any other soil (not near dry or dry sand) is saturated with water and close to becoming a slurry, there is very little lateral force since gravity is vertical force. There were some significant lateral forces due to backfilling (hence the damage) but these were mechanically caused and not by gravity.
Think of when you have seen the removal of a foundation where the wall has been pushed/pulled inward without disturbing the soil along the wall: The up to 6-7 foot of now exposed soil simply stands in place until (1) there is drying of the soil and small amounts of the dry soil fall inward gradually over time or (2) there is a fairly hard rain and some of the top edge starts falling in due mainly to soil erosion or saturation. It will take quite a while (barring torrential rains, drying or freezing that the now exposed lower soil would never experience) for that vertcial wall of soil to become a pile of dirt.
I have recently been watching this situation once more in Halifax- about a 9 ft high vertical section of soil. We have had fairly severe rains (probably the tail end of NE's flood rains but not near as bad) for the past 2 evenings......will be interesting to see how much soil was displaced.
Edited 5/22/2006 2:00 am ET by experienced
Just a note, one of the main scenarios where clay backfill can add huge pressure is a in a cold climate. When it freezes it expands exponentially, and if I'm not mistaken it does the same thing to a lesser extent just by absorbing water.
When it freezes it expands exponentially
Could you explain this? Water expands about 10% when frozen. Do you mean that clay expands a lot more or exponentially by a factor of 10?
and if I'm not mistaken it does the same thing to a lesser extent just by absorbing water.
Some clays are expansive when they absorb water (or shrink when they dry). Usually, this fact is known; extra steps such as sand/gravel fill will be placed along the wall so that water is not held in place to cause problems. In my area, an inch or two of extruded foam may be placed against the foundation to allow for "expansion". (We have no expansive soils here but regular clay)
One thing about clay is that it's quite impervious to water percolating down through it. Actually, some building agencies/books recommend putting 2 or so inches of clay up to the foundation over properly compacted and sloped fill to drain rainwater away from the foundation. Then install 2-3" organic soil for sod/seed.
I'll agree with the fact that undisturbed soils at the exterior of the excavation do as you have described, even with clay soils.
The backfill of a foundation with disturbed clay soils creates a different scenario as the loosen clay absorbs & traps large quantities of water and becomes plasticized and thus fluid in nature. This creates lateral forces greater than the normal 45 degree calculations of sand or gravel infill.
Check out this discussion in JLC's Best Practices book in the section on soils, foundations and backfill.
Although our poster has not filled in his profile and we do not know his soil type, I am speaking from experience with the common soil types in my local area. Clay soils do absorb water, increase in weight, become plastic, and do expand both with wet and freezing conditions. Each cycle with the seasons wedges the wall further inward....especially a block wall. It takes years before clay backfill finally finishes settling.
Locally it is common practice to backfill with on site overdig materials as gravel and sand are very expensive to buy and truck in. At the Source...gravel is $5/ton and Sand is $12.
............Iron Helix
grael and sand here run $28 to $40/yard delivered to site. I wouldn't dream of backfilling with site materials.
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Just local practice!
It's all clay and the worst kind....heavy hold on water, readily plasticized, and expansive to boot!
Could not convince the locals to change for anything!
I quit tilting at that windmill years ago!
...........Iron Helix
I just do it right and ignore local practic. I've been cused out by guys trying totake apart floors after I used adhesive to put plywood to the joists...Also I ran into a local myth that you ccan't make a dry basement so there is no reason to try.
I've build two dry beasements two feet below water table, and dryed up a third that had beeen feeding mold groewth for twenty years.As long as they are ready to pay for having it right, I'm ready to do it.
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Ditto to doing it right. Sometimes that is the toughest battle to fight. I would seriously think about finding another GC. It's his job to exercise good judgement and prevent these easily preventable problems from happening. It should never have been backfilled at least without the first floor system and/or letting it cure for 28 days for minimum maximum strength. Trucking in better material is critical even if it costs a little more. The black spray on is dampproofing, NOT water proofing!I think if you re-excavate, straighten the wall, water proof, install at least the first floor frame and properly backfill you will be alright. That is a very long and high wall to be unsupported. I would hold GC accountable and if he doesn't make adequate repairs to get back on track, fire him - even if he is your brother in law. After if you are having significant problems and your not even out of the ground yet!
"As long as they are ready to pay for having it right, I'm ready to do it."
I agree wholeheartedly, BUT most locals are Penny wise and Dollar foolish!
I wish it were different, but few build for the future, most build for the now and the cheapest. Read Benson's lament in FHB 179.
.............Iron Helix
Lots of good questions and advice IronHelix... Thanks! Here are some answers to your questions.The floor system wasn't on yet, when the excavator backfilled, nor was the basement floor poured. In fact, neither one is done yet.The basment forms were stripped off after two or three days (can't remember which one right now, but I've got it written down somewhere). And the backfilling occurred 10 days after the pour.The backfill material was a clay loam soil, 3/4 inch rock was used to cover the drain line to a depth of one foot.I will talk to the cement contracotr and find out what the rebar size and configuration was.The basement is actually waterproofed on the exterior with some kind of black latex material that was sprayed on. I'm not sure what the trade name of it is, but I could find out.I think I'm going to call an engineering firm nearby tomorrow and get them to send out a structural engineer. It might cost me a little coin, but it will be worth it to know if my wall is still structurally sound.Thanks again........dmccabe_97
DM, I'd have a discussion with the building inspector too.
I'd want the wall torn out and replaced. It's already leaning and it's been compromised. I'd ask for pilasters to be placed at the cold joints and a plastice one piece membrane to be placed over the new area and lapped onto the existing walls.
How may braces did they have before they backfilled? Were the braces properly butted into something solid....like an opposing wall, or did they just drive some 2x4 stakes into the ground behind the braces?
I'm a stickler about how I brace. Other guys do a lot less in the same amount of time. It's all about technique.
blue
it really is a 9 ft wall and only 8" thick ?... wow .. where is this ?
how high is the finish grade ?
Mike, Just what I was thinking. Here it would have to be 10", possibly with extra rebar, if the grade is high. Brudoggie
We always use poured concrete foundations, backfill and do final grade before the carpenters show up. Backfill is always a sandy gravel that will allow water to percolate through the soil. We would not use a clay based soil which is heavy and would retain water. The freeze cycle would easily break a foundation. The dozer operators know to keep a safe distance from the wall, the machines are too heavy.
A crack is a potential leaking problem, improper backfill is also a potential problem. There are waterproofing membranes that are applied to the exterior of the concrete. I'd be asking the contractor to excavate and apply a membrane. There probably isn't enough open area in the crack for an injection sealer.
Using the correct backfill material is standard procedure in my area. In other places, you may have to specify what should be a common procedure.
http://www.concretenetwork.com/concrete/waterproofing_concrete_foundations/index.html
Beat it to fit / Paint it to match
Just one guys opinion, that would be a deal breaker to me. They either repour that section of wall or my business with that GC is finished. The rebar is for reinforcement, not replacement. If they've cracked the wall all the way through, that will be a weak point for the life of the house. You have water to worry about, movement in the future to worry about . . .
"Sometimes when I consider what tremendous consequences come from little things, I am tempted to think -- there are no little things" - Bruce Barton
if they replaced that wall, the keyed joints in to what's left would not be any better than what is ther now, and still require the same waterproofing / drainage scenarioI never understood whay so many people will backfill before the floor is on to backbrace it
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That is a long wall to be unsupported during backfilling, so it at least shows one instance of poor judgement on the contractors part. Any filler he adds to the crack will fill it, but won't impart any additional strength.
I'm with Piffin, and keeping what's there probably isn't any worse than repouring.
Also, it's hard to say the wall was perfectly true before the backfill, so being one inch out doesn't necessarily mean the wall moved that much, although it might.
Without seeing it first hand it's hard for any of us to say for sure if it's worth messing with, which is why paying an engineer the $500 is probably worth it if you don't trust the contractor.
In the end you need to have a good warranty, so make sure to get everything in writing if it isn't already.
In the end you need to have a good warranty, so make sure to get everything in writing if it isn't already.
What good is the warranty? It's already broken and they are trying to say that it doesn't matter!
blue
What good is the warranty? It's already broken and they are trying to say that it doesn't matter!
At least I wouldn't let them continue to build the rest of the house without a damned good warranty. Do you suggest the contract to build the rest of the house is broken and a new contractor is found?
At least I wouldn't let them continue to build the rest of the house without a damned good warranty. Do you suggest the contract to build the rest of the house is broken and a new contractor is found?
I don't think a cracked foundation voids a contract. The GC should have the opportunity to fix the problem. It's the fix that is arguable. If the GC decides to save as much money as possible and do a patch, when a re-pour is required, then the client probably has a civil case.
All of these things should be discussed with a lawyer if the re-pour isn't done. I personally wouldn't accept a patch and a warranty without a legal opinion. In my case, legal opinions of this type are not a financial burden, so perhaps I'm more prone to getting them. In the end though, if the builder is trying to dodge a major repour, I think I'd spend the couple of hundred for a consultation with a lawyer, rather than accepting anything he wanted to do without question.
I just don't see why a builder wouldn't want to do the re-pour right now, when everything is easy to do. How much could this cost...3-4000? How much profit will he make on his house? Balance the two. Think about the goodwill vs the badwill.
This is a no brainer. Do the re-pour, split the bill with the excavator.
blue
You're right to a point. But a repoured wall, that's something you have control over. That can be detailed however one wishes. The cracks, that's random, the wall is weaker at those points, and the wall is leaning in now. Distilled down, it's a screwup, and I wouldn't accept it.
I know it stinks for whoever eats it but thats what insurance is for. You can't go out and tell people well I biffed but here's why you have to live with it. You have to say man that's my fault and fix it. "Sometimes when I consider what tremendous consequences come from little things, I am tempted to think -- there are no little things" - Bruce Barton
Repouring the wall section will leave you with two cold joints. I'm with the guy who suggested bringing in the engineer.
At a minimum, I'd ensure the drainage system works, and that the foundation is waterproofed, not just damproofed.
Andy
"Never try to teach a pig to sing. It wastes your time and annoys the pig." Robert A. Heinlein
"Get off your dead #### and on your dying feet." Mom
Have the contractor put in two pilasters at each crack.This requires digging the soil,adding a footing for each one.Bore holes and epoxy rebar into wall, form the pilasters and repour. Hydraulic cement worked into the cracks from the inside will keep water out if the cold joint between the pilaster and the wall doesn't.
The bow won't be a problem.It is possible that the bow was in the formwork, the framers will make the sill plate straight,
mike
Here are a few pics of one method of wall bracing....
RE backfilling, dozer/loader operation technique is an important item that I don't think was mentioned yet. The machine should never be driven parallel to and up close to a wall, especially a long wall. The machine should be driven up to the house at a 45 or greater degree angle to the wall.
He needs to check local building codes as to how much unbalanced fill is allowed against an 8" wall - I don't think he ever really said how high the backfill is.
At a bare minimum, if it were my house, I'd like to see some extra water proofing in the areas of the cracks on the outside of the foundation. This might include drain board down to the footer drains on the whole wall, which again I don't think was mentioned.
matt, i agree...
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He needs to check local building codes as to how much unbalanced fill is allowed against an 8" wall - I don't think he ever really said how high the backfill is.>>>
wall ht, wall thickness, wall construction and unbalanced fill are all spelled out in most codes.. what is acceptable and what requires special Engineering ( PE stamp & plan )
i asked this question a long post ago ... but never received an answerMike Smith Rhode Island : Design / Build / Repair / Restore
It is approximately 35 foot long and the two cracks split the wall roughly into thirds.
Just a curious observation!!- This is just about what is recommended for pre-designed crack control joints in a wall this long. Good design would have a vertical control joint 10' in from each corner and then one every 15' along the wall.
IMHO,without seeing the wall, it does not seem to have a serious problem. My fix would be to have the exterior excavated (after bracing from the interior) and the wall pushed back to vertical and supported until the mud sill anchoring, floor framing and subfloor are in place. This now gives the rigidity and support needed for the wall.
Next, I would have the wall water proofed with extra attention given to the cracks. Backfill with good procedures pushing soil along the foundation excavation at an angle less than 45 degrees. Finish grades properly.
This seems simple enough not to require an engineer. It is less costly than a wall tear out so the contractor will be more apt to accept this alternative. It saves time and materials.
Edited 5/22/2006 12:42 pm ET by experienced
Edited 5/22/2006 12:43 pm ET by experienced
gold star recommendation!
Welcome to the Taunton University of Knowledge FHB Campus at Breaktime. where ... Excellence is its own reward!
A 9' tall, 8" thk wall should NOT be 35' long without any additional lateral reinf.
It should have reinforced "pilasters" (like a built up column) about every 10-12' (coincidence??) along the wall. Little late now.....
Maybe you can discuss a fix like this w/ your foundation contractor.
Can they vertically score out the walls at the cracks (about 12"w x 2" deep), and lay vert rebar, and form it out to create a reinforced pilaster (6" thk, and 12" wide and 9' high) at each of the crack locations. All new rebar will habe to be drilled and epoxied to exist conc.
Also need to inject epoxy into crack on the outside.
A 9' tall, 8" thk wall should NOT be 35' long without any additional lateral reinf.
Why do you say this? I have seen thousands of 8' x 8" thick walls that are over 35' long and have had virtually no structural problems. Why would the extra foot create a big problem if there is rebar in the wall?
We are talking about houses here and not heavy commercial, institutional, etc buildings. I see over building quite a bit. For example: I used to work on and build a few Permanent Wood Foundations (PWF) (the earliest is 25 years old now) in which the required footing for a full 2 storey house with 8" (well, 7+1/4") thick, 8' high foundation walls is a 2"x10" treated footing plate over a minimum of 5" compacted, 3/4" crushed stone or similar- no 8" x 16" concrete footings needed!!
On the other hand, I see true concrete slabs-on-grade (no frost wall) for single storey homes that have thickened edges approaching 12-14" deep, 8-10" wide with multiple pieces of rebar. When did the single storey house get a lot heavier than the 2 storey house??
There are a lot of contradicting practices in the building field. I have found civil engineers who work totally outside the housing field getting involved in housing for a friend or a lawsuit specing commercial stuff .
Edited 5/22/2006 12:44 pm ET by experienced
A 9' tall, 8" thk wall should NOT be 35' long without any additional lateral reinf.
Why do you say this?
Primarily because if it is not, failure (vertical cracks, and the entire wall leaning inwards at the top) can occur when a lateral load is applied.........This is not an exercise in theory........the OP's wall already failed!
I was simply reccomending a fix. Perhaps you can suggest an alternate, and apprioate, course of action for him to consider.
If you still feel that I am wrong, please re-read the original post, and explain to me, and the OP, why his already "over engineered" wall failed.
A lateral force applied to the top of a 9' tall wall will have about 13% greater turning moment at the footing than the same force on the top of an 8' wall. The amount of force req'd to create failure will vary depending on soil type, floor joist direction, climate, hight of finish grade.....etc.
Also, 8" thk, at least around here in NJ, is bare min for a (basement) foundation wall. Many twp insp require 10-12" thk walls for 9' h and reinf pilasters for walls 35' long. The extra height, coupled w/ the 35' lenght creates a large surface on which lateral loads can have an effect.
Conversely, the "extra" cost of an "over-engineered wall" (adding two of the "reinforced pilasters" mentioned in my orig post during the initial design phase) would no doubt be far less expensive, and give a much better final result, than what the OP is currebtly dealing with.
The cost of doing it right the first time is always so much less than a fix.
If you still feel that I am wrong, please re-read the original post, and explain to me, and the OP, why his already "over engineered" wall failed.
His wall moved inward, albeit only 1", because the contractor allowed the excavator to backfill with (1) no temporary interior wall support bracing and/or (2) without the main floor built and mudsills anchored in place to support the wall.
I have done a wood foundation where the weakest side had the stairwells running up along the outside. That side had to be built up with soil (127 loads of fill; building a pad for the slab-on-grade 1+1/2 storey family room, mud room, garage and 2 upper bedrooms) and compacted by a D8 cat dozer from footing plate to the 7 foot mark. We only allowed the cat to come within 4' of the wall and then used a Bomag roller close to the wood wall with the openings and no reinforcement of the top of the foundation. We monitored the whole process from the interior with a 4' level. Nothing happened!! Proper procedure will solve a lot of problems!!
PS- Further to my last paragraph: That particular wood foundation was built in 1987. There were no problems until 1999 when an excavation contractor bought the lot next door that was a slght bit higher. Ex asked the now second owner of the house if he wanted the scrub brush cleared from the back of his house all the way back to the lake. Owner would have a full lawn in exhange for Ex having easier access to his site during construction as well as improving Ex's site drainage. "Good deal" says owner...."100% increase in lawn, easy access and view of lake- all for ZERO!!!"
Next year, early summer- get call from owner (I now live 150 miles away)- during late spring, some water was coming up along the footing plate/basement concrete floor pad. He called me since I was builder and must be the wood foundation!! He was lucky that I was going back to my old haunt the next weekend to visit old friends. Arrived on site to find the grounds looking pretty good with lawns/ornamentals but the 9-10 older mature trees that were left when the rear brush was cleared are all dead.
Ex had changed the water table level in owners lot (water table was only 1.2 feet below slab (that is the lake level 80' feet away). The new water level killed all the trees by "drowning" the roots. The homeowner did not help himslf when he replaced the tall sump pump I installed to maintain a low water level with a submersible due to the "noise". He inadvertently raised the level in the sump pit about 7-8 inches.
When all was explained to him why the water was coming in and why he had a couple cords of standing firewood now (The house had a fireplace), he felt quite embarrassed about coming close to hassling me and was p___ed off at EX, the neighbour he had to live next door to. There have been no problems since he readjusted the sump pump!
Edited 5/22/2006 5:20 pm ET by experienced
Proper procedure will solve a lot of problems!!
How true........both in on-site execution, and in the design stage.
A few months ago I saw in a concrete magazine a product that was like a fiberglass mesh with some super adhesive combined with it.
The article said how they used this mesh product on a brand new foundation wall just like the O.P. is talking about. They applied it to the cracked sections and it supposedly would hold from moving any more, it was actually structural but just looked like mesh tape on the wall. It was unbelieveable.
I just looked for the magazine couldn't find it, sorry.
I do know that is was used on a new building being built for Penn State University in Erie, PA. And I think the contractor was E.E. Austin from Erie, PA.
If you're interested in looking into this stuff maybe you could get a hold of them I know they have a website.
Lots of interesting comments and advice and for the most part, you can tell it's not their foundation that was cracked due to negligence.
In commercial they jackhammer and start again. In residential they talk you out of it.
If the excavator would have swung the wrong way and dented your car would you accept that they add a little body filler and refinish it with a spray bomb can of closely matching paint or would you send it to your favourite body shop and send them or their insurance company the bill?
Who's at fault.............who was in charge of the backfilling operation?
BTW we always chalkline along the center line of a foundation prior to backfilling operations to monitor any stress by the subsequent backfilling.
Gabe
I appreciate all the good responses I got on this question. I talked to an engineer today and he is going to come out and inspect it. Without seeing it he can't say for sure, but from the description I gave him, he thinks I'll need to add pilasters at the very least and re-waterproof the wall with membrane sheets rather than just the spray on waterproofing used originally.Now comes the really fun part. At this point the GC is laying all blame on the excavator for getting too close to the foundation during the backfill. I've no doubt the excavator shares some of the blame, but from most of your postings and what the engineer told me, the wall should definitely have been braced before backfilling!! It will be interesting to see how this plays out as to who pays for the repair--the excavator, the GC, or if they split it.I'll let you know when I find out.Thanks again for the advice. dmccabe_97
the spray on waterproofing used originally
The spray on waterproofing was most likely dampproofing which is a cut asphalt product designed only to stop moisture diffusion inward from damp soils- not even close to a waterproofing product. In acid soils after 10-15 years, you're left with a black stain!!
Edited 5/22/2006 5:40 pm ET by experienced
How long did they wait (1 day?, 1 week?, 2 weeks?) before beginning the backfill operation?
Both cracks are open approxiamtely 1/32 to 1/16 of an inch on the interior of the basement and go from top to bottom vertically. I stretched a line on top of the wall, and it is bowed in about an inch now.
This is not a serious amount of cracking. If cracks would only be this small all the time. Late Friday afternoon, I did a pre-sell inspection on a 13 year old $450,000 home and found a minor shrinkage/settling crack that was 1/8"+. The owner was a little concerned but I said the interior would tell the tale. Checked thoroughly along the finished wall inside and found no signs of leakage.
If this wall has not bowed in at the footing also and the footing key is still in place, then I feel this wall can be saved with no future problems. It has bowed only 1" over 35' or 420" with no differential displacement due to the rebar. You should see some of the stuff I have seen from poor backfilling/work techniques. Fixing this would be akin scratching an itch- no major surgery required.
The cracks do need waterproofing so might as well do the whole wall. When the main floor is built on/anchored and the basement slab is poured, the wall will be stable if all other code limitations are met such as height of back fill and unbalanced loads.
If the wall is to be saved, excavated, and repaired, it should be braced from the interior when excavated.
Edited 5/23/2006 12:28 pm ET by experienced