# Monolithic Slab foundation drain tile placement



## wasdifferent (Dec 18, 2004)

Pipe,
I'm assuming that the foundation and slab are installed the way that they are described. It's also difficult for me to picture exactly how they ARE done from a textual description, particularly because the description is not very detailed.



PipeGuy said:


> ..."monolithic slab foundation"...


monolithic = one pour (Pipe, I know that you already know that.) The footing and the floor are poured at the same time. The top of the slab is at the same elevation as the top of the footings. Makes for trouble with the seal at the cold joint at the bottom of the foundation wall. Any water that comes through shows up right on the basement floor.

Having the top of the slab 4" or more above the top of the footing is much better. That way, any water that enters at the footing/wall juncture goes down into the porous material under the slab, and is picked up by the footing drains. 



> The original poster also goes on to describe an "adjacent shallow foundation" next to the "8 foot deep one".


This can spell trouble as well. Anytime that porous material is installed next to a foundation it will channel water from the surrounding cohesive soil into the foundation, unless it is picked up by a drain and removed. If there is gravel around this shallow foundation and no method is employed to get rid of the water that it soaks up, it will go through the wall and unto the basement floor. Don't count on the moisture barrier to stop this from happening. There is no room for optimism here. Even if there is a drain tile for this shallow foundation, you can still expect lots of water to run through the deep foundation unless the whole system has been set up with logic and care. It is usually better to excavate 8 foot instead of having a "shallow foundation", and eliminate the possibility of these problems. It doesn't cost much more. On a SMALL job, the actual volume of soil excavated, and volume of concrete poured doesn't change the final cost that much. The price difference is cheap insurance.



> Is a crawl space a type of foundation?


Here's the deal: If we dig down 4 feet, pour, and backfill we have a frost wall. If we don't backfill the inside, we are leaving a "crawl space" (because it is 4 feet instead of 8 feet).



> I was under the impression that a 'foundation' wall was a wall that had no adjoining occupiable space - that it was entirely below the inhabitable structure. What is it that puts the 'foundation' into a foundation wall?


I generally use the terms _foundation wall_ and _basement wall_ interchangeably. Maybe I'm wrong on this...



> ...I get info on a precast "monolithic foundation" system...


Out of left field. Off topic here. (No offense, interesting topic in itself.)

Please forgive me for being so freakin' redundant but: 
Again, in my opinion, if you take into account that WATER SEEKS IT'S OWN LEVEL, everything else falls nicely into place. Approaching the problem from any other direction is NOT going to work. Newbie contractors have a tendency to OUTSMART THEMSELVES with ideas that EXACERBATE the problem by channeling water into the basement. It's a simple case of "Keep it simple stupid". There is a standard method for dealing with these problems, all you have to do is OPEN A FREAKIN' BOOK. Most code books contain typical footing drain detail drawings, and the EOR supplies a section drawing. Somebody(s) were either lazy, cheap, or stupid on this job. 

Lastly, with all of the blah, blah, blah... that has been posted here, somewhere along the line the original poster should have said "EUREKA! WATER SEEKS IT'S OWN LEVEL!" The fact that this has not happened is indicative that he, his building inspector, and his idiotic contractor will probably be screwing around with this problem for the next several decades, trying to re-invent the wheel...
Best regards,


----------



## PipeGuy (Oct 8, 2004)

mikesewell said:


> I generally use the terms _foundation wall_ and _basement wall_ interchangeably.


THAT's really what I was wondering about - if there is a difference.


----------



## wasdifferent (Dec 18, 2004)

PipeGuy said:


> THAT's really what I was wondering about - if there is a difference.


Well, now that you mention it, a foundation doesn't necessarily mean a basement. Driven timber piles would be a foundation, but not a basement.


----------



## PipeGuy (Oct 8, 2004)

mikesewell said:


> Well, now that you mention it, a foundation doesn't necessarily mean a basement



Once again...



PipeGuy said:


> I was under the impression that a foundation *WALL* was a *WALL* that had no adjoining occupiable space - that it was entirely below the inhabitable structure. What is it that puts the 'foundation' into a foundation *WALL*?


----------



## wasdifferent (Dec 18, 2004)

Pipe,
The fact that it supports the structure, makes it a foundation. The GROUND can be considered to be a foundation. I believe that the subject of habitable space is a separate issue.

There is an online construction dictionary, I'll google it when I get time.

Am I missing your point?...


----------



## wasdifferent (Dec 18, 2004)

My _BNI Construction Dictionary Illustrated_ says that a foundation wall is the portion of a load bearing wall below grade, or below the floor joists, which transmits the load to the footings.

My _McGraw-Hill Dictionary of Engineering_ says that a foundation is the portion of the structure which transmits the load to the ground, or that the foundation is the ground itself.

http://www.infoforbuilding.com/dictionary_d-g2.html

http://www.homebuildingmanual.com/Glossary.htm

http://construction.dictionary.kamous.com/translator/reference.asp

Google key words "online construction dictionary" or "online engineering dictionary"

Help?

P.S. I've spent THOUSANDS of dollars over the years on my library of engineering and construction books. I think that my computer now makes my library worth about 2 cents. LOL.


----------



## PipeGuy (Oct 8, 2004)

Thanks Mike. I'll do the reading.


----------



## J Hague (Mar 22, 2005)

*Planning the fix*

I got a licensed PE to design a solution for remedial measures. He opted for a minimum impact on work in place, saying that with only a 4 foot depth back fill leaking we can probably improve drainage and block the horizontal joint between block and concrete, and achieve a dry space. 

Having him make a solution, meant there was a neutral party coming up with it.

He advised making changes one step at a time and testing each one ... to assure that we were getting the leak. But the contractors are not willing to do the step wise testing and then more installations. They want to do it all at once, and risk having to come back for further work.

However there is a warranty against leaks, so they'll just have to work later if this fails. 

In the upcoming dry days, the foundation will be uncovered and a keyway cut in to the slab next to wall. Either hydraulic cement and or a hard rubber water stop will be jambed into the keyway and at the joint. 

After that, a whole new application of the waterproofing membrane will be applied. This time it will cover the vertical joint between addition and old house it a hard to access area, such as it did not do before. In addition the membrane will be sprayed across the top of the concrete slab projecting in front of the wall (the mono fdn was overdug by kabuta), and down the ertical edge of it. Then the protective layer replaced. 

(I skip naming products at this time due to the tensions between companies)

Gravel and drain pipe will go back in place as they were, with additional gravel on top, instead of the clayey fill that was there. On top of that all around the addition at the same elevation the fill will be replaced with a specified soil that will help drain the area, instead of hold water, as clay does.

A better positive slope in the grading will be put in place than was done before.

Roof drainage during the construction period, before gutters go on will be directed away from the foundation and not allowed to collect in front of this wall.

Water tests will be done along the way with drying out periods in between. 

The waterproofer is redoing the membrane at no cost. The contractor and owner are doing the keyway/fill/water test.

---
I wanted to share this material, because I am impressed at how the engineer and contractors are choosing to optimize drainage and water stops for the mininal impact nearby and connecting drainage systems and waterproofing. Roof drain systems are in place underground nearby, complicating remedial measures which would move the pipes off the slab.

It is agreed that the mono slab fdn is not a good choice for underground slabs, and is worse in clayey soils. But even worse is the concrete ledge infront of the block, catching the water and ushering it at the horizontal joint. One step wosre than that, is that the drain tile was placed at slab elevation and not below it.

Now my only concern is whether the slab will stay put or shift, over time, when the drain tile is not below the slab. I wonder if the hydrostatic pressure at or below the slab will cause this. Because it is a daylight basement addition and the wall is short, there may be relief from this problem.

Any comments?

I really appreciate all the feedback and advice given here. We considered removing the contractor(s) from the site, but the current peak building season would have left us finding only the worst of contractors available for any followup until the Fall or later. The trickier parts of the job will be done per engineer guidelines by the owner, who is actually familiar with the work. The change in fill materials is apparently a tolerable burden to the foundation contractor, and he is familiar with the work. the reapplication of waterproofing is apparently a tolerable burden to the waterproofer and again a familiar piece of work.

I really think all the combined improvements could just make it past our problem.

What do you think?


----------



## wasdifferent (Dec 18, 2004)

J Hague,
You have shown great wisdom in getting a PE in there. You done good.

My only comment is this. If you hired me at this point, I would do everything in my power to talk you into getting a COMPLETE drainage system installed at an elevation below slab level. This is for your benefit in the long run. 

Also, the ledge on the outside of the foundation could probably be altered very easily so that it would have a steep slope to it, directing water toward the drain.

Please be careful that you don't end up with a fix that is marginal and works most of the time. Please think about this before you proceed. If you're going to dig, it probably won't cost much more to do a first class job.




> ...the current peak building season would have left us finding only the worst of contractors available...


It's not fun, BUT, you can get a good job out of a crew of 7 idiots, if you have ONE GUY on your job who knows what he's doing. This is coming from a guy who has been the ONE GUY, and has also been one of the 7 idiots...

I wish you much success, and VICTORY,


----------



## PipeGuy (Oct 8, 2004)

Nicely done. Talk to your PE about hydrostatic pressure concerns. I think there are better products than hydraulic cements and or a hard rubber water stops for fixes like this but they are both certainly within the mainstream of recognized means and methods. Again, nicely handled :Thumbs:


----------



## Teetorbilt (Feb 12, 2004)

In one of the last businesses that I worked for we had a licensed PE/GC. He used to brag about making $1K a day just signing and sealing other projects. Make sure that your PE is earning his $!
280 working days X $1K X 20+ yrs. = pretty good retirement for not doing much + retirement and bennies from regular job.
He's retired now and has cancer, maybe God caught up with him.


----------



## PipeGuy (Oct 8, 2004)

280 working days per year? Call me what you will - life is too short for that nonsense. The kids don't give a damn how much money you earn. What they'll remember is that you were always at work. Maybe it'll come back to bite me on the arse but I say 250 - 260 is plenty. Like they say, you can't take it with you unless you owe it when you go.


----------



## Paul B (Mar 10, 2007)

I think you are settling for a bandaide. If the drain is not along side the footing or wall below the floor, the problem will never be solved.

Sorry, didn't realize the post was so old.


----------

