Poly not overlapping at bottom of beam

[Richard W. Washington]

Is not overlapping the poly at the bottom of the grade beam correct depending on what part of the country you are? I had someone from the country of Dallas tell me (from the country of Houston) that it was.

this is my first crack at uploading a pic so hopefully it comes through.

[Emmanuel J. Scanlan]

Hello Richard,

We know the purpose of a vapor barrier is to help prevent wicking of water into the slab. Water not only affect the concrete but also any flooring material cemented/epoxied/etc. to the floor. I always expect the vapor barrier to be overlapped, including in the grade beam area. Without the overlap it degrades the intention of the vapor barrier.

Now if you go to the TRCC site they do use the Texas Section of the ASC document Recommended Practice For The Design Of Residential Foundations
http://www.texasce.org/docs/DesignGuidelines.pdf . Here they leave the decision up to the engineer designing the foundation. The design engineer is responsible for the complete design from interpretation of site survey results through to placement of concrete.

It would be interesting to hear other viewpoints. Also if anyone has a link to a copy of the latest PTI standards that would be nice.

[Marcel R. Cyr]

I might be mistaken here, but looking at the picture, it almost looks like they installed a little bit of dirt after the poly was installed to hold it down in the depressions.

Marcel

[Larry D. Kage]

Originally Posted by mcyr

I might be mistaken here, but looking at the picture, it almost looks like they installed a little bit of dirt after the poly was installed to hold it down in the depressions.

Marcel

That's what I was thinking, too, Marcel. Notice how the poly is taut along the edges of the grade beam walls?

[Barry Adair]

Rich,

I concur with MC and Kage, non-native "sand ballast", very different from the common soils in your area, in a "very clean" installation rarely seen where I've been.

Maybe they are learning that the foundation is the most important aspect. Also agree with Manny's statements.

Manny,

I'll see what else I have to send you later


Here is one example of what you really don't want to see.

[Emmanuel J. Scanlan]

Barry,

Gee, that looks like a typical build up my way!

I'd appreciate any info you may have.

Yes I do agree it could very well be ballast. With that in mind, there are varying thoughts about placing cushion sand on top of the entire vapor barrier before pouring. Not as a ballast method but as a leveling and cushioning method. Any thoughts out there as to the usefullness of that?

[Richard W. Washington]

Is the poly not placed across the bottom of the grade beam up in the Dallas area? I spoke with the engineering company from Dallas that designed this foundation and they said that is the way it is done around there. Down here I've never seen this done until this particular builder. This is a large volume national builder too. My question is this correct when down here on the Gulf Coast we have expansive soils an a high water table? There is going to be quite a bit of percolation through the slab w/out the vapor barrier being installed to overlap the required 6" at joints.

R506.2.3 2003 IRC
A 6 mil polyethylene or approved vapor retarder with joints lapped not less than 6 inches shall be placed between the concrete floor slab and the base course or the prepared subgrade where no base course exists.

[Emmanuel J. Scanlan]

Richard,

Thanks for the IRC reference. I knew it was there but did not find it.

In Texas new home builders are required to follow the IRC and part of your answer is in that reference. Not sure exactly where the property is that you are citing (in Houston?). Houston's building codes are not available online from what I can find. The IRC exception 3 to R506.2.3 2003 IRC does allow the BO to make a determination on whether to add it or not. If the Engineer approved that, and the BO agrees, then it is allowed. You would have to obtain the foundation engineering plan and BO/local codes info.

In this neck of the woods I have not seen any local codes specifically allowing it. If I see it and it is not ballast (as the others appropriately called out) then I would write it up and advise the client to have the builder show them the Engineering plans or BO approval. Or you could approach the builder for the engineering plans and review it yourself.

[Richard W. Washington]

Originally Posted by escanlan

Richard,

Thanks for the IRC reference. I knew it was there but did not find it.

In Texas new home builders are required to follow the IRC and part of your answer is in that reference. Not sure exactly where the property is that you are citing (in Houston?). Houston's building codes are not available online from what I can find. The IRC exception 3 to R506.2.3 2003 IRC does allow the BO to make a determination on whether to add it or not. If the Engineer approved that, and the BO agrees, then it is allowed. You would have to obtain the foundation engineering plan and BO/local codes info.

In this neck of the woods I have not seen any local codes specifically allowing it. If I see it and it is not ballast (as the others appropriately called out) then I would write it up and advise the client to have the builder show them the Engineering plans or BO approval. Or you could approach the builder for the engineering plans and review it yourself.

Emmanuel, the reason for my Dallas reference in the original post is that the Engineering Plans, which I grabbed from the formguys on site, had a Dallas area Engineering co listed. Their is no BO since this home is in an unincorporated part of the county outside of Houston. So all of you Dallas area guys (Emmanuel, Barry, Nolan, etc.) have not seen the poly left out of the bottom of the beams?

[Barry Adair]

Originally Posted by rwashington

So all of you Dallas area guys (Emmanuel, Barry, Nolan, etc.) have not seen the poly left out of the bottom of the beams?

Rich,

The answer is is yes, I often see no VB overlap and no VB throughout the bottom of the beams. (See my pic above)

Noted as an item t be repaired before concrete installation.

Does it ever get addressed to my clients satisfaction?

Occasionally when they have raised a big enough stink, the time to show up the day of the pour, or hire me to video tape the pour with the deficiencies unrepaired and still present as the mud's-a-flowing.

1 client switched lots, 1 builder buy-back, and have another that is under further review by the suits to seek damages.

[Emmanuel J. Scanlan]

Richard,

As Barry stated it does happen frequently and is written up as such. I even had a builder try it on me when building a steel building on my property. I refused to allow him or any concrete trucks on my property until it was corrected. Unfortunately all that can really be done is to document these incidents as the client, not the Inspector, is the only one with the authority to prevent it from moving forward.

Just like any other Inspection junkie out there I look at every foundation I drive by just out of interest. I see it quite a bit on many of those foundations.

Just out of curiosity, did the engineering plans make any note of vapor barrier placement?

[Nolan Kienitz]

Rich,

My "lack of poly" in the grade beams is almost always consistent ... in that it is not there!

When I was living/inspecting the Houston market I seldom saw it in the beam down there as well.

My experience in the DFW market the past two years has been one of trying to convince (either with my help or the buyers) the builder to get a 'full wrap' on the pad itself.

A large majority of the builders just don't care or they don't monitor their individual trades or the local city inspectors don't care or don't know or Lord knows what.

Cheers,

Nolan Kienitz, PMP
Nolan's Inpsections, LLC
http://www.NolansInspections.com

[Robert J. OConnor]

If that isn't sand/fill added over poly at the base of the grade beam trench, consider this.

The IRC R506.2.3 provision applies to concrete floor slabs on grade, and not necessarily to grade beams (which could be considered part of the foundations covered under R403, and not a concrete floor slab covered under R506). Also note that the requirement doesn't apply to unheated/unfinished areas, and R506.2 states the requirements of that section apply to "The area within the foundation walls".

The real concern is that water vapor will migrate up through thin slabs and possibly damage floor finishes like glued vinly tile and carpets. Water vapor is less likely to migrate up through much thicker foundation grade beams as compared to relatively thinner concrete floor slabs.

I am not saying either way is definitively right or wrong, but just giving another point of view to consider.

Originally Posted by escanlan

In this neck of the woods I have not seen any local codes specifically allowing it.

Keep in mind that codes are generally "restrictive" standards, and not "permissive" standards. Meaning it is technically allowed unless addressed by the codes.

JMO & 2-nickels ...

[Marcel R. Cyr]

Well in my book, this would be the smallest grade beam I have ever seen.

And I would have to say that yes, this slab depression needs to have a continuous vapor barrier.

Marcel

[Robert J. OConnor]

Originally Posted by mcyr

Well in my book, this would be the smallest grade beam I have ever seen.

Here's where the water gets a little muddy. Is that considered a foundation grade beam? In my book a small one, but a foundation grade beam none the less. Some may consider that just a thickened slab (similar to a commercial "waffle slab"). Coundn't resist MC ...

I think a lot comes down to what the local AHJ or designer thinks, and what the typical local practice is.

JMO & 2-nickels ...