I’m wondering what (if anything) you have specified for underslab vapor barrier warranties. The question came up because our structural engineer wrote a 10-year warranty for an underslab VB into their cast-in-place concrete spec, which one of the bidders said could not be obtained.
A lot of times (but not this one), we do the underslab VB spec, so I looked into the manufacturers’ standard warranties. They range from lifetime of the building, to 1-year, to “call the manufacturer.”
On a more practical note… this sounds like one of those warranties that would seldom actually be claimed. You’d have to somehow prove the product failed by uncovering it (ripping up a slab) and prove it wasn’t due to improper installation.
Just curious what you all have done / seen, and if you’ve ever heard of a warranty claim on an underslab VB.
I don’t specify a warranty. My master specification software doesn’t even include it as an option. Neither does the Stego branded/written stand alone version of the section.
There is a value to specing a warranty if you also spec a product that offers one. Compared to just specifying a 6- mil visqueen vapor barrier, you will end up with a minimum 10-mil, maybe 20-mil, that is less prone to punctures, and requires specific taping along lap joinsts and around pipe and conduit penetrations.
I agree that if there are issues, enforcing the warranty will be difficult, but RH testing of really wet areas and GPR testing would likely find the source, at which point the concrete can be selective cut, the membrane repaired (under warranty), and the problem fixed. A spec or warranty cannot guarantee who pays for the fix, but it can lead to a better installation. With all construction, the install needs to be inspected and photographed.
Even if there is a warranty, does it include membrane materials only (omitting the cost of removal and reinstallation of the slab), or some sort of compensation for the fact that a top-applied remedial material may not perform as well as the underslab membrane?
I suggest that rather than specifying a warranty that may or may not be available from most manufacturers or installers, you spend the money on making sure that inspection of the vapor barrier is part of the building enclosure commissioning scope.
It’s always better to properly inspect important components that, as a practical matter, can’t be readily repaired rather than rely on a warranty. All of the product and installation points made by Dave can be specified up front.
The Owner’s sole remedy, should Owner meet all warranty requirements and also prevail in proving that the product is defective, is as follows:
Your sole and exclusive remedy under this Warranty is, at Stegos option: (a) Refund of the verified purchase price paid or (b) replacement of so much of the Stego Wrap Product as Stego deems necessary.
Anon’s post is proof that one (not just design professionals but Owners) should always read a warranty.
John,Greta- excellent points of doing an inspection, not just an observation. This is true for all structural componets (to make sure rebar is properly placed), envelope construction (openings are properly flashed, roofing is correct, different materials meet where they should, and sealants are correctly applied)- this also implies that the design details are correct- and for all Life safety items.
Unless it is additional material costs, including warranties with products that may offer them does not always necessarily cost more money up front. My point was that it will make the GC/CM and their subs more vigilent in their own work. Getting back to the warranty issue being for manufacturers, that is true, it protects them because they have so many ways ‘out’ of it. But if the specification also has the product installation instructions as a requirement, then the onus of the responsibility ultimately falls back to the contractor. Isn’t that why a design professional specs these things, to assign the means and methods responsbility to another party? After all we dont always detail these things clearly enough to properly build. It does take teamwork and communication.
I do want to go back to the initial post-
You can get a 10 year warranty (or others) if you specify a specific product, but if you are specifying a typical visqueen barrier, and taping penetration with non-proprietary materials (i.e. duct tape) then you will not have a manufacturer available to provide a warranty, and you would need to rely on the GC/CM to give you one. Probably not a good practice! If the visqueen- even if 10, 15 or 20 mil is installed correctly, sealed/taped, and penetrations handled correctly, then the system should perform as well as a proprietary system where all components are made by one manufacturer. If you go the non-proprietary route, it would be a good idea to include 3-d or axon details of the seam laps and penetrations, or a very good narrative describing these install conditions. This is typically what a proprietary system manufactuer will provide as installation isntructions.
Proving a failure? It will involve forensic work, will cost the Owner, and likley not be covered by the GC, esp. after one year. Litigating a claim like this, even more expensive. So inspection of the work before it gets covered is paramount.
Lightning protection systems often require LPS components to be adhered to or laid on roofing. The roofing manufacturer’s warranty typically says that anything applied to the membrane voids the warranty.
In new construction, the GC has installation drawings and other documents from both the LPS installer and roof installer, a pre-installation meeting, and other means to assure the two products are in alignment.
But how does this work if the LPS goes onto an existing roof? In an ideal world, the company holding the roof manufacturer will be cooperative and issue a letter or send a rep to the job.
Is there anything that I can put into the spec that will help out?
Thank you all! I appreciate the feedback. Definitely like the suggestion to not worry about the warranty and require an inspection prior to placement of the slab.
Greta, you are exactly on target.
I was just on site for a vertical waterproofing inspection prior to installation of the underslab vapor retarder and thought that all was copasetic. The following week I received photos of a beautiful slab-on-grade but no photos of the vapor retarder so I put in the request and was disturbed to see a “patchwork quilt” of membrane. Now we’re in wait-and-see mode. The installation may be fine. I have yet to review the concrete delivery tickets and obviously everything that happens in terms of finishing and curing can impact end results. Underslab vapor retarders are just one part of a bigger picture. This installation may be fine. I pointed out to the project super that it would have been less expensive to run the membrane continuously instead of spending labor hours taping intermittent seams. Now I wish I had stayed.
No warranty would cover this.
This is a commodity item. Spec the right product. Make sure it’s installed properly and protected. Most of us have preferences regarding products but feel free to specify an ASTM E1745 Class A sheet vapor retarder and call it a day. Add a thickness of at least 10 mils per ACI. I like 15 mils typically but it depends on the project and site conditions if we need something more.
Oh, please don’t let your structural engineer cover it with a granular fill blotter.
Dave: You are asking some really important questions. I used to share your position that polyethylene at a decent thickness (I settled on 10 mils just to keep the really thin stuff off of the project) should work just fine. But then the “lifetime warranty” vapor retarder manufacturer’s product rep showed be some physical samples of a polyethylene vapor retarder from a slab-on-grade core sample that was tattered and tissue-like and clearly not working any longer as a vapor retarder. It spooked me. I never specified polyethylene again, and took the reps word that his company’s product was designed and tested not to break down like polyethylene.
To Michael’s Point: Yes - underslab vapor retarders can easily and simply be specified by citing ASTM E 1745 with the Class desired, which becomes a performance specification (since the performance requirements are embedded in that reference standard). And this is what I have done for nearly 20 years.
Ken: It doesn’t matter if the vapor retarder was placed as patchwork. If the laps are of sufficient dimension (per manuf. requirements) it will work the same as if continuous. The purpose of an underslab vapor retarder is to retard vapor duffusion (vapor drive) from the earth side of the slab to the interior. Laps are tightly compressed and have no impact on ability to retard vapor diffusion. This is not an air barrier issue. Many of us on this forum have probably heard Lstiburek’s explanation of this: If a vapor retarder has holes in it adding up to 10% of the total area, it is still 90% effective as a vapor diffusion retarder, but if 10% of an air barrier is compromised - it is 0% effective. Don’t sweat the holes in a vapor diffusion retarder. Puncture resistance is a bit overhyped by the “lifetime warranty” sellers, IMO.
Yeah, but this application had multiple 3 foot wide trenches extending the width of the building where membrane was nowhere to be seen. Somehow I don’t think Dr. Joe would get a warm fuzzy from this one.
I’ve never asked for a warranty for a sheet product, but we sometimes use a below slab layer that ties in with the vertical waterproofing and the whole assembly carries a warranty. This would be comparable to a PrePrufe product which is installed to a thickness of 95 mils. This will carry a 10 years material warranty and a 5 year installer warranty.
I thought the “magic warranty” might be found with GCP (Grace) “FlorPrufe” 120, a lighter version of their PrePrufe waterproofing system.
No mention of a warranty in the GCP website.
I agree with the other posters about specifying ASTM E 1745 along with thorough site inspection.
I tell structural engineers to stick to structures and leave moisture control to the architect. That goes for ground emissions such as radon or hydrocarbons as well. It’s not the structural engineers job. I always specified underslab vapor and emission barriers as separate Division 03 sections, so they wouldn’t be overlooked when the concrete was placed.
It appears that there still exists a need for the architect to look at the structural drawings and coordinate. In my experience architects pay no attention to the need to coordinate membrane under slabs on grade.
Typically the structural engineer has a detail for slab on grade. This detail references the subgrade as well as the concrete and thus should include the membrane between the two. If this detail does not address the membrane I suggest you will get no membrane even if shown on the architectural drawings. Thus the need for coordination.
Because of the lack of coordination by architects many of the details used by engineers reflect the practice of 30 to 40 years ago.
Recognizing that there may be situations where an effective sub slab membrane may be needed I am going to suggest that in most instances this is not a problem that causes long term problems. If I am wrong given my awareness of what has been constructive I would be expecting massive problems with slabs on grade. But I fear that the problem is no way near massive.
The moisture tests are misleading. I believe that what they recognize is the moisture in the concrete and in general not any moisture from the subgrade. Further if you have un-cracked concrete the concrete will not pass enough moisture to the surface to fail the moisture test.
If there exists a high water table and hydrostatic forces the world may be different.
A warranty that does not address the cost of replacing the slab and other work is worthless. The cost of the membrane is a relatively small amount. In this context it does not make any sense for the membrane manufacture to provide a comprehensive warranty.
As an aside it might be useful to discuss when a warranty is appropriate. Does it make sense to ask for a warranty for reinforcing steel or for the aggregate used on the project.
Mark, as noted in many articles, failure to provide a vapor retarder or barrier or membrane (our industry likes using multiple terms interchangeably) tends to result in moisture vapor permeating the concrete and affecting the interior installation. Typically this is most noticeable with finished floors that fail since most water-based adhesives will revert when the vapor gets trapped and condenses. Unfortunately this happens quite often.
The underslab membrane is the first step in preventing that occurrence. Of course water-cement ratio, water of convenience, and curing methods have as much bearing on failure as the vapor membrane does.
I agree that the membrane should appear on the structural drawings. I don’t care who specifies it but as you note, please coordinate. I can’t tell you how often I see 10 mil vapor retarders shown on Architecturals, 15 mil vapor barriers on Structurals, and 6 mil poly from Home Depot on site because no one bothered to see what was being used.