Waterproof sheet system

Archive of Older Topics Archive - Product Discussions #3
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What is everyone’s experience using a sheet membrane system to cover a roof terrace? We have a roof terrace constructed of concrete on steel deck over an occupied space for a condominium project. The Owner wants the membrane to be patterned or stamped. The terrace is above an occupied space and will be insulated from the underside of the deck. The project is in the Chicago suburbs and subjected to freeze thaw. We are also looking at poured systems. Is one better than the other? Duradeck is one manufacturer we are looking at.

Thanks for any input.

2

the primary first issue is that any elevated deck (above ground level) over an occupied/finisehd space the membrane is a roofing membrane, not a waterproofing membrane.

You call it waterproofing on the drawings and the GC will be glad to give you a membrane with a 2 or 5 year warranty.

Elevated decks over occupied spaces are always roofing membranes. There are a few exceptions, such as a first floor lobby to a building that is under several decks of parking and the membreane (if its not a traffic coating) will be a waterproofing membrane). But these are rare exceptions.

As to sheet vs what, you need to state what the sheet is and what your default standard solution is. Peel and stick membranes are sheet membranes right along with PVC, EPDM, TPO and many others.

Chicago is the original home starting ground for hot fluid applied systems which are a perfect solution for any concrete surface so long as the concrete is not a lightweight fill, it can be lightweight structural concrete, that’s fine, and one hopes that is what is on the metal deck anyway.

So, if you are not doing hot fluid, my next recommendation would be a PVC membrane (such as Sarnafil). This is a great membrane and some of the manufacturer’s like Sarnafil can and do install roof membranes for dead level decks, water impounded, continuous immersion.

William

3

William,

Thanks for the info. Duradeck is a PVC membrane that we are looking at. I’ll check out the Sarnafil and hot fluid applied systems.

Thanks again.

Mark

4

I haven’t done many of these installations, but intuitively, I’m hesitant to use a sheet membrane on a plaza deck due to concerns with leak water migrating under the membrane. I just do not see any advantage that sheet membranes bring to this highly sensitive installation that cannot be better met with one of the hot fluid or cold applied rubber systems available in the market.

5

Here in South Florida, several hot applied liquid membranes are approved for use over habitable space and have great track records with warranties available up to 20 years (Hydrotech, Carlisle, Tremco), but we have also used Polyurethane WP systems like Neogard’s Pedagard that is available in a decorative version with a range of colors and patterns with warranties up to 10 years. I would tend to agree that we prefer a fluid applied system than a sheet membrane. Knock on wood, We’ve done 100’s of condominium projects and most of them have been specified with fluid applied systems. We don’t experiment on Condominiums, we prefer tried and true systems - so make sure you talk to a local WP Consultant and some trusted WP Subs and see what they recommend for your area.

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I’ll come down firmly on the side of fluid applied as well. In either case, fluid or sheet, be sure you do the ASTM D 5957 flood testing as part of your field quality control.

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George, If you spec the Flood Test for sheet membrane waterproofing, how do you know whether or not water has seeped under the membrane? We’ve had WP Consultants tell us not to specify the Flood Test for Sheet WP and/or Roofing systems. They say that they will be present for the WP or Roofing applications and don’t need the flood test for Quality Control; also they have a concern that water will seep under the membrane, esp. if there are multiple layers or protection board over the membrane, and the entire membrane will require removal to correct the problem.

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Mike, go ahead and specify a Flood Test, the main factor is to find out if it does leak, by a pin hole or seeping under the membrane. Being a person who handles both sheet & cold-applied waterproofing systems, the cold applied membrane has worked out best, because of less seams. You are waterproofing the plaza deck, use a approved waterproofing system material, this is what they do best, like the roofing membrane are best for roofs. Don’t forget to specify the membrane up the vertical side of the deck, you want to create a bath tub effect that waterproofs the whole deck, especially on the backside of the deck, by the door and wood areas.

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Impoundment test: I agree with Harold. Specify it regardless of types of systems. Find the leak now if there is one, the GC/sub pays for all the removal and repairs since this is the envelope and its not even substantially complete. Who cares what it damages. Find the leak later and it may be coming out of the Owner’s warranty limitations if it takes a long time to show up…or certainly the damage to other elements will prove costly to the owner during operation of the facility rather than before it is even substantially complete.

Waterproofing vs Roofing: I disagree entirely with Harlod and anyone else that may say this should be waterproofing and not roofing. You indicated that the deck is elevated (that is, not at ground level). You indicated it was over occupied space. That makes it a roof. Since it is being used as a deck area, you need to make sure it is a membrane that is capable accepting this installation. The Sarnafil PVC roof is, and so are most of the hot rubber roofing systems. What do you want, a 2 year warranty (or maybe 10 at the most) for waterproofing, or a 20-30 year warranty for a roofing system. Some very good membrane manufacturer’s, even some I actually use, will let you do whatever you want. But some will actually catch your error and change it to a roof for you. American Hydrotech is one of those if you engage them to review your drawings. But you can ask them on this point.

And further on this issue of waterproofing vs roofing - you are probably not even doing anything close to a garden roof (vegetated roofing membrane), and those are ‘roof membranes’ not waterproofing membranes.

Another point, some manufacturer’s actually warrant their roof systems from blowoff. Not so the waterproofing membrane.

William

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William, I’m not against roofers or roofing materials. I’m not sure what part of the country you are at, but I know let’s say Oklahoma the roofers DO ALL the waterproofing installations, but in Houston, TX I can show you a couple dozen apartment complexes where I’m called in to recommend a material or system. The company I work for gives a 10 year warranty if asked on ANY waterproofing project, as long as we can inspect the installation and have a pre-waterproofing conference to go over ALL aspects of the project prior to placing waterproofing membrane. We also manufacture the largest amount of roof walk protection panels for the industry. As far as blow off you have me there, the membranes we recommend are either sandwiched or adhered to the bottom of the deck. Maybe where you are at you feel more comfortable with a “system tried and true”, but since we have had success here that is my opinion for the Dallas/Ft.Worth/Houston/Beaumont areas.

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Harold,
Your post sounds as though you work for a manufacturer. Can you tell us which one, please? I’d like to know where William is based, too.

By the way, here in the Boston area, roofers and waterproofers are two different trades. I no of no subs here who do both. Waterproofers typically do joint sealants as well.

As far as I’m concerned, roofing and waterproofing lie at two ends of a single continuum. At one end is a simple big box low-slope roof–at the other is waterproofing of a tunnel. They both keep water above from coming into an occupied space. It’s just a matter of type of overburden and service conditions.

12

Yes I do work for a manufacturer that has been in business for 81 years now, my email address for work is hwoolard@wrmeadows.com which will let you know who I have worked for the past 30 years.

13

Great discussion. Here’s an interesting scenario, hopefully I can get some feedback (posted as anonymous because it’s project-related):

Drawings for a plaza deck with an occupied space underneath show a “roof system”, basically pavers+pedestals on membrane on insulation on concrete deck.

Specifications indicate a “waterproofing system” for the same construction, basically pavers+pedestals on insulation on waterproofing on the deck. Flood testing included in specs.

Naturally we have an RFI. Manufacturer’s rep tells me both are done all the time. ASTM D1079 defines “waterproofing” as “…treatment of a surface or structure to prevent the passage of water under hydrostatic pressure”. And “roofing system” as “…an assembly of interacting components designed to weatherproof, and normally to insulate, a building’s top surface”.

Sound’s like roofing by definition and spec’s need to change.

14

Harold and John,

WDG Architecture, Washington, DC and Dallas, TX are locations of our offices. All specs written out of DC where I am Associate Principal Specifications and Research, 24 years with them all as head of their specifications.

Our practice is high rise residential (both condos and apartments), office buildings, corporate headquarters, hotels, interior design, and a few other sectors we touch on.

Office is about 40 in Dallas, 140 in DC, architecture and interiors in both.

The Dallas office has projects around Dallas, Austin, Houston and in Colorado. The DC office has projects up and down the east coast, and we have done some design only work in Egypt.

Our typical membrane is hot fluid applied, American Hydrotech, Henry, Barrett for both waterproofing and roofing…though for waterproofing I will also leave it as a contractor’s choice to do Graces reinforced Procor system horizontally and Procor vertically. Secondary membrane, when someone really feels they have to have a single ply membrane is Sarnafil’s PVC (variety of thicknesses are available), and one of their typical applications is use as a pool liner.

In Dallas, the local fire marshal thinks the IBC prohibits the use of kettles (one of a few places in the country that has this prohibition) so in that jurisdiction we go with the Sarnafil. It can go in as a protected membrane system for roofing just fine.

I would not hesitiate to use either system in a plaza configuration over occurpied space, you will be able to get 20 year plus warranty that is a good quality warranty from either, though frankly, I think Hydrotech has one of the best and easiest to understand warranties out there. They act as a single source warranty for the entire system from pavers, pedestals (if used), insulation (retention of insulation value over time) to the membrane itself and its flashings.

My first project I was responsible for before I came here was National Geographic Society M Stree Headquarters building (DC). The entire site at grond level is filled with landscape and drive areas and the building is set back. But below the ground it is 100% lot line built out with museum storeage, museum work areas and soundstage areas for filming. Its all hot fluid applied waterproofing. The facade is stepped back planters where the planters are 1/2 extending past the floor below, and 1/2 over the occupied space, done as a roofing system. The systems are 30 years old, and no repairs. They were considering replacing the main ballasated protected membrane roof with a reflective energy star roof (the buildng became the pilot project for LEED Existing Building and they wanted to continue in that line). I suggested that they contact the existing membrane manufacturer since they have a program of coming out, recertifying the membrane, inspecting and perhaps raising flashings and going over from stone to pavers with a reflect coating in them or even a vegetated system over the existing membrane. After 30 years, the membrane looks like its only just cured.

William

15

Anon,

It really depends on whether the deck is elevated or not. If it is at ground level (or lower) its waterproofing. If it is above the first floor and over occupied space, it should be a roofing system with its much longer warranty. And a good roofing warranty will be single source and include the membrane, insulation, ballast (pavers whether decorative or standard or crushed stone) for removal/replacement and also, and warranty against blow off of any component.

William

16

ASTM D 5957 is “Standard Guide for Flood Testing Horizontal Waterproofing Installations”. The definitions quoted by Anonymous above come from ASTM D 1079 “Standard Terminology Relating to Roofing and Waterproofing”, which is referenced in D 5957. It occurs to me that the essential difference under these definitions is: where there is hydrostatic pressure it is waterproofing. After all the flood test does apply some hydrostatic pressure on the membrane.

To further quote from D 1079

“This guide is intended for waterproofing installation on parking garages and plaza deck type applications over habitable spaces or on elevated structures, but is not intended for use on building roofing systems. Applicable waterproofing membrane installations that may be tested using this guide are fully adhered or bonded sheet membranes, liquid or fluid applied membranes, or loose laid sheet membranes.”

17

one of the things I haven’t seen mentioned here in all this chatter is if the membrane is exposed or not. Most waterproofing membranes cannot take UV exposure. Traffic deck systems can take UV exposure and roofing systems are designed for UV exposure.
Traffic deck systems are not usually designed for very much foot traffic, and they often have to be reapplied on a regular basis, and the warranty isn’t as long as a waterproofing system. However, for a mechanical space, or a residential deck, they are very adequate.

my office has a standard of using Hydrotech (hot applied) for nearly every “roof” with pedestals over it, but its a waterproofing systemm, even though you can get a warranty from the deck up, much like a roofing system.

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There is no doubt that the heritage of Hydrotech’s membrane comes from waterproofing. Yet, the system the provide as a roofing system is indeed a roofing system, not a waterproofing system. It has a complete roofing warranty, for periods of time that ony roofing membranes (not waterproofing membranes) are warranted for. They market it as a roofing system as well. And they are very careful to assure that the correct system (roofing or waterproofing) is used in the coorect loctation - or that your intention is truly what is shown.

Its not ‘much like a roofing system’ - it is a roofing system. And the same generi membrane IS a waterproofing system. Go to their web site, they have very clear separeate paths, roofing and waterproofing.

And this is true of many of the other hot fluid applied membranes of the same generic type.

We use this system for the vast majority of all our applications - the majority of them having crushed stone ballast and only direct set pavers for walkways and wind related requirements.

William