Asked on Dec 9, 2012

What is the best spray waterproofing for new roof construction. I'm thinking a spray TMO could be quicker during bad we

Reliable American Inc.Terrie KaufmanBoss construction and roofing


I have a new SIPS roof going up just before Christmas. Living in Indiana, bad weather is sure to hit anyday. I'm looking for a substitute to felt paper or Ice & Water Shield that may be less expensive and just as effective. What options exist that are proven? My neighbor years ago, used to coat his shingles with a sprayed on tar. Will that work? I have no attic space in this home, as all the walls and roof are 100% SIPS.
10 answers
  • Less expensive - you won't find one As effective - sure some of the rubber based waterproofing system used will be just as effective as I&W properly installed but there will be some serious tradeoffs & possible moisture issues The optimal solution - use I&W as required by code & the manufacturers directions and include all the seams. Then go over it with a product like Titanium UDL --- both products should be installed with cap nails, NO staples Done properly it would take hurricane type winds to rip it off & cause leaks

  • Hamtil Construction LLC
    on Dec 9, 2012

    Guy, is the motivation to get it weathertight ASAP, or to save money? As SLS suggests, you will not find a cheaper product than felt paper. I would stick to the recommended and proven methods. We use I&W around the perimeter and on low slopes, sometimes in valleys also. I have not personally seen paint on waterproofing used as a roofing underlayment, and I would not want to be the first to try it. I would be nervous about the material breaking down over time with heat, and also the risk of moisture issues.

  • I would stick with ice and water shield. Your going to need to put something on the roof anyway under the shingles. If you get the GAF Ice and water shield stuff that has the granules on the surface, It comes in 1 square at around $48 each. you can get about six months exposure before you need to cover. The spray systems are ok, to a point, but you will still need to cover that when installing the roof. So the money spent putting spray asphalt coating would be lost once you install the Ice and water shield or tar paper later on.

  • Guy East
    on Dec 10, 2012

    I understand the reliability of the Ice & Water Shield. But on an 8-1/2" SIP roof, R50, it would seem as if some vendor would have created a quick and reliable spray applied waterproofing. If I have 5 days of sun and warmth around Christmas in Indianapolis to install 6000sf of I&W, which is 1200sf per day with drip edge, on a 10/12 pitch, I wouldnt be considering an alternative. Why can poured basement walls be sprayed but not roofs? I could probably have my roof sprayed in an afternoon.

  • For the first part, the codes specifically call for I&W at certain locations Might a code official allow a rubberized coating instead - possibly Should they - Probably not, especially on a 60 square roof as to my knowledge it has never been tested (especially with SIPS) and if there is any moisture or dirt on them it can spell some big issues. Along those lines the products above are designed for nail penetrations whereas the coating isn't - might it work... possibly The alternative I gave you above does not take that long to install especially with a cap gun nailer. The rolls of Titanium UDL are not only lighter, but taller & you can cover 4 squares at a shot as I recall. Also by sealing all the seams beforehand with I&W ensures that even if the Titanium got ripped off (or you didn't get it all installed) you wouldn't have moisture issues with the seams plus it blocks any air infiltration issues there Would a rubberized coating be a cool alternative - sure, but I would rather try it on a shed or garage first to see how it works out

  • KMS Woodworks
    on Dec 10, 2012

    I have seen 4 to 5 thousand sq ft roofs being completely shingled in a day or two. It just takes roof top delivery, and a decent sized knowledgeable crew. One man with a ladder with a box of roofing nails and a not going to cut it. The Adhesive nature of Grace I & W shield works great and can be laid very quickly without nailing. While not ideal winter roof installs can be tricky, in my area this type of work is scheduled for early summer. This allows for a proper thermal set of the shingles before our 80 mph winter winds come.

  • The issue with the spray on water proofing coating is it is not all that flexible. It does stretch a bit, but it is designed to be very thin coat so it can move, but with a roof there are gaps between the plywood that open and close every time the sun comes up and goes down. IT works well on CMU because there is little to no movement due to heat and humidity as there is with wood. This is the same issue with sealing brick chimneys, Lots of products out there, but they simply do not bridge the gaps between the cracks. Allowing moisture to enter and destroy the bricks. There have been roofs sprayed with foam sytems. This water proofing system works well. It is then coated with a sun UV blocker to prevent the foam from deteriorating. The only issue is once its down, and eventually needs to be replaced. It is a dog to remove. I have worked on a few of these on commercial flat roofs, It was a nightmare cutting our HVAC ducts through the roof and then sealing again. Stick with the tried and true methods.

  • Polyurea can be sprayed. about $3-4 a sqft. go with I&W and shingles.

  • Terrie Kaufman
    on Dec 11, 2012

    What about rolling on Super Deck ?

  • Reliable American Inc.
    on Dec 18, 2012

    Spray on tar? Hmmmm there are numerous types of roof coatings and tar emulsion is one of them, but not likely a handy home owner has access to such a product. Hopefully he wasn't simply spraying on drive way sealant. Just because he did it, doesn't mean it was right or that it accomplished anything either. As a professional roofing contractor in the Chicago market, I have never coated an asphalt shingle roof, and never would consider it with the products on today's market. Onto your problem. You have a sips roof going on. What is the substrate of the sips? Is it a plywood or osb substrate? If so these absolutely must be protected from moisture, ESPECIALLY osb. Why not install ice shield and felt? It's not 100% but I think would be far superior to any coating you could apply to the wood. Furthermore you would have to tape off all the seams in the SIPS panels or water will penetrate between the cracks if you were strictly looking for a temporary solution before the shingles could be installed.

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