Using Rubber To Waterproof a Flat Roof | This Old House

Tommy explains how to seal a flat roof. Then he and Kevin install a rubber-protected roof over an addition.

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Using Rubber To Waterproof a Flat Roof | This Old House

[glynnrobinson]

Although the basic installation is correct and fine for that area of the country. Tom mentioned wind uplift. The perimeter edge is the most vulnerable to wind damage. As an experienced roofer here on the coast of Wilmington NC I’ve seen roof damage from the results of multiple hurricanes. The biggest cause of low slope failures is because the perimeter edge failed. Drip edge should always be installed as tight to the facia as possible, as long as the face is less than 4” wide. Cleated if wider. We utilize a continuous metal cleat, the same profile as the drip edge and one gauge heavier, of the same type of metal or as we do, stainless steel for all cleats. It’s attached through the the face of the cleat just above the kick out with either screws or stainless steel, ring shank roofing nails, 6” on center. The drip is then hooked to the cleat at the bottom by an open hem. Then the drip edge is nailed on the roof side 3” on center in a staggered pattern. The roof may fail from other causes but the perimeter edge will not. Another thing I strongly disagree w with is the soft substrate. The high density Poly-iso is s designed cover board for the purposes of sphere ing membrane . Its about 80 psi in compressibility, regular ISO 20 psi. The harder the substrate the less damage from debris. EPDM is easily penetrated by falling debris. The softer the substrate the larger the penetration through the membrane. Harder substrates prevent bigger penetration and less damage. A gypsum board made for roofing applications such as DensDeck or SecuRock is the best protection from flying debris. Both these material also have the highest wind uplift resistance for any substrate if secured properly to the roof deck. For instance, 1/2’SecuRock over a 1/2” plywood deck with 18 plates and screw in each 4’x8’ board and fully and self adhered TPO membrane has a wind uplift resistance of -135 PSF from information gather from testing by our manufacturer. Ive been a fn since the show went on the air, I have the greatest respect for Tom. TOH is far and above any other in knowledge and professional building techniques. Roofing is my profession. Need another host? Seriously check into modern low slope roof design. It ain’t the hot asphalt I started in 40+ years ago. There’s some remarkable products and installation practices out there.

[samv]

Back in the 80's I learned how to do torch down roofing. On my first full roof, I was using the torch for almost 8 hours with a half hour lunch. That night I dreamed for what felt like another 8 hours that I was on that same job. I woke up feeling like I had just finished a 16 hour shift, torching down a roof. I went back to carpentry after that.

[MandoFettOG]

Very interesting, thanks for the full video

[JL-]

Finally something im better at than Tom!

[dandronemoan]

3:12 pitch is not flat! It's low-slope. Anything more than 2:12 CAN be shingled with the correct ice/water barrier. 4:12 is generally the break point where barriers are not required with shingles

[rickeykeeton]

Contact adhesive? How do you get any air bubbles out?
Do this big washers not cause problems?

[piabertone-gross]

In the process of designing a custom home for the southern coast of Maine (couple miles in from the ocean). It’s been an ongoing debate with my significant other weather it’s ridiculous to build a “flat roof” or even a “flat roof” with 1” slope per foot in New England. Responses from builders and contractors have been all over the map, for and against. Any insight on this?

[shenoyglobal]

What is the best way to waterproof hollowcore slab roof top terrace.. i wanted final covering to be natural stone..so what should go on top of slab and how to lay tiles at the end?

[scottjackson]

One critical question stands out in my mind. UV rays and nature (wind, water, heat, cold) would seem likely to degrade rubber rather quickly. I just want to confirm that there is no additional material on top of the rubber? If not, it would seem that the rubber will lack durability.

[dancooper]

In CA 3"1/2 and above is a pitch roof.

[MidnightsCorner]

"3 inches up over 12 inches, or 7 inches up over 24 inches"
Now I'm not a mathologist, but...

[alexf]

Any recommendations for a good roofer company in/near Hayward CA for residential house single story, low pitch. I have shingles installed before I bought house. Thank you for video

[whith]

so you extend the metal drip edge slightly out, to protect the fascia? wouldn't capillary action draw water up and under the drip edge then? or is the 45 degree angle enough to drive water off

[rockys]

What's the life span of that rubber? What happens when it breaks down and you need to replace it? Do you just cover with another layer?

[tpez]

We have a sunroom that is extremely loud when it rains heavily. This looks like it would really deaden the sound. Is there anyone in St. Louis that you would recommend to install this?

[strand]

My garage roof have a slope of 2 degrees.

[aniruddhdubey]

I need your help please let me know how I can contact you because you can only understand it better via images. Quick brief is we have a tree going through our glass roof and we need to waterproof the opening of the tree keeping movement of tree in mind via wind pressure

[bassplayermarty]

I have flutter (same type of roof) Does this mean they did not glue it down ???

[dancooper]

how do you install and waterproof a skylight on an existing torch down flat roof

[rookie]

Do you suggest a rubber roof liquid coating? EPDM?