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Discussion Forum

Best way to repair flat roof and possibly add a deck on top

Seaside72 | Posted in General Discussion on January 28, 2022 01:44pm

Hi! I just purchased a historic home that has a large porch with a flat roof and that roof serves as the floor of the second floor porch/deck. The flat roof leaks like crazy (water pouring in to the vestibule below and the roof of the 1st floor porch). Just got one contractor to come give an estimate for the flat roof. This is what he described and just wanted to double check if it seems like the best protocol: remove what’s there, put down plywood, create a slight grade (about 3 inches high near the house) and then put these 15 by 25 black rubber sheets down and seal the seams. He said to put decking on top we would need to be careful not to puncture the rubber with screws or else the warranty would be void. Does this all sound like the best way to approach it? I’m also wondering how much damage there is to any structural components of the home underneath because the water damage has been so extreme. The water has been going all the way down to the basement. The vestibule has signs and smell of mold. Thanks! (Only one of my pictures attached. This shows the door to the second floor deck)

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  1. User avater
    sawdust_steve | Jan 28, 2022 02:04pm | #1

    You are not going to know the extent of the damage untill you rip out the old roof. Thats the way things are in constrcution there really is no way of knowing.

    The best roofing system for a flat roof is EPDM (rubber membrane) some older guys may still be using sheet goods/tar so just doublecheck. Your best bet to check the requirements for a deck over the roof is to search the manufacurer's recommendations so find out the brand of roofing your guy wants to use and then make some calls or start googling.

  2. coldinohio | Jan 29, 2022 09:49am | #2

    Sawdust Steve has great advice. Once you get extent of damage you can check to see available options. I have seen some pvc floating decks over rubber membrane. No drilling through membrane, additional layers of membrane under deck where needed. Also have seen type of flat roofing material that is made to support chairs, tables and foot traffic. Would not feel comfortable doing that on just the rubber membrane. Please let us know how this proceeds

  3. User avater
    2sheps | Jan 29, 2022 10:19am | #3

    About ten years ago I was hired to remove the tin from a flat porch roof on a two hundred year old house. The owner had me replace the minor damaged t&g sheathing with modern plywood. Then a roofer applied a glue down rubber membrane. Since that time, the roof has been repaired or replace at least once and has leaked badly causing extensive damage to the porch framing and even trim work below.
    I would strongly recommend using something more durable. Perhaps flat metal. I've seen these done with copper too, with soldered joints but I know this would be a very expensive option these days.

  4. fsmyles | Jan 29, 2022 04:25pm | #4

    We used to use EPDM roofing but have changed over to a liquid applied roofing such as Sikalastic:
    https://usa.sika.com/en/construction/liquid-applied-roofing.html
    or Kemper:
    https://www.kemper-system.com/CA/eng/

    Seamless. Can easily accommodate afterthoughts and penetrations. Durable. Done.

    Frankie

  5. mikemahan3 | Jan 29, 2022 10:58pm | #5

    I’ve been using Westcoat products for quite a while with good luck. https://www.westcoat.com/

  6. Seaside72 | Feb 11, 2022 12:40pm | #6

    Thanks everyone! Frankie, do you know any contractors who do the liquid applied roofing in Connecticut? Is that something we could do DIY? Do all on this thread agree that any of these cases we would want a slight grade to the roof? Mike, I checked out the Westcoat website. Is there a specific product on there you think would be good for this situation? I'm attaching a picture of what the original house looked like. It's the porch with the awning that is leaking. The roof on the next level up with the little railing is also leaking a bit on the seam. Got the quote back for the company that does the strips of rubber membrane and it came out to $7,000 for the porch with the awning and fixing all the gutter downspouts.

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