Solving flat roof water problem

Discussion in 'Building' started by onionsa, 21 Aug 2020.

  1. onionsa

    onionsa

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    Ive always had an issue with water standing on the flat roof of my workshop. What would be the best way to fix this?

    Thanks
     

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  3. Notch7

    Notch7

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    I guess the outlet is on the right out of shot.

    Short answer is, the only solution is a new roof.

    If it's not leaking, do nothing until it needs replacement, then do the firrings correctly
     
  4. onionsa

    onionsa

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    It’s an extension to the garage and that has always had water on sitting on it at the back side so I’m pretty sure that’s not level either. The gutter is at the other end of the garage. If I get the roof relaid to slope towards the existing garage roof it will just sit there, so would it be best to relay sloping away from the existing roof and put a gutter this end?
     
  5. bernardgreen

    bernardgreen

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    Standing water on a flat roof has the benefit of reducing the effect of the sun's heat on the roof.

    Provided the roof membrane ( or felt ) does not leak then an inch or two of water will prolong the life of the roof.
     
  6. onionsa

    onionsa

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    That’s an interesting point. Could the problem be down to the fact that ‘top felt’ has not been put down yet? As I understand it there is only ‘underlay’ and a couple layers of blackjack roof repair.
     
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  8. Hugh Jaleak

    Hugh Jaleak

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    Fall (slope) on a 'flat' roof should be built into the timber, the felt is only a waterproofing layer. I suspect it would be difficult to build a fall into an additional layer of felt, unless the higher end was built up with several layers of felt, reducing to a single layer at the lower end. If you are to relay, I'd go with your idea to slope towards the foreground in the pic, and fit a gutter across the fascia there to collect the runoff.

    Normal practice is to spread white stone chippings over the finished roof to reflect the sun and protect the felt. (Looks like this has been done on the section to the right, just as it goes out of shot?)
     
  9. onionsa

    onionsa

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    Yes the original garage roof has white stone chippings on. I didn’t realise that also helped with protection from the elements, so that’s good to know.
     
  10. ^woody^

    ^woody^

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    If not stripping and relaying the deck , you'll need to lay concentric layers of felt to build up the dip so that water does not pond and is directed away from the corner.
     
  11. onionsa

    onionsa

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    Right so I've run through a few options and I'm looking to cut away some of the arris rail where the water pools and install a gutter to lead to a water butt. However, what I'd really like is a side exit hopper to keep things up and out the way as the water butt will be around the corner. Does anyone know if this sort of thing is made?

    Thanks
     
  12. DIYnot Local

    DIYnot Local

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