Shed roof repair advice needed

Discussion in 'Builders' Talk' started by action711, Oct 27, 2013.

  1. action711

    action711 New Member

    Hi All,

    So I have a brick building with double glazed doors/windows at the bottom of the garden. It has a flat roof and is about 5m x 3m. A decent size.

    There was an overgrown bush growing up the sides and covering it's roof, which I've just removed.

    There is damage to the roof consists of where the bush's tendrils (?) grew up the side of the building, under the waterproof coating, and grew through it, poking through the corner of top and side. Kind of all along one side it's quite bad and the bit of protective coating that went over the side is breaking away, cracked at the top. It's also got a few patches like this along the back, just a few areas where the bush is slightly breaking through, but not cracked all along.

    So I've removed all the bush, it will no longer grow and make the damage worse. The rest of the roof is solid and fine. The coating I don't even know what it's called. It's like sheets of quite hard stuff, with fine gravel stuck to it and looks like it's tarred or stuck down with bitumen maybe....I don't know, I work in IT!

    Oh, there's a bit of wood along the side which is rotting.

    Now I don't want to repair the whole roof, just need to patch it, but how?

    Thanks for reading
  2. Are the sheets perfectly flat? And can you see horizontal 'joint' lines running around every 900mm or so?

    In which case it'll be standard mineral felt - the most common material for flat roofs on sheds, etc.

    In which case, you need to buy some more... You can get this at Builders' Merchants or Wickes or Superstores such as B&Q or Homebase, etc. And it's usually fixed using adhesive such as

    However, the bottom sheet (which I guess is the one that needs replacing) needs to slip under the sheet above, so's water running down t'roof flows over the joint.

    If the current sheet is stuck down with adhesive or bitumen, it'll be a pain to remove without a powerful blowtorch.

    Depending on the damage, or how visible it is (will it be an eyesore?), you can get some very good roof sealer these days you can brush or roller on, and it'll likely last as long as the rest of your felt. Stuff like:

    If your roof sheets are corrugated, then what you have is something like 'Onduline' or other bitumen-based roofing sheet. In which case they'll be held down with bolts, screws or nails, and the sheets will run up t'roof vertically.

    (You could add a photo - that always helps.)
  3. action711

    action711 New Member

    Thanks for the advice.

    I checked out the felt are Homebase, but my material is def a level up from that.

    I painted a sealant over the damaged areas for now. Will do a more solid repair with felt and tacks and sealant later.

    Not sure what you meant "about under the sheet above" - how can I do that? I thought instead to seal the edges of the repair felt, when I do it.
  4. "I checked out the felt at Homebase, but my material is def a level up from that." No surprise there! Good chance that your felt has been professionally applied by coves using torches.

    What I mean about the overlaps is, these rolls of mineral felt are around 900mm wide (I think), so to cover a higher roof slope than this you obviously have to use more strips. The felt is rolled out and fixed horizontally, with the first strip being laid at the bottom eaves, with enough overlap over the bottom edge to allow it to be fixed around the edge, wrapped, whatever.

    This strip is fixed down using whatever - adhesive for a proper finish, torched-on bitumen adhesive when pros do it (tho' this is becoming a bit 'old school', I understand), or even felt nails (short, with large flat heads - and galvanised) on cheapie garden sheds.

    Then the next layer is rolled out above this one, but it must overlap the top edge of the one below, so that water running down the roof flows over the join and doesn't have to rely on it being a perfect 'seal'.

    Does that make sense?

    What sort of sealant have you used for the repair?
  5. For a temp repair, Acropyl.
    Next spring rip the lot of and fit an epdm roof.
  6. Mr. Handyandy

    Mr. Handyandy Screwfix Select

    Be careful if thinking of putting any 'shed' felt of lower grade over the top of the higher grade.
    The grit on the thicker felt are larger enough to go through the cheaper, thinner stuff.
    One footprint up there=80 tiny little perforations in top (thin) felt!

    Mr. HandyAndy - Really

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