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Flashing question

Discussion in 'Roofing and Guttering' started by sotal, 10 May 2020.

  1. sotal

    sotal

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    We have a small tiled roof over our porch/bay window. It was originally built as a flat roof, then a previous owner put the tiled roof over the top on a slope to improve aesthetics (probably in the late 80s). Unfortunately they didn't put proper lead flashing on. They just put some very thin flashing tape on which must have had some kind of bitumen backing as that has seeped out in the heat over the years. This flashing tape has degraded to the point where it has holes in it now.

    I did some flashing a good few years back alongside a roofer but have forgotten a lot of that now!

    So I was going to replace it with lead flashing.

    I've had a quick look today and just wanted to check a few things.

    1. Size. I know the guidelines tend to be 6" up the wall and 6" down the slope. However this is quite a small slope. It is 5.5m wide but only about 1.5m up the slope. The tiles also do not get that close to the wall at the top. They sit about 2.5" away from the wall. If I continue the slope to the wall virtually, then there is a nice mortar line 4" above which I was going to rake out. On the slope I was going to go with 6" which would be 2.5" over the gap and then 3.5" over the tile. Would that be enough? That would be approx 250+20mm to go in the mortar gap. So I'd need 270mm wide if they do it that size.

    2. Material. I hadn't realised how much lead flashing cost! Are any of the alternatives worth looking at? I've always had the fact that you could see this stuff was rubbish that is on now. I wouldn't want something that looked obviously wrong. Would prefer to pay for lead but just checking that I want missing something just as good.

    3. The ends. Last time I did anything like this. I made the lead a bit longer than the roof and cut a large v shape into the side which allowed the vertical part to go out at an angle and the slope part to fold round the edge of the tile. With this roof the tiles actually go a few mm past the edge of the wall. Do I just finish the vertical section at the edge of the wall and then overlap the tile or do I lap the lead around the corner of the wall?

    Thanks!
     
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  3. 23vc

    23vc

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    1 sounds ok, you’re looking at a roll of 300mm code 4
    2 use lead
    3 not sure what you mean, draw a sketch?
     
  4. noseall

    noseall

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    In this instance you would maintain the vertical part of the lead right down to the gutter or the end of the tile. You form a tapering free standing up-stand on the lead that keeps the water from going over the short bit of verge..
     
  5. sotal

    sotal

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    Thanks for the replies, I found somewhere online that does 270mm wide code 4. If I did go for the more widely available 300mm, would I adjust to make it fit or cut it and use the scrap to make the wedge things to hold it in place?

    I'm thinking of getting a 6m roll and cutting it into 1.2m lengths. With a 100mm overlap it should fit with 100mm spare. At that rate if I get the 270mm I won't have much spare to make wedges but could just buy clips instead.

    I'll try and get a photo to explain the ends
     
  6. 23vc

    23vc

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    Can’t you just dress more of it over the tile? or as you say just cut it
     
  7. oldbutnotdead

    oldbutnotdead

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  8. sotal

    sotal

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    Right, I've purchased a 6m roll of 300mm code 4 lead, and a bag of hall clips.

    I'm just trying to decide the way that will look best.

    I've attached a picture below - which gives the two basic options. I have marked them in red and blue - they aren't exactly to scale and the angle of the camera makes the slope look shorter than it is.

    The red one would have approx 3.5" of lead vertical, and approx 8" down the slope of the tile.
    The blue one would have approx 6" of lead vertical and approx 5.5" down the slope of the tile.

    The current nasty flashing tape is about 6" wide, so the flashing is going to look a lot bigger.

    I'm edging towards the red looking better. Do you agree?

    The final option would be to cut it, but I guess it is tricky to cut along the length?
     
  9. sotal

    sotal

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    Sorry - forgot the attachment...
     

    Attached Files:

    • roof.jpg
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  11. 23vc

    23vc

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    Blue. Red doesn’t have enough upstand
     
  12. datarebal

    datarebal

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    red looks like 75 mm? in which case its fine
     
  13. sotal

    sotal

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    Just over 85mm for the upstand if I go with Red.

    I'm still undecided. I think 6" of upstand will look like a big thick strip compared to the size of the roof.

    I've taken the top row of tiles off today, cleaned off the bitumen and the flashing tape, removed the silicone that ran across the wall, and put the tiles back.

    Next job is to rake the mortar and then fit the lead. The mortar rake hasn't arrived yet though (I did order in plenty of time but the first seller sent the wrong item).

    I might cut the lead up into shorter lengths ready.

    I need to make that decision on blue or red!
     
  14. datarebal

    datarebal

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    It's your choice , 75 mm is within realms of good lead work
    A very important thing is chase the joint out well.
     
  15. sotal

    sotal

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    It really is just the aesthetics that matter.

    The pitched roof has plastic sheeting underneath should any water get through, then if it got past that, the old flat roof looks to still be in good condition underneath and that has some kind of lead guttering leading to an exit pipe. There has been a big hole in the flashing tape that was on before for the last couple of years and we've not had any issue.

    However that said - I still want it to look right and to function correctly.

    I'll be chasing the joint out well. I have setup good secure access which should make it easier.
     
  16. sotal

    sotal

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    I just noticed that the tiles on that part of the roof go in a straight line, does that matter? The same tiles on the main roof overlap by half a tile. Obviously they've been in a straight line like this for somewhere around 30 years but should they overlap? They have quite a large interlocking part which should channel any water straight down so technically I can't see a problem.
     
  17. datarebal

    datarebal

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    marley moderns generally are half bonded. There are plenty about straight bonded and it will not cause a problem other than looking naff
     
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