Leaking Shed Roof

[Andyc0081]

So, I have a fibreglass roof in my shed that is fixed to a pebbledash wall (that our shed and our neighbours shed share. And there is a lot of water ingress, but it looks as if it’s coming from the joining. I’ve peaked below the fibreglass flashing and looks as if even underneath that there is some type of sealant but the waterproofing is failing on both levels. I need this watertight as we’re boarding it out and having electric wired in. How do I make this watertight?

As a side note it also looks like there are slight patches of water ingress in different parts of the pours concrete sections, can I seal the inside or outside (outside is pebbledash). Just keen to make this whole thing completely watertight before boarding it out.

 

[Mr Chibs]

You’ll probably get some good replies if you post some pictures.

 

[Andyc0081]

Photos now attached, I had initially thought where the end bit of flashing had come away from the main flashing was the issue but now that’s it’s been heavily raining the water has come through all across, does the bottom of the flashing need sealing or does it need more sealant along the top? I’m really not sure what to do

 

[Mr Chibs]

I’ll start the ball rolling.

Good photos btw.

I suspect the flashing (upstand) joining the wall is the likely culprit.
I’m guessing under this flashing, the roof covering is just touching the wall, water could be getting under this and Bosch.

really the flashing wants removing and you’ll then see what’s what.

If you are not inclined to remove it, you could try using Flashband, you can get a 225mm x 10m roll for around £20.

Bend it in half lengthwise, apply to dry surface, by peeling of backing and press down firmly as you go, I use a cloth and/or a rounded bit if wood ( you don’t want to pierce it). You can probably get 100mm width on the Upstand and the rest on the roof.

Works best on a sunny day, or when you’ve warmed it.

 

[Bosswhite]

Its possibly that the flashing is not wide enough and lifted, I notice there appears to be gaps between the flashing and fibre glass due to expansion . , I would be tempted to re silicon all areas and fix a Wide Band Flash band on top of the exsisting flashing .

 

[Andyc0081]

I’ll start the ball rolling.

Good photos btw.

I suspect the flashing (upstand) joining the wall is the likely culprit.
I’m guessing under this flashing, the roof covering is just touching the wall, water could be getting under this and Bosch.

really the flashing wants removing and you’ll then see what’s what.

If you are not inclined to remove it, you could try using Flashband, you can get a 225mm x 10m roll for around £20.

Bend it in half lengthwise, apply to dry surface, by peeling of backing and press down firmly as you go, I use a cloth and/or a rounded bit if wood ( you don’t want to pierce it). You can probably get 100mm width on the Upstand and the rest on the roof.

Works best on a sunny day, or when you’ve warmed it.

Thanks for this, is there a certain brand you would recommend that would work best on the pebbledash wall? And would you do anything to prime the wall or flashing first?

 

[Andyc0081]

Its possibly that the flashing is not wide enough and lifted, I notice there appears to be gaps between the flashing and fibre glass due to expansion . , I would be tempted to re silicon all areas and fix a Wide Band Flash band on top of the exsisting flashing .

thanks, in terms of the silicon, would you apply to the flashing where it meets the wall AND where it meets the roof?

 

[Harry Bloomfield]

Not my area of expertise, but might it be almost impossible to get flashband to stick and seal onto an uneven surface of pebble dash. Might it be better to clean it down first, then add a skim of mortar to make a flat smooth surface?

Asking, not telling!

 

[Mr Chibs]

Yes, you won’t get it to stick to the dashing, I was meaning on top of what’s there. As a quick (possible) fix.

Looking at your images, it looks like the upstand is well fixed to the dashing, unless you say otherwise? So perhaps the leak is where the upstand meets the roof??

I used Wickes flashband, seems to have done the job.

 

[foxhole]

Problem would appear to be that upstand is only fixed to dashing which will let rain pour down behind it, dashing has to be removed to cut in upstand (ideally lead).No amount of flashband or remedial work will cure that .

 

[oldbutnotdead]

That cover flashing looks a bit odd- one end looks like a continuous length sealed with leadmate or similar, the other end has 3 curved bits mortared on...
GRP roof to a parapet wall- there should be a 100mm upstand formed as part of the GRP roof (a pain when it's a pitched roof) 5mm or so away from the wall, then cover flashing goes over the top of it & doesn't need to be sealed to the roof, just chased and sealed into the wall.