another metal roof leak thread

[bigegg]

I put a new roof on my 20x10ft garage over the summer:
it slopes the long way at an angle of about 20:1.

I used good condition, 2nd hand metal sheets with proper roof screws, on new joists above the old (plywood) roof.

it's still leaking!!!

the roof sheets are overlapped about 8 inches, but I didn't use any sort of sealant on the joints.
they are tight, and flat though - no huge gaps.

I'm not sure if I'm getting run back under the joints, or water is getting through the screw holes.

im rhinking of buying a couple of gallons of "black jack" damp proofing paint and putting on a couple of coats to build up to about 3mm thickness, or even some tar and applying it hot?

is this likely to work? or should I take the roof up and seal the joints as well?

waiting until next year isn't an option, so need something that will work now - even if it means using a flame gun to heat up the roof.
obviously I'll pick a dry day!


I haven't added to the other thread, because that's more about bad access and foam.
I have easy access.

 

[cumbriasteve]

Are you sure it's not condensation forming on the underside of the sheets, this time of year is perfect for it and mine produced gallons when the weather was right for it, the garage floor was soaked.

 

[Shox Dr]

20:1 is very shallow. With no sealant used, it could be tracking through capillary action

 

[rockweasel]

Here's a photo of the back edge of my workshop roof.
The sheets are overlapped such that water can't wick up and over the joint.
The screws are through the "peaks" of the roof and not the troughs (the guy who put up my shed years ago did the opposite and I had nothing but leaks).
The screws have a rubber washer to stop any moisture getting through.
I've put enough of an overhangs at the back to stop any water sneaking around the edge, and the back end of the workshop it protected from wind so I felt no need to put any infill . There is foam infill on the front edge.
Barge boards line the sides of the edge to finish them off and stop any water blowing in sideyways.
I put down "Protect" waterproof breathable membrane before the steel went on just in case any water got through.

So far, so good.

 

[Burdekin]

Seal the joints.

 

[Johnrob]

I agree with Steve, either condensation, or is rain blowing in the ends?

I have less pitch than you (approx 1 in 40) some of it has the sealing tape in the overlap joints (approx 6in), some doesn't (ran out of tape).

No leaks.

I know one thing, water cant get through steel sheets, so its either condensation or water is getting round the edges somehow.

You could try the hosepipe trick to locate it perhaps.

I 'king hate leaking roofs!

 

[bigegg]

Are you sure it's not condensation forming on the underside of the sheets, this time of year is perfect for it and mine produced gallons when the weather was right for it, the garage floor was soaked.

it's not condensation, and it's not wind blown. very sheltered area, and it only leaks when it's pouring down.

it's difficult to tell for definite, but it's flowing down the underside of the sheets, so it's a leak.

recommendations for sealing tape? or window/door sealant?
and best way to seal (old) screwholes? sikaflex? frame sealant?

or a 3-4mm full coat of bitumenish stuff?

 

[bigegg]

View attachment 160088 Here's a photo of the back edge of my workshop roof.
The sheets are overlapped such that water can't wick up and over the joint.
The screws are through the "peaks" of the roof and not the troughs (the guy who put up my shed years ago did the opposite and I had nothing but leaks).
The screws have a rubber washer to stop any moisture getting through.
I've put enough of an overhangs at the back to stop any water sneaking around the edge, and the back end of the workshop it protected from wind so I felt no need to put any infill . There is foam infill on the front edge.
Barge boards line the sides of the edge to finish them off and stop any water blowing in sideyways.
I put down "Protect" waterproof breathable membrane before the steel went on just in case any water got through.

So far, so good.

the perimeter has overlaps, and bargeboards.
to the point where it's difficult to see where the rain is coming through.
my screws are in troughs, with sealing washers.
there are holes in troughs from previous fitting, but I fitted the sheets such that they're not "through" holes.

 

[cumbriasteve]

I can vouch for this stuff, not cheap but it works great.

https://www.travisperkins.co.uk/Iko-Pro-Roofcryl-Grey-5kg/p/885758

 

[bigegg]

I can vouch for this stuff, not cheap but it works great.

https://www.travisperkins.co.uk/Iko-Pro-Roofcryl-Grey-5kg/p/885758

thanks.
what sort of coverage will I get with that?
there's nothing on the website, but prefer real life experience to manufacturers guesses anyway

 

[Johnrob]

"there are holes in troughs from previous fitting"

Flashband patches?

 

[armalites]

With box profile the screws are supposed to be in the troughs, if they are done through the peaks they can flex. With corrugated they go through the peaks.

 

[bigegg]

after another look, I'm reasonably certain it's capillary run back up the sheets at the joints, so will seal them all as soon as the weather calms down.

what to use though?

 

[Johnrob]

There is special stuff for that, bit like foam draught excluder tape. You would have to lift the upper sheet a bit to slip it between the upper and lower sheets.

I got mine from Foregales when I bought the sheets.

 

[bigegg]

There is special stuff for that, bit like foam draught excluder tape. You would have to lift the upper sheet a bit to slip it between the upper and lower sheets.

I got mine from Foregales when I bought the sheets.

"butyl sealant tape"


ta

 

[bigegg]

With box profile the screws are supposed to be in the troughs, if they are done through the peaks they can flex. With corrugated they go through the peaks.

yes, fixed through troughs. I pop rivetted sheets together on peaks.(with a blob of sealer before fixing).

I put my back out lifting mum off floor over weekend, so I'm a bit spaced out on painkillers.

 

[Mattuk]

Would low modulus silicone squidged into the gaps between the panels work ?
May be easier that trying to get enough gap to fix tape between the panels

 

[cumbriasteve]

thanks.
what sort of coverage will I get with that?
there's nothing on the website, but prefer real life experience to manufacturers guesses anyway

Not sure but I went along my own joint in a 200mm width 7 metres long and hardly used any of the tin, it's thick and has I think a fibre bonding appearance, I liked it because I was able to press it hard under the joint before finishing it off with a smooth brushed surface.... looked good too.

 

[macandmoss]

when I did it on one of my buildings the lad I know who got me the second hand sheets helped me , he brought a couple of rolls of putty type sticky tape ,a bit like stuff you used to put on under kitchen sinks ,hobs etc but a bit thicker, this was what they used when putting the buildings up so there is proper stuff , he put it on the hill of the last joint before screwing it down ,don't know whether it worked as I plyboarded over the joists and put two layers of visqueen on top of that so if any condensation formed it ran on the visqueen and out the end , always like overkill ...lol

 

[rockweasel]

With box profile the screws are supposed to be in the troughs, if they are done through the peaks they can flex. With corrugated they go through the peaks.

I understand what you are saying, however the installation guide says both trough and pan are acceptable for box section:

(I set the torque on my cordless drill to give a snug fit without distorting the profile)