New fibre cement roof - wet patches underneath

[Max M]

New fibre cement roof installed a few weeks ago.

In this heavy rain I’m seeing wet patches on the underside of some sections (some on edges, but some just in the middle of the sheet as you can see in the pic of a ridge section), and then around most screw holes there are wet patches after rain.

New building, new roof (and expensive!), didn’t expect this.

Is this normal? Any thoughts or suggestions?

 

[will_mck]

The nail hole photo, is the proper fixing used? I'll take a photo of our fixings tomorrow, it's like a sealed rubber boot under the screw nail. Your nail hole looks to be letting water which shouldn't be.

The ridge caps look wet, on new fibre cement manufacturers will say when the sheets are new there is a thing called 'a curing process' where the sheets are still drying out after the manufacturing process. Sheets may look like that for 6 weeks I've been told but after that they should look and be dry once they've cured.

The last photo, have you allowed enough overlap on the sheets?it can be 150mm or 300mm depending on the pitch of the roof to stop rain blowing back up, some use tape as well for this purpose. It could be an issue regarding how the sheets are notched.

It's hard to say without getting an independent expert, I'd ask the advice from another experienced shed erector who's worked alot with fibre cement as they'd have a good feel for what's wrong.

Finally are your sheets Cembrit/swisspearl in a completely unrelated note?lol

There's no reason in the world why your roof shouldn't be dry if all things are as they should be which is what you would expect. Don't let anyone tell you different

 

[Max M]

The nail hole photo, is the proper fixing used? I'll take a photo of our fixings tomorrow, it's like a sealed rubber boot under the screw nail. Your nail hole looks to be letting water which shouldn't be.

The ridge caps look wet, on new fibre cement manufacturers will say when the sheets are new there is a thing called 'a curing process' where the sheets are still drying out after the manufacturing process. Sheets may look like that for 6 weeks I've been told but after that they should look and be dry once they've cured.

The last photo, have you allowed enough overlap on the sheets?it can be 150mm or 300mm depending on the pitch of the roof to stop rain blowing back up, some use tape as well for this purpose. It could be an issue regarding how the sheets are notched.

It's hard to say without getting an independent expert, I'd ask the advice from another experienced shed erector who's worked alot with fibre cement as they'd have a good feel for what's wrong.

Finally are your sheets Cembrit/swisspearl in a completely unrelated note?lol

There's no reason in the world why your roof shouldn't be dry if all things are as they should be which is what you would expect. Don't let anyone tell you less

Thanks for the reply, I’d appreciate a photo of your fixings tomorrow so I can compare them to the ones that were used here. A lot of the fitting holes are letting water in.

I’ll check the overlap tomorrow to see what it is, and thanks for the reassurance that the ridge wet areas might just be in this curing process window.

It’s Briarwood sheets.

 

[Max M]

Should say, it was professionally fitted

 

[will_mck]

Here's my new nails. There's a plastic cap you can get to fit on top of the head, I always fit them too as I believe it helps run the rain off the screw heads. These screw shouldn't be tightened too tight either as you need to allow a little for expansion when the roof heats up.

I don't think your issue is with the manufacturer at this stage unless those ridge caps never dry out. We always fitted a cranked ridge cap on every ridge cap to improve ventilation but it's not really necessary.

It's hard to judge what exactly is wrong in each photo apart from the nail hole issue without being there to see it but if you know of another good shed erector who's worked alot with fibre cement they're your best bet for an opinion. It may not be the fault of your roof fitter either as he is a professional as you say. You'll want to know where the problems lie though regardless

 

[grainboy]

Pins possibly put in too tight, distorts the seal, or not tight enough, seal not sealing,
Damp patches will appear on un cured fresh sheets, but will eventually cure and dry,

 

[Max M]

Here's my new nails. There's a plastic cap you can get to fit on top of the head, I always fit them too as I believe it helps run the rain off the screw heads. These screw shouldn't be tightened too tight either as you need to allow a little for expansion when the roof heats up.

I don't think your issue is with the manufacturer at this stage unless those ridge caps never dry out. We always fitted a cranked ridge cap on every ridge cap to improve ventilation but it's not really necessary.

It's hard to judge what exactly is wrong in each photo apart from the nail hole issue without being there to see it but if you know of another good shed erector who's worked alot with fibre cement they're your best bet for an opinion. It may not be the fault of your roof fitter either as he is a professional as you say. You'll want to know where the problems lie though regardless

This is what is here. It does look the same as the ones you’re showing me.
But it looks like it might need tightening, I can see the rubber boot is gapping slightly, perhaps they need is tightening a little.

 

[will_mck]

I'd have a go at tightening them slightly, grainboy would be more of a expert than me. As he said you'll just want to turn enough seal the rubber but not squash it flat so the rubber fails

 

[steveR]

Reminds me a bit of something I was told by an experienced roofer when I built my first house back in the early 90s, with an Eternit 3" corrugated sheeting roof.

At the time we were using twist nails with a sealing washer as per normal, but as we were working on a shallow 15 degree roof pitch, he recommended a dab of mastic sealant from a mastic gun under each washer before the nail was driven home. As other have said said, the washer was compressed very slightly when the fixing was put in properly.

Screw fixings should allow a bit more control these days in fitting them.

 

[Badshot]

Definitely don't overtighten them, it can, and will crack the sheets over time.
Seen it done on a whole roof.

 

[matthew]

Pins possibly put in too tight, distorts the seal, or not tight enough, seal not sealing,
Damp patches will appear on un cured fresh sheets, but will eventually cure and dry,

Maybe.
We had this problem, several years ago, and it turned out to be a manufacturer's problem with the mix of fibre v. cement.

An 'expert' came out and told us exactly what you've just said. Very arrogant. So I replied that i'd pay for only the steel, but the roof would be settled, 'eventually' and only when it had 'cured and dried'.

Fortunately the erectors were sympathetic, and replaced all the sheets.

The suppliers went bust. The sheets were Russian in origin (from memory)

 

[grainboy]

I’m no expert as normally just removing them,,
But in doing so see many of the problems,
Have replaced some with a mate, who is a very good roofer, can only say it’s a nightmare of a job especially on replacement jobs,
Purlins including concrete ones sag, it’s then a job to get every sheet sitting right,

 

[grainboy]

Uncured sheets, for what ever reason, seem to absorb moisture,

 

[Lincsman]

New fibre cement roof installed a few weeks ago.

In this heavy rain I’m seeing wet patches on the underside of some sections (some on edges, but some just in the middle of the sheet as you can see in the pic of a ridge section), and then around most screw holes there are wet patches after rain.

New building, new roof (and expensive!), didn’t expect this.

Is this normal? Any thoughts or suggestions?

Back in 1984 when my store was new mine did that, mainly the ridge ones, a year later they were fine and still are.

Mine are secured by those big nails and a plastic washer BTW