Building extension - Breather membrane leaking

[jimjones235]

We're in the process of building an extension - I'm doing some parts myself but getting in trades to do the parts I don't have the skill or knowledge to undertake (which so far seems like quite a lot!).

The roofers came and batten and membraned the roof last week and installed several roof windows at the weekend. I'm guessing it should be weather tight now, but the water is pouring in through the membrane. It looks like the biggest areas of issue are the plastic eaves guards, and where the battens are nailed to the rafters (water is getting stuck behind the batten, then pooling and finding it's way through the nail holes). I think the plastic eaves guards are causing an issue as they don't let the membrane sag so the water pools and finds the easiest entry point - which is the nail holes. I guess my question is, should I be worried about this? I realise that the tiles should take most the weather, but as we're using concrete plain tiles (which are min pitch 35 degrees, which is how the extension was design but the roof is actually at 34 degrees due to a few measurements not quite working out) then I'm guessing the I want the membrane to be doing it's job. I should point out that we're having some very very heavy rain today so maybe it's exceptional.

 

[xdave]

I am not a professional roofer but when I did my self-build extension roof I cross battened to avoid just that problem. i.e. membrane over the rafters, vertical battens on top of the rafters and membrane and then the horizontal battens as normal. That prevented the water from sitting on the battens and inevitably coming through the nail holes. It also prevented the tile securing nails from penetrating the membrane if they were too long. I don't know if that is a generally acceptable practise but I discussed it with my BCO he seemed happy with either using the vertical battens or leaving them out.

The reason I did this was because being a self build I wanted the building water tight so I could work inside after dark. Although it is only meant as a backup measure I thought it was better to have it more reliable than less for the sake of a few £ worth of extra battens. Research at the time showed that many people build roofs using both methods so I don't think either is necessarily right or wrong, but I would be interested in your answers from some of the professional roofers on here.

At the eaves I folded the end under a couple of times to prevent it sagging (about six inches of underlap) and stuck a nail in each rafter just above the eaves guards which I just slid in underneath. I didn't want to nail through the guards in case they ever needed to be replaced, but I live in an area sheltered from high winds.

 

[noseall]

The roof tiles are your primary weathering fabric.

If these leak, panic.

 

[^woody^]

I disagree.

The felt or membrane should be a waterproof layer, and especially so with interlocking concrete tiles.

There should be no ponding or sagging at the eaves either

 

[catlad]

I will tell you why its leaking in, its because they have pulled the membrane to tight, and if your roof is going to be tiled with plain tiles then plastic eaves trays are not normally compatible.

 

[noseall]

I disagree.

The felt or membrane should be a waterproof layer

With what, i did not say that the membrane should leak.

and if your roof is going to be tiled with plain tiles then plastic eaves trays are not normally compatible.

Tell me about it.

 

[^woody^]

]With what, i did not say that the membrane should leak.

.

Not in so many words, but you seemed to imply that the tiles keep the weather out and if they leak then panic

Q. How does any householder know if the tiles are leaking?

A. When it pours through the membrane

Except for driven rain between the laps, any sarking should keep water out

The tiles and sarking membrane are a system, there is no primary as each is as necessary are the other

 

[noseall]

So why bother with tiles at all then? They may as well colour fix the membrane with a tile pattern and be done

What about all those poor folks who don't have a secondary membrane?

Think your talking pants Woodbine.

 

[^woody^]

A membrane is required for interlocking concrete tiles. That is what I said

As you know, clay tiles and slate don't let any water through so don't need a secondary layer

A membrane with a tiled pattern? Hmmm, like felt shingles you mean then?

Now I know how F1 engineers feel

 

[noseall]

A membrane full of batten nail holes to boot.

F1 engineers are far to sensitive for diy-not.