Overlaps not taped

[Mr Blobby]

The breather membrane is now in place on our pitched roof.  Roofers haven't taped the overlaps of course.  Is it worth getting it taped now?

 

Roof structure like this:

 

1. Standing seam

2. Membrane (yet to be installed by standing seam company)

3. Sarking boards (to be installed this week)

4. 50mm ventilation gap counter battened (installed)

5. Tyvek supro breather membrane

6. Rafters + Mineral wool between rafters (part installed at eaves)

 

So the vertical laps are ok, they are next to the batten.  The horizontal laps, if blown by the wind will not lift up any tiles because there will be sarking board above.  However, any wind blowing up the ventilation gap from the eaves will blow straight into my insulation, and that can't be good, can it?

 

Is it worth telling my roofers to tape down the horizontal laps between the vertical counter battens as they install the sarking board, or do I just put this down to experience and move on? 

At the two valleys of course, there are a nuber of overlaps.  Maybe this area should be taped even if the rest of the roof isnt?

 

Of course, the taping should have been done before the battens went on but too late for that now.

 

There also appears to be some leaking, which is disappointing.  The end of the rafters at the wall plate are wet.  Water may be getting in at the nail holes, but its not obvious.  The membrane is wet to the touch underneath, but no drips, as if there is condensation or tenting. 

Also, I suspect the membrane may be too tight without sufficient dip beteween the rafters but this is not helped by full-fill insulation limiting the sag. 

 

If I could turn the clock back then I would probably have PIR between the rafters (the springy stuff with Z-cutouts) with a gap above.  And sealing tape for the nail holes.  And taped before battened.  

Every day gives a new lesson in how to build better 🤔

 

Edited November 5, 2023 by Mr Blobby

[Crofter]

I'm a bit confused by your build method. You're using a non tenting breather membrane, but then adding sarking on top anyway?

And why was it necessary to have horizontal joins? Bit late now but wouldn't it have made more sense to run the membrane vertically, and then use the counter battens to pin it down at the joins?

[Mr Blobby]

On 05/11/2023 at 12:53, Crofter said:

You're using a non tenting breather membrane, but then adding sarking on top anyway?

 

The sarking is required for the standing seam.

 

On 05/11/2023 at 12:53, Crofter said:

wouldn't it have made more sense to run the membrane vertically, and then use the counter battens to pin it down at the joins?

 

Good point. Yes it would make absolute sense.  Why didn't I (or my roofers) think of that? 

I guess its because most roofs are tiled and so this is how they always lay the membrane.

[Crofter]

Is there anything on top of the sarking? Just the battens and then the standing seam sheets?

I know this isn't very helpful but it seems a strange way to build a roof. I hope that whatever you're using for sarking is ok with a bit of moisture.

[Mr Blobby]

45 minutes ago, Crofter said:

Is there anything on top of the sarking? Just the battens and then the standing seam sheets?

I know this isn't very helpful but it seems a strange way to build a roof. I hope that whatever you're using for sarking is ok with a bit of moisture.

 

Our roof buildup is like this:

 

 

 

... which is from the good practice guide for metal roofiing (FTMRC).  The standing seam company have understandably requested same buildup from our roofers.

Instead of using ply on top of the battens we are usaing timber sarking board, but this came from the metal roofers as they think it is a better option than ply.

The sarkng looks great, almost a shame to cover it up.  Like this:

 

 

I have been told that the membrane that will go between the sarking and the standing seam will be waterproof.  Not just a debonding layer.  I hope so because right now storm Debi is pulling those un-taped laps away from the nail holes 😫

 

 

 

 

Edited November 13, 2023 by Mr Blobby

[Crofter]

Ah ok so there's a second membrane to protect the sarking.

 

I did a corrugated steel roof but only used one membrane. I wonder why standing seam is different.

[MikeGrahamT21]

This may help decipher what you should have got: https://www.labc.co.uk/news/understand-bs-5534-changes-roof-underlay

[Mr Blobby]

39 minutes ago, MikeGrahamT21 said:

This may help decipher what you should have got: https://www.labc.co.uk/news/understand-bs-5534-changes-roof-underlay

 

Interesting how that link says the laps should be taped.  That peice of good practice is news to the roofers around here.

 

My breather membrane (Tyvek supro) is labelled as all-zones so is ok in theory but if I was choosing a membrane again I would look at something a bit stronger like solitex plus.  Our membrane, where exposed and not taped, is going to be getting a good battering in this storm today 😫

 

Edited November 13, 2023 by Mr Blobby

[MikeGrahamT21]

Yeah almost no one knows about this guidance, ive observed many roofs being constructed over recent years and not one had any tape in sight.

 

Tyvek Supro is a premium brand, but i agree, there is far better out there, its also one of the least breathable of breather membranes.