Anyone used Sarking board under standing seam roof.

[gavztheouch]

Im about to start building my ventilated deck. I prefer to handle sarking board vs large sheets of 18mm plywood. I noticed Vmzinc say you can use sarking board under their Zinc. Just wanted to know if anyone has used this method. How did it go? Are there any disadvantages?

 

Some advantages I can think of are.

 

1. increased ventilation behind the Zinc.

2. About half the cost of Marine plywood, the best ply option, Still slightly cheaper than acceptable plywood.

3. No risk of delaminating

4. May be more forgiving if your 600mm rafter centres are not perfect. You could cut the wood back to the next rafter. Im not sure about this one.

5. Easier to see rafters to nail.

6. May be possible to do the job myself or with a little help from my dad.

 

Disadavantages.

 

1. Wood thickness may vary a lot board to board.

2. The boards ends may split easier than ply

3. Less coverage per board and potentially more cutting/measuring

4. Badly warped/cupped boards may need to be discarded. Some boards may warp on the roof. Do I need to double nail each joist to stop them coming up as they dry?

Edited 8 hours ago by gavztheouch

[Iceverge]

I think @Patrick did this. 

 

I'm not a fan of standing seam straight down on top of ply. It gives nowhere for the water to dry to if it gets in there.

 

Normal sarking boards might not be the ultimate option either. As there'll be a membrane on top of them, you risk making a moisture trap between the membrane and the sarking. This isn't a issue with slates as there's plenty of air gaps between them. 

 

I would do something like. 

 

Standing seam, 

 

Closely spaced sarking boards but not touching,

 

Counter batten along the line of the rafters to create ventilation gap. 

 

Roof membrane,

 

Rafters. 

[Iceverge]

For what it's worth though I wouldn't do standing seam at all and would just use normal profiled sheeting. 

 

@saveasteading had some professional experience of this being a better option. 

[Russell griffiths]

 

I did this. 

[gavztheouch]

37 minutes ago, Iceverge said:

I think @Patrick did this. 

 

I'm not a fan of standing seam straight down on top of ply. It gives nowhere for the water to dry to if it gets in there.

 

Normal sarking boards might not be the ultimate option either. As there'll be a membrane on top of them, you risk making a moisture trap between the membrane and the sarking. This isn't a issue with slates as there's plenty of air gaps between them. 

 

I would do something like. 

 

Standing seam, 

 

Closely spaced sarking boards but not touching,

 

Counter batten along the line of the rafters to create ventilation gap. 

 

Roof membrane,

 

Rafters. 

 

Thanks, this is what I had in mind about. I did have an additional membrane over the sarking boards but I see how this is not helping. Vmzinc have a detail for this and they do not have a membrane over their sarking board but they do over the plywood. I agree I would not use standing seam again. My biggest dislike is the hard to repair factor. I have 4 flat roof dormer windows that will no doubt leak at some point, could be a nightmare waiting to happen

 

 

[gavztheouch]

26 minutes ago, Russell griffiths said:

 

I did this. 

This makes a lot of sense. Wish I had a nice simple roof with no dormers.

[saveasteading]

The point of metal cladding is that it spans between supports.

So you could have battens at quite a distance, according to the product.

 

The cladding should not leak but might get condensation under it, hence this void /ventilation idea is sound.

 

I'm not against standing seam as such, and the risk of leaks through screw fixings is removed.

Why did I never use it?

horrible to repair if ever a branch damages a panel etc.

The flat bit is very flimsy  and does not tolerate cutting for services.

Why choose a no-screws product and then screw through it?

Cost

I gave every client the choice. In most cases they had been told it was best and not told anything else...including the cost.

 

sarking in solid board, even osb

then a breather membrane so it never gets wet

battens up the slope, 

battens across the slope

cladding.

 

 

[Iceverge]

1 hour ago, saveasteading said:

battens up the slope, 

battens across the slope

 

I'm stealing this. 

 

It makes a way more sense than "battens/ counterbattens"