Alternative to counter batten on sarkin roof?

[happyolly]

We're building a lean-too shed approx 4.5m long by 3.5m wide.
The pitch is very shallow, about 11degrees.
We're using Forticrete Centurion tiles which work to 10 degrees.
Due to some mix ups between the planning (or lack of it) and work being shared between 3 people (never doing it like that again) we don't really have space vertically for counter battens on the sarkin (boarded) roof.

The slot for the lead is cut in the wall and even it weren't the tiles can't go any higher otherwise the verges will hit the verge of the roof on the wall it's butting up against.

So, the question is - what do we do? Notch the battens maybe? They're laying in 12mm ply which is well raftered and noggined.

Other ideas?

Thanks

 

[catlad]

Well I would cut some strips of lead fold it in two and stick it under the baton as you are nailing it down, that way you will get a couple of mm clearance for drainage or you could buy plastic packers from screw fix.

 

[Alastairreid]

Dispense with the sarking boards and the need for counter battens

 

[happyolly]

Well I would cut some strips of lead fold it in two and stick it under the baton as you are nailing it down, that way you will get a couple of mm clearance for drainage or you could buy plastic packers from screw fix.

Can I kill two birds with one stone here I wonder?
Is there something I can place between the batten and felt where I nail that will lift it up and waterproof the hole too?

Will a couple of mill do it do you reckon? I've been reading the 6mm is recommended minimum.

 

[happyolly]

Dispense with the sarking boards and the need for counter battens

The boards are required at this low pitch to support the felt and prevent ponding. I've spoken to the manufacturer of the tiles and they've said leaving that out is a no-no.

We don't need 12mm though, it's only to support a bit of felt, I don't know why that thick a board was purchased.

Maybe I can return the 12mm and get 9mm OSB and then use 6mm counter battens. I'll ask. All that niggling over 3mm though!

Further suggestions appreciated in the meantime.
Thanks

 

[catlad]

The only other suggestion I can think of is find someone who knows what they are doing.

 

[happyolly]

The only other suggestion I can think of is find someone who knows what they are doing.

We are where we are with this build. Rafters are up, sarking board fixed, roof-felt on. We're not going to entertain the cost of reversing what's been done based on the probably slim chance of it causing issues.

I am hoping to find someone who knows what they're doing ....on here. Just need a bit of advice, that's all. It's a DIY forum I thought?

We're going for the notched battons option. They're drying out in the kitchen now. Substantial routing session begins tomorrow.

Thanks

 

[freddiemercurystwin]

9mm battens? You think Forticrete won't tell you that 9mm battens are unsuitable too? Jeez, sounds like the lot needs redoing or it will just cost more in the long term. Or use a different roof finish other than tiles. Expect to see you in a couple of years how to fix it.

 

[happyolly]

9mm battens? You think Forticrete won't tell you that 9mm battens are unsuitable too? Jeez, sounds like the lot needs redoing or it will just cost more in the long term. Or use a different roof finish other than tiles. Expect to see you in a couple of years how to fix it.

Um, who mentioned 9mm battens?

The battens are 25mm*50mm I think (could be 45mm) and sit firmly on well supported 12mm ply. More than enough, by a long chalk. Confirmed by Forticrete tech support a few days ago.

 

[freddiemercurystwin]

then use 6mm counter battens.

My mistake you said 6mm! Even worse!

 

[happyolly]

then use 6mm counter battens.

My mistake you said 6mm! Even worse!

I read somewhere on the net that 6mm gap was sufficient to let any water that may get past the tiles escape down the pitch.

When you think about the volume of water, which should be none if I understand things correctly, then even 6mm sounds ample.

Do you recommend 25mm for the counter battens (not laths)? Curious why so deep?

Thanks

 

[catlad]

Change the batons for 19x38mm and then you pack them up using lead strips.

 

[happyolly]

Change the batons for 19x38mm and then you pack them up using lead strips.

I guess that way the lead is the bit that gets the water rather then the batons.

Would certainly be easier to run the batons through the thickneser (if they ever dry out) than cut out notches.

 

[jonez]

Change the batons for 19x38mm and then you pack them up using lead strips.

I guess that way the lead is the bit that gets the water rather then the batons.

Would certainly be easier to run the batons through the thickneser (if they ever dry out) than cut out notches.

If your roof works, nothing under the tiles will get wet, as you've suggested the main battens just need to be lifted enough that air can flow beneath them so any moisture rising from below can evaporate meaning you don't get trapped condensation.

Catlad's solution is the easiest way to get a low profile - use 19x38mm battens and insert a bit of packing where they're nailed to give them some clearance. Lead folded to give a few mm's standoff would be fine and long-lasting.