Sarking boards on roof with built in solar trays

[DannyT]

The house is currently going through planning for changes from the original design. In the meantime I’m trying to get my head around the Scottish way of doing a few things.

 

Standard traditional roof construction from what I understand is as follows,

 

Truss

Sarking boards

Breathable membrane 

Slate

 

Now if I’m having built in GSE solar trays, my understanding is we will have to do following,

 

Truss 

Sarking boards

Breathable membrane 

Counter batten 

Tile batten

Slate

 

Is this correct? It’s okay to have the membrane flat with no slack or would membrane go on top of counter batten and be droopy?

Trying to create a thin verge without any facia so looking how to achieve this on the gable ends.

 

cheers

 

[JohnMo]

Effectively completely ignore the GSE instructions, they are not applicable to a sarking board roof.

 

Attach the trays direct to the sarking, through the membrane

[DannyT]

@JohnMo

Thankyou. It’s so hard to find pictures of an install onto sarking and you have provided. Much appreciated👍

That looks very tidy indeed.

Is that a swallow/swift box on the gable?

 

 

[JohnMo]

58 minutes ago, DannyT said:

Is that a swallow/swift box on the gable

No it's an MVHR combined inlet and outlet 

[DannyT]

I’m assuming the membrane will be air and vapour permeable to allow vapour out and air in to flow between the gaps in the sarking board?

Thats a different membrane to the standard “breathable” type and more than likely expensive.

Sorry if gone off topic a bit but just thinking out loud 😁

[JohnMo]

Mine is Proctor Roofshield

 

Standard blurb

The Roofshield breathable membrane is unique due to its patented melt blown core and its three layer nonwoven spun bonded polypropylene construction. It has been designed for use as a pitched roof underlay that is fixed beneath the slates and tiles.

 

The Proctor Roofshield breathable membrane will provide you with a secondary barrier to wind, rain, and snow. It is successfully able to eliminate the incidence of inner condensation in pitched roofs due its air permeability and low vapour resistance.

 

If you’re looking for the most cost effective solution to controlling condensation in a pitched roof, then look no further than the Roofshield breathable membrane. This is currently the only product on the market that can offer you all of the following:

 

Air permeability

Doesn’t need an additional vapour control layer

Hydrophobically treated

Low vapour resistance

Supplied in rolls of 1 m x 50 m

UV resistance

Water resistance

 

 

[Lears]

Just jumping on this as in the exact same scenario. My assumption was I would need to battern on top of the sarking vertically and the counter batten horizontally on that to enable water run off down the membrane that sits on top of the sarking board. Then trays and slates would be fixed to that horizontal batten.  
 

Are you saying you are not counter battening and if so, is that not an issue for water run off as it would get stuck and pool?

 

maybe I’ve missed the point

[Nickfromwales]

On 13/01/2026 at 13:48, DannyT said:

Is this correct? It’s okay to have the membrane flat with no slack or would membrane go on top of counter batten and be droopy?

If you go for the terrible "droopy" option, I'm coming up there and there will be trouble "NO!".

 

Whoever dreamt that idea up?

 

Just done one project where it’s was sarking > membrane > counter batten > roofing batten. That is the way, and the light.  

 

 

[Nickfromwales]

If fitting in roof, remember to have additional battens ready on site for the PV installers to utilise. 
 

They need to be stacked where the fixings on the trays are. See this for an example of a job we did, so you know what is needed   
 

[G and J]

39 minutes ago, Nickfromwales said:

sarking > membrane > counter batten > roofing batten

Then slate.   With solar pv in roof. 

That’s what we’ve done. 
 

Things to note:

 

Ventilated ridge and airflow at the bottom of the slates help the membrane shift water vapour and hopefully cool the panels too. 
 

Most roofers round here will counterbatten but then run the felt directly under the bottom tile, stifling all airflow.  Not good. Close supervision was needed in our case and we had a brilliant and well respected roofer. 
 

Not all membranes are spec’d for this configuration.  Make sure you’ve got one that is. 

[Nickfromwales]

1 minute ago, G and J said:

Not all membranes are spec’d for this configuration.  Make sure you’ve got one that is. 

I should have added this. Thanks!

[Gone West]

9 hours ago, Nickfromwales said:

See this for an example of a job we did

Out of interest, are they NuLok tiles?

[Nickfromwales]

32 minutes ago, Gone West said:

Out of interest, are they NuLok tiles?

Slates. Very expensive ones iirc!!