Anyone seen this sarking board before?

[Dave-K]

Hi guys. I'm looking to convert my loft space and have noticed a few of the sarking boards are sagging in places. The boards look like compressible fibre filler boards. Certainly not standard softwood sarking used in Scotland.

Anyone seen this used before for this purpose? I'd rather proper sarking was there but really don't want to to strip the entire roof to do a loft conversion.

Cheers

Dave

 

[^woody^]

I've seen it on several types of system builds in England from the 60's and 70's, and yes it does sag.

 

[KenGMac]

Dave-K, good evening.

The material is a soft board called Cellotex, it was used as a direct [poor] replacement for Sarking.
Used as an alternative to Sarking by Local Authorities and Spec Builders, the material was widely used in the 60s and early 70s.

Downside of the material is it burns nicely, and as you have found deforms having no strength, it can be squeezed back and held in place by some small timber battens nailed to the joist sides, also the material will deteriorate massively if the rain penetrates the tiles and felt [if there is any felt in place]

Ken.

 

[datarebal]

great for pin boards..

 

[Westmarcher]

I know this is an old topic but I am now experiencing this issue also. I wonder how Dave-K got on. My house was built in 1984. My pal, a retired civil engineer, identified this as Celotex also, but when I contacted Celotex, thinking they must have experience of this issue, they were a bit cagey saying they weren't sure that this was their product - even though I had sent a link to this topic to them and mentioned my pal separately identifying it. Having said that, their most experienced guy (who I spoke to) only has 14 years service. His solution was to take the roof off and replace(!) - not really the route I wish to go down.

So, what to do? Well, for me, I think I'll try tackling the problem in two phases. First, I'll try to support the undamaged and least sagging ones before they start to sag and fall out. Then, secondly, put my thinking cap on again and try to come up with a solution to replace the ones which are basically write-offs. For "Phase 1," KenGMac's reply was very helpful but I'm not exactly sure how the battens should be attached. I had previously tried attaching a simple strip of wood to 'increase' the width of the rafter but I'm not sure how effective that is because the board is still sagging. Maybe I never pushed the board in back far enough (not straightforward, or even possible, with some of the boards) or perhaps the batten wasn't thick enough. So my next idea was to try to install some kind of support that will give both lateral and longitudinal support.

I have now installed a dozen diagonal wooden support battens to see how this works. This unfortunately involved a bit of preparation - cutting the ends at an angle and tailor fitting each support to fit between each pair of rafters (the gaps are not uniform) - but the actual installation was relatively easy. The two end off-cuts were then nailed to each rafter (usually only one nail but hole pre-drilled to prevent splitting) and then the support batten was slid in. By the way, I drilled another hole in the lower support block and inserted a wooden dowel to stop the diagonal support slipping down. Unfortunately, I don't know how to post photographs so hope this description is adequate.

It's quite an elegant looking solution and, so far, reasonably inexpensive. However, I've only tried this on the higher parts of the roof. The lower parts where it meets the walls will be a nightmare because of the restricted access. Has anyone else done anything on this since 2016 and what did you do? Also, what about those panels that are beyond fixing? Any ideas about replacing these?

 

[^woody^]

identified this as Celotex

"Celotex" (one L) is a silver foil-backed insulation board, and nothing like the OP's photo.

 

[Westmarcher]

Thanks, Woody. I had considered the spelling issue and, having looked at Celotex's website, appreciated that the current product is foil backed as you say. I think the current Celotex Limited was incorporated in 1987 (according to Companies House) - 3 years after my house was built. But it was the only lead I had so I had to pursue that. It was strange, however, that two people with experience going back further than that both separately thought this was "Celotex" or "Cellotex." If the other sources are correct, perhaps it is a product name (and not the manufacturer's name a way back in the 60's, 70's and 80's). Unfortunately, whatever the sarking board is, I still need to come up with a solution. Cheers.

 

[Makie]

"Celotex" (one L) is a silver foil-backed insulation board, and nothing like the OP's photo.

You get old Celotex boards that look like this, they were used often in Scotland.

 

[KenGMac]

That material is indeed Celotex, I recall using it on local Authorities new builds [back in the day] 45 / 50 years ago.

I still see it in vast volumes when undertaking surveys in loft spaces.

A soft board, fibrous and prone to deformation over time especially when damp, will collapse if wet,

Now for the real kicker it is very Flammable [burns really well] On site at lunchtime in the dead of winter we used to get of-cuts, sit on the ground floor joists with the Celotex burning in the fire place, at temperatures getting near to Zero [back in the day] ???

Was used as "Makie" above all over Scotland, indeed i did a survey on a fire damaged roof [the adjacent property went up] the sarking in the roof I was inspecting was made of Celotex, that survey was last week?

Ken.

 

[paralucent]

Apologies for bringing this thread back from the dead (again).

I too have several loose, hanging Celotex boards in exactly the same condition as the OP's (see the second photo in post #1). I'm interested in using support battens to prop them up but I don't know which battens to use or where to buy them. Please advise.

 

[DiyNutJob]

Apologies for bringing this thread back from the dead (again).

I too have several loose, hanging Celotex boards in exactly the same condition as the OP's (see the second photo in post #1). I'm interested in using support battens to prop them up but I don't know which battens to use or where to buy them. Please advise.

For the interior, you can use any wood you like. Wickes, B&Q etc all have a timber section.

 

[paralucent]

Thanks. So 'support battens' basically means bits of wood hammered into the rafters rather than a specific product.

 

[DiyNutJob]

I am sure you can use specialised products. I am no roofer, so I know nothing about them. The cheapest option is to use the simplest method of holding them up with a piece of wood. If those panels are light weight, then use thinner and cheaper wood.

Pro roofers here like to say I am wrong, so you can wait for their response as well. They may well give you something elaborate and suggest hiring pro roofers.

If you are going to do it yourself. Be careful with the hammer. You don't want to knock things out of shape. I'd just use screws to minimize hammering.

 

[paralucent]

I am no roofer either.

I'm not clear how large or wide the battens would need to be. As Westmarcher explained above, raising them up will not stop them sagging in the middle.

 

[DiyNutJob]

If those panels are somewhat stiff, nothing to stop you adding a piece of wood parallel to the rafter. Then the panel can rest its edge on that.