Mr Blobby Posted October 25, 2023 Share Posted October 25, 2023 (edited) Today's decision is whether to use traditional sarking board or ply under the standing seam. Buildup is : standing seam - membrane - ply/sarking - battened ventilation gap - membrane - rafters - insulation. 35 degree pitch. Sarking board will be timber with 3mm gap between. Laid horizontally on vertical batten. Builder tells me the real timber sarking will last longer than ply. Cost is about the same. I guess its easier to leave the sarking up in the rain during the build without damage so cynic inside me suspects this is guiding builder's recomendation. Timber sarking or ply? Which one's best? Edited October 25, 2023 by Mr Blobby Link to comment Share on other sites More sharing options...
Kelvin Posted October 25, 2023 Share Posted October 25, 2023 What does the manufacturer of the standing seam product you are using recommend? We went with 18mm wbp (class 2 I think it’s now called) plywood as it was what the joiner recommended and, more importantly, the standing seam roofers recommended. You need to fit a vapour membrane over whatever you use so the rain is irrelevant. It was quick to do so it meant we got the roof weather tight really quickly. We’ve barely had a drop of rain in the building since we started. Link to comment Share on other sites More sharing options...
SimonD Posted October 25, 2023 Share Posted October 25, 2023 46 minutes ago, Mr Blobby said: Timber sarking or ply? Which one's best? Sarking is the best and the preferred option as specified by the Federation of Traditional Metal Roofing Contractors. For several reasons including better pull out resistance for the fixings. Plywood is acceptable and tends to be 'preferred' by the installers as it's cheaper and quicker to install and is certainly an acceptable solution. With some it's even okay to use osb.... so in order of best to worst: 1. sarking 2.plywood 3. osb (but don't use osb if you need high pull out resistance for screws or alternatively you need to reduce fixing spacing around both the perimeter and rest of roof area - this needs to be calculated). 1 1 Link to comment Share on other sites More sharing options...
saveasteading Posted October 25, 2023 Share Posted October 25, 2023 Our original building had traditional sarking. If it hadn't, I think it would have rotted and collapsed completely, long ago. The gaps between boards make such a difference in letting water drip through and air movement dry the timber again. All repairs were done the same way. With breather where we could bug without if it was local patching. Where we had to replace the structure we used osb, based on price, and that it shouldn't get wet for some decades, with a metal roof, air gap then breather. Traditional sarking would perhaps have been the very long term decision. 1 Link to comment Share on other sites More sharing options...
Mr Blobby Posted October 25, 2023 Author Share Posted October 25, 2023 (edited) 3 hours ago, Kelvin said: What does the manufacturer of the standing seam product you are using recommend? The standing seam installer said that ply is ok, and he would get membrane on site to cover the ply immediately to protect it from any rain before the standing seam is installed on top. That would rely of course on my roofers working in dry weather and covering as they go. The standing seam supplier did say, however, that if it was his roof then he would use sarking board. Thank you all for your comments. Very helpful and reassuing. Timber sarking board is now ordered 👍 Edited October 25, 2023 by Mr Blobby Link to comment Share on other sites More sharing options...
Carrerahill Posted October 25, 2023 Share Posted October 25, 2023 I would go sarking, make sure it is decent stuff, I have had some crappy circa 15mm stuff delivered and it was very knotty and scary to walk on! Finally got a delivery of decent 22x150mm. Link to comment Share on other sites More sharing options...
saveasteading Posted October 25, 2023 Share Posted October 25, 2023 What gap is specified. I've heard 3 'experts' say wildly different numbers. Link to comment Share on other sites More sharing options...
Mr Blobby Posted October 25, 2023 Author Share Posted October 25, 2023 (edited) 15 minutes ago, Carrerahill said: I would go sarking, make sure it is decent stuff, I have had some crappy circa 15mm stuff delivered and it was very knotty and scary to walk on! Finally got a delivery of decent 22x150mm. My builder likes to talk in old money (which seems common over here) so its 6 by 1. When pushed he did translate to 22 by 150 which sounds lilke the decent stuff you used, which is good. 13 minutes ago, saveasteading said: What gap is specified. I've heard 3 'experts' say wildly different numbers. The roofer said the gap is one nail. They place a nail between the boards as a spacer and thats about 3 mm 😆 Edited October 25, 2023 by Mr Blobby 1 Link to comment Share on other sites More sharing options...
Carrerahill Posted October 25, 2023 Share Posted October 25, 2023 (edited) 13 minutes ago, saveasteading said: What gap is specified. I've heard 3 'experts' say wildly different numbers. Depends on the board, wet, install it tight, dried out, a nail width. Most of it is bloody soaking! Edited October 25, 2023 by Carrerahill Link to comment Share on other sites More sharing options...
Kelvin Posted October 25, 2023 Share Posted October 25, 2023 20 minutes ago, Mr Blobby said: The standing seam installer said that ply is ok, and he would get membrane on site to cover the ply immediately to protect it from any rain before the standing seam is installed on top. That would rely of course on my roofers working in dry weather and covering as they go. The standing seam supplier did say, however, that if it was his roof then he would use sarking board. Thank you all for your comments. Very helpful and reassuing. Timber sarking board is now ordered 👍 Fortunately ours was done in the long period of dry weather we had in May/June. Since then would have been a pia given the non-stop rain in my part of Scotland Link to comment Share on other sites More sharing options...
saveasteading Posted October 25, 2023 Share Posted October 25, 2023 14 minutes ago, Carrerahill said: Most of it is bloody soaking! You mran straight from the tanalising process? That is naughty. At least there isn't cyanide in the recipe any longer, but its still not nice....thats the whole point of it. Link to comment Share on other sites More sharing options...
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