Is there a particular advantage in putting some sort of membrane under the cladding ? Neither my workshop nor garage have but I'm extending the garage for general storage purposes and I see that a membrane is mentioned in the DIY handbook I have.
Rob
One house I looked at buying[1], the bloke had built himself a first class workshop. He'd put blue plastic sheet under the exterior panels, insulated with polystyrene then boarded inside.
Advantage: I suppose to guarantee no damp ingress, which would be all the more important if boarding the inside - and less draughts.
Cheers
Tim
The message from "robgraham" contains these words:
My brother used a breathable membrane - nice snug shed, doesn't let the draughts in, but doesn't get damp.
OK - what do I ask for when I go to buy 'breathable membrane'. I do have a further requrement which would justify this as I need to re-clad my workshop, and I'm all for making sure that there are no draughts.
Rob
The message from "robgraham" contains these words:
Have a look for breathable roofing felt.
There are various types of breathable underlay felt. One of the better known is Tyvex but there again there are different types for different applications, Vapfree is another brand. Since the introduction of breather underlay, every felt manufacturer as brought there own out. By far the best is Roofshield, bright green in colour non tearable, and I mean non tearable. A new Stanley blade or sharp scissors are required to cut Roofshield, the other will tear if a sharp cutting blade is not used. Prices range from £60 for the economical ones to £109 for Roofsheild.Un fortunately they all come in 50mtrs rolls. If you only want a few mtrs you might get an off cut from a roofing contractor. Which ever brand you use you must leave an air flow gap between the ship lap boards and the underlay. Lay the underlay first then fix counter battens vertical and fix the ship lap to the counter bitterns. It is not advisable to fix the counter battens horizontal as this will stop any condensation from run out. All fixings should be galvanized coated .
Many thanks Keith - that was a great reply. I'm not that enthusiastic about the money but between the garage extension and the workshop re-face I can probably justify the 50 mtrs. The counter battens give me a slight headache in one area, as I haven't allowed for them - I can probably get away with 12mm - is this enough?
Rob
If you do go for Roofshield, there instructions state " leave a 10mm gap" Thats when used for roof cover, all its for is to stop ponding, Ponding is water vapour condensation from the back of the roof tiles or slates dripping off and not being able to run down the underlay to the eave.If the underlay is pulled tight it touches the back of the battens and stops the trickle causing PONDING. In the case of shiplap dont fix it direct to the underlay if you do you will create PONDING
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