Workshop roof #2

[Jimk]

Any insulation going in?

[Jimk]

Warm roof doable if planned for...

[Jimk]

A warmer workshop... You're increasing it anyways...

[bblaukopf]

After stripping the workshop roof (see Mouldy Workshop Roof), I'm pondering options for improving what I put back on it.

Current construction is a half-brick wall with piers, 4.6m x 4.8m. The roof joists are 6x2 at 60cm centres, and are built into the walls with no sign of any restraints (but these can easily be added...). Roof wall is 1 in 40, which after allowing for the self-weight deflection fo the roof will become 1 in 60.

I'd like to build a pitched roof, but I don't think I can without going through planning.... Not impossible in future, but I'm not prepared to wait for it right now. And I'd need to keep the neighbours on side too.

So - does this plan sound reasonable?

Pack out the existing structure with timber running at 90 degrees to the joists. 6x3" at the high end, decreasing in depth as we move down the fall. 3" so they've got more base to sit on. This is my preferred solution, for simplicity. It boosts me up to a 1 in 20 fall. I can run the packing pieces through the table saw with a cheap blade to get them to the correct size.

Cover with 18mm OSB3 8x4 square edge sheets (I know they weigh a ton. I've got help), spaced with a 3mm expansion gap. Fix with Turbo Outdoor PZ 5x70mm at 300mm centers. Or borrow a nailgun. Batten the side edges to stop drips there. Apply 1 layer of underlay + felt. Considering torch on, though I've never used it - plus I'd need a torch and gas. Is it easy to get on with? EDPM also a possibility, but concerned about application in low temperatures.

[harry]

[bblaukopf]

Looked at that stuff but it wants 5 degrees or 1 in 11.

[bblaukopf]

Wasn't planning on it initially. Could fit later between the joists.

[bblaukopf]

Can't see what it gets me? And increases height...

[newshound]

I suspect it would work at 1 in 20, but whatever angle I would not just rely on rafters and purlins, I'd put it on top of (say) 12 mm OSB. I rent a stable where similar material (probably steeper than 1 in 11) is sagging and in places cracking and leaking at just over 10 years.

One I built in Wickes own brand is sagging all over the place like a sixteenth century roof after 25 years but still watertight. (To be fair it was rated for 10 years).

As a cheapskate, I like the plastic coated steel panels which come in various thicknesses. Just one example:

Ebay item 131415083347

But I don't believe a word of the tech details, it says galvanized in one place and aluminium in another. The cheapest ones are mild steel, plastic coated both sides, about half a millimetre thick. These certainly work at your pitch. No insulation and noisy in rain, of course.

[bblaukopf]

I discovered the existence of Firrings. Couldn't find much online, but rang up my local Travis Perkins and they sold me 3"-0 at 4.8m for £1/metre. And cut it in half so I could it home. They're only 1 in 64 on their own, but combined with the existing fall, that will get me to 1 in 30 when loaded, which is good enough for me.

[Cynic]

I'd forget the buggering about and use something like this .

[Tim Lamb]

In message [e-mail], Cynic [e-mail] writes

Similar to the ones I use. You use butyl tape to weatherproof the joints and long Tek screws (in the valleys) to secure to your purlins.

One point... you need to create a *drip*. Usually done by shortening the underside at the eaves. I use a *demolition saw* fitted with a metal cutting blade and then scrape off the insulating foam. Not so good on very shallow pitches.