Corrugated galvanised steel roof - insulation?

[Keith 66]

Re drilling concrete panels as Brad sez the back just blows out if you get through at all. Near the edges the panels usually have steel rods & hit one you are stuffed. But many will already have precast holes in & you can pick them up & use them. This is what i did with my recent roof job, the wall plate was offered up alongside & holes marked. I drilled them a bit oversize to allow for a bit of misalignment. Counterbore on top & used 8mm studding to bolt them down. All bedded on Polysulphide goop. They wont be coming off again.
Other stuff that will bond them is Polyurethane sealant or Gripfill.

 

[tigdlo]

What's the OSB for?

That's a good question. I put it on mine to add to the structure and to provide a flat surface so there was no chance of pooling as the pitch is quite a low angle.

 

[julianf]

A lot of different ideas above. Thanks to all.

How about this for a plan -

Thin batterns on top of the steel a frames, running parallel to the ridge (ie horizontal)

The a frames are about 1m30 apart btw

150mm on top of the a frames (and batterns) running vertical (perpendicular to the ridge)

Cellotex between these, supported by the first set of thin batterns.

Then membrane. The cellotex is 120, and 6" timber c16 is, what, about 145ish? So about an inch difference, which will allow the membrane to sag under the next set of horizontal batterns and allow any run off.

Then some more, what, 2x1 (?) batterns and then the sheets fixed to these.

Do I need more than 2x1 for the last set? Seems slim. Again, distance between the a frames is about 1.3m iirc.

(The one above the main door is not fitted in the photo, as I still need to weld up the frame)

 

[gaz1]

mines a wide garage similar to yours about 10 ft back of garage

i choose 2" to go over the walls first as i intended for the next one to be used internally and to go ove a wood frame on the internal side of it

3x2s as they was cheap but gives you something solid to fasten too on both the roof as well as the insulation layer below the wood level

note my timbers use the original roof holes as i havent drilled any more holes in the angle iron

and mine has been up for a few years now

some of the walls has an insulation layer wrapped around

 

[Ton-up]

In about 1988/89 I bought a used concrete double garage with centre wall. I put it up to be a single garage of 28' x 14'.
I made a few simple timber trusses and then covered it all in 5/8" marine plywood that I got really cheap as, so I was told, it had been salvaged from a sunken ship!
I then bought some really thick mineral felt and glued and nailed it on horizontally. I lined inside he walls with battens and thick hardboard.
That garage is still up as I built it 30 years ago, the felt is original, although I think it may need replacing in a few years time.
My point is that I have never had any condensation issues ever. It would be easy to make the roof as I did and then fix your insulation to the underside of the plywood.

 

[Gareth J]

A lot of different ideas above. Thanks to all.

How about this for a plan -

Thin batterns on top of the steel a frames, running parallel to the ridge (ie horizontal)

The a frames are about 1m30 apart btw

150mm on top of the a frames (and batterns) running vertical (perpendicular to the ridge)

Cellotex between these, supported by the first set of thin batterns.

Then membrane. The cellotex is 120, and 6" timber c16 is, what, about 145ish? So about an inch difference, which will allow the membrane to sag under the next set of horizontal batterns and allow any run off.

Then some more, what, 2x1 (?) batterns and then the sheets fixed to these.

Do I need more than 2x1 for the last set? Seems slim. Again, distance between the a frames is about 1.3m iirc.

(The one above the main door is not fitted in the photo, as I still need to weld up the frame)

How will you fix the big, upright 150s through the perpendicular battens below and into the steel a frames?

Don't think I'd want the heaviest beams just hanging onto the first skinny battens personally. Guess you could make up some odd, long, flat cleats.

Alternatively, if going for this method, you could bolt your 150mm beams to one side of your a frames maybe, rather than precariously balancing them on top.

 

[armalites]

A lot of different ideas above. Thanks to all.

How about this for a plan -

Thin batterns on top of the steel a frames, running parallel to the ridge (ie horizontal)

The a frames are about 1m30 apart btw

150mm on top of the a frames (and batterns) running vertical (perpendicular to the ridge)

Cellotex between these, supported by the first set of thin batterns.

Then membrane. The cellotex is 120, and 6" timber c16 is, what, about 145ish? So about an inch difference, which will allow the membrane to sag under the next set of horizontal batterns and allow any run off.

Then some more, what, 2x1 (?) batterns and then the sheets fixed to these.

Do I need more than 2x1 for the last set? Seems slim. Again, distance between the a frames is about 1.3m iirc.

(The one above the main door is not fitted in the photo, as I still need to weld up the frame)

If you fit a ridge board you don't need any battens under the 150x50 rafters and I don't think battens will be of any support unless they are only there to contain the cellotex.

6" rafters are more than man enough, if you look at modern houses it looks like they make the roof trusses out of match sticks, sure they are triangulated but from memory I think 6" will span 3m at 400 centres

 

[julianf]

I'm talking of putting the 6" on top of the metal a frames.

The only reason why they are also on top of the thin (cellotex supporting) batterns is that I can't fix the thin ones to the bottom of the steel without bother.

(If you look at the photo, the steel is angle, so it would be a load more bother to hang the cellotex batterns than to put them on top, under the 6")

 

[Afterimage]

When I fitted a corrugated steel roof to my garage I used a layer of 9mm OSB,then a layer of that silver bubble wrap insulation I got used from Ebay for almost nothing folowed by the corrugated sheets.
I wouldn't want to live in it,but I don't get condensation raining down on me in winter so I call that a win.