Clad a pre-fabricated

Hi All,
Just moved to a new house where there is a pre-fab concrete garage. I wanted to make it into a playroom for the kids so will be getting a new roof ( current one is corrugated with gaps where it meets the walls). Anyway, wanted to clad the outside with wood and insulate and board up the inside. Any ideas how I would do this? I was going to drill through the walls and bolt batten to both sides allowing cladding and plasterboard (and insulation) to be screwed to the batten. I have attached a drawing. Thanks for any advice in advance.

First point :- there will be some form of steel reinforcing within the panels, this cannot be drilled, so must be avoided. I would work out the drilling pattern so its the same from panel to panel, so hopefully when you avoid the steel in your first panel, you will avoid all of it. So you have worked out your pattern, try it out on one panel and amend it if required.
If you through bolt, you will need to counter bore both inside and outside battens so the bolt head and nuts are below the surface of the wood. The counter bore will have to be wide enough so you can get a socket onto the head for tightening it.
I would be tempted to use 6mm stainless steel studding cut up with a nut and washer at each end, strong enough and cheaper then long bolts. To save counter boring the battens it could be an idea to cut up 12 X 1" X 1/8" ali angle into 3" lengths and drill one face for your 6mm stud and the other for 2 off 4.5mm holes for screws to go in to the sides of the batten. So the battens lay slightly to the side of the studs. This means that you have a 100% clear wood surface to use for your plasterboard or external cladding.
frank

That number of bolts is impractical, and you will have nothing left of those panels after all those holes.

You probably need to devise something with two or three timbers fixed to the garage with fixings at 600 centres, and then the cladding and board fixed to those.

Hi prince and woody,
Thanks for your replies. Prince, did you mean 3 inches or 3 feet? I was going to bolt 3 feet apart top to bottom with 18 inch centres.
Also, any ideas about the roof and floor? I was going to install a better roof( cost more than the garage I know) to insulate it better and need a floor. Seems to be on a solid concrete base.
pic attached. The floor slopes down under the decking so the garage is about 10" higher. Don't really want to raise the floor much due to the doors. Thanks again in advance

Ah a Marley garage?. I reckon 3 or 4 fixings in the total height is enough. I meant 3 inches of ali angle, just enough to get the 6mm stud fixed through one face and a couple of screws through the side into the wood. I had another thought , you could use flat "tabs" of metal. Again 3 " square, screw them to the BACK of your battens so 1" sticks out the side. This is where your stud will go through it. Trouble with this method you have to be accurate with your holes , else you have to to take a batten off to move a tab or re-drill the holes.
To avoid splash back terminate your external cladding 6" above the ground and paint the panels black with some bitumous paint - see what others say about this, as some bitumous paint goes white with the sun.
For the floor a lightweight floor would be 22mm P5 T&G chipboard laying on 1"/2" of Celotex. Just don't put a grand piano on it.
Your roof, the difficult thing is to seal the eaves properly. Foam filler is only so good, because of the slope of the roof it squeezes out eventually, perhaps use some sooper glue, like Stix All? The main problem with the roof will be condensation dripping off the underneath of it. The only theoretical way to cure this is to bond insulation to the underside of it so there is no air gap. I am not sure that glass fibre is airtight enough for this. The only other thing to do is to vent the under roof area and use a plastic sheet to protect the insulation that will be lower then it. Bearing in mind you might actually need a small drain to get rid of a pint or two of water.
Frank

Just re-read your first post. There is a good roofing material that is made by Corus. its two sheet of steel separated by 3" of foam. Its what the big sheds use for their roofs. Both outsides are covered in PVC, the underside is white, the top is available in all sort of colours ( B&Q red. . .) and textures. It is available at a surplus place, but I have lost my references to the place, they also do a wide range of corrugated iron roofing, so wind up Google and spend the night looking for it.
Frank

You can fix your battens though that mastic joint without drilling the panels

Hi all,
Thanks for all the replies. Looking forward to getting started. I will look into the 22mm P5 T&G chipboard laying on 1"/2" of Celotex. It will just be the kids toys and luckily they haven't asked for a grand piano yet.
I will also look into doing the roof, probably overkill but this is London and it all adds value.

I was thinking of using mastic to hold the battens but worried about not being able to support anything on the walls.
Cheers everyone

oh and I might change the garage doors for a patio door.

Hi all,

5 years late to the party but if anyone comes across this post, wondering how to clad their pre-fab garage, I've done a blog post about how I clad ours. Hope it's of some use!

https://project-number-nine.com/2020/08/26/cladding-a-concrete-panel-garage/

Jack