Lean to garden office

vail3r

vail3r

vail3r

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I'm helping a friend put together a Lean to Garden Office against the back of his garage. We have poured the base and a few courses of brick for it to sit on.

My understanding of the correct wait to construct is:

4x2 for frame
18mm OSB on outside and covered in breathable membrane
treated battens over membrane before cladding
vapour barrier and plasterboard on the inside

We will then be planning on using the light weight plastic tiles for the roof and insulating with 100mm PIR which will leave a 50mm+ air gap above the insulation

Is there anything I'm missing or should be doing different?
 
I would have as much insulation as you can. Floor and garage wall as well. Makes for a much nicer working space.

How about a velux?
 
Lean said:
I would have as much insulation as you can. Floor and garage wall as well. Makes for a much nicer working space.

How about a velux?
Click to expand...

We have talked about adding a Velux or 2, but he is on a budget!

Good point about the garage wall, I'd not thought of that.
 
200sols said:
No need to OSB the outside simply clad directly to the frame using the membrane in between.
Click to expand...

Why not? Most garden room builds I've seen all seem to clad the outside, I assumed this was just how it was done.

Is it just to add rigidity to the frame?
 
vail3r said:
Why not? Most garden room builds I've seen all seem to clad the outside, I assumed this was just how it was done.

Is it just to add rigidity to the frame?
Click to expand...
I've built several garden offices and summerhouses, never used OSB once. If you want spend the extra money saved on thicker cladding, loglap is nice.
 
alexakasloth said:
How would you go about the rest of the construction of the walls?
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I'd clad the outside leaving one from the top, cut the roof rafters with birdmouth cuts and then clad up. You can then fit the roof and begin to work on the inside. Joist thickness Will determine how much insulation you can fit in but in my experience these rooms heat up and retain heat well with surprisingly little. My own garden office was the first one I built with just 25mm polystyrene. I think with 4x2 joists I'd go with 75mm boards these days, bare in mind most quoted 4x2 are planned off and are actually only 95mm deep so this ensures an air gap. Then I clad the inside, I like t+g pine boards, for me plasterboard doesn't suit a garden room but each to their own. If the roof is pitched in the middle you can make a nice feature of the supporting timbers if that is your thing but shallow pitched roof work just as well and easier to install.

Of course, you also have companies like Tuin who have a really nice solution to off the shelf builds using much thicker timbers which can negate the need to insulate the walls at all.
 
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