UKC

The whole thing is about 3.8m long and 2.4m wide (length of an 8' sheet of ply). The roof is about 1m long on inside wall and the whole thing just under 2.3m tall. There light grey bit (one at each side of the structure) is a 50cm tall bit of ply to add a bit of strength/interest/somewhere to hang finger board etc.

The climbing surfaces will be about 2.6m x 2.4m (steep) 2.2m x 2.4m (shallow) and  1m x 2.4m (ceiling).

The frame is largely 2x6 and 2x4. The interior ply is 18mm phenol impregnated ply and the outer surface is 12mm - I'm only really planning to climb on the shallower outside 'slab' wall. Interior angles are 15 and 40 degrees. The ply isn't cheap, but should be mostly weatherproof but I could throw a tarp over if need be.

I'm planning to put one of the mini moonboard hold sets on the steep side and the kickboard is 15cm to match the mini moonboard.
I'm also torn between tee nuts or no...if doing the nuts I think I'll go for 200cm x 100cm spacing (again to match the moonboard spacing). I have no experience setting but have been climbing a couple of years so I thought nuts would be a good idea as they'd allow be to play with hold positions easily, albeit at some cost.

The three images show the frame, the frame with the internal ply and the whole thing

This is probably the main thing I would be concerned about.

My external wall had a corrugated roof on it to keep the bulk of the rain off it. I used marine ply, and an epoxy varnish to seal all the ends of the ply. I then painted all surfaces (including the ends) with multiple layers of waterproof external floor paint to really seal them all up.

They still blew by the 2nd/3rd winter.

Maybe the ply you are using is better.

I think you need either a diagonal brace or this grey board bit needs to be full height. I can see the screws on this grey board snapping when you are on the 45 degree wall and the whole lot falling over without some lateral restraint. 

The boards will provide plenty of lateral restraint in the other direction.

I was happy with T nuts

One last thing, unless it's a fun and comfortable place to be, if you are anything like me, you won't use it. Winter, nah, maybe tomorrow. Months soon go by.

this is what I built.

The frame is solid. Doesn't move at all. It's the ply that's the weak point, and you can see some of the damage if you look at the photo.

Why restrict yourself. 45 degree wall should be your target steepness

Instead of a tarp which will collect water and hold moisture against the ply roof I suggest you use felt roofing. That isn't perfect but as its stuck to the roof there will be less opportunity to hold dampness. Its the roofing material of choice for pretty much all sheds.

I'd wall in the sides too as  rain is often falling horizontally in my garden - perhaps yours is more sheltered. You could also heat it in winter then

Will you actually use it?

You don't need 2x6, it's overkill.

Extend the roof out over the steeper board and slope it, this can then be triangulated down to the base of the steep wall so it doesn't all collapse on you and it can carry a proper roof.

I'd probably build it quite differently but if this design is what you want, that's how I'd tweak it.

Jk

I think that if you only climb on the outside bit, it's too small.  Two moves and you're up.  Whereas on the inside surfaces, you can swop from side to side, continually.

I'd go down to your local bouldering wall and spend an hour on a similar sized boulder.  See how it keeps your interest.

Dave

Ahh, my bad, what I meant was the only bit of the outside I'd use is the shallow slab, the interior is definitely where I'll be spending most of my time!

That looks cool. What did you do in terms of the ply - which and what treatment? Other people seem to struggle with the ply deteriorating within a year or two

It's 18mm marine-grade ply. I've painted it twice with Ronseal Fence preservative. This is it after 7 years in 2020. I should replace the triangle panels as they are in poor condition now, but the actual wall is going strong.