Wall frame options

[RikM]

Well I've started scribbling ideas for my obsy but I am not sure which way to go for the wall frames. Most small/mid sizes don't seem to have cross-bracing. Is there any real advantage to a cross-braced design in a 3mx2m size?

The outer cladding will be either 12 or 16mm redwood shiplap (depending on overall cost). I would like to line the inside with some form of sheeting board but I don't know yet.

Which frame would be better?

[teleskopjo]

Well B is inherently more rigid, I would go that way!

[Psychobilly]

Digz (Lee) is your man....

Ply lining will really strength up the frame....

Peter...

[yesyes]

I was planning on using diagonal bracing on my obsy. I wanted to add them later when I know how much timber I had left. But in the end everything was so rigid that I did not add it at all.

One other thing though...

If you are going to line the inside with some sheet material, make sure your uprights are at the right spacing. The vertical join of 2 sheets should be on an upright. I didn't think of that when I started building and had to add a few uprights later just for the sheet joins.

[callump]

I would actually go for A - because, when the roof rolls off, there will be a lot of weight resting on the mid-point of the bearer, with no support at all, so dependent on the strength of the wood there. 

I actually clad mine in exterior OSB - cheap and does not look too bad painted green. And does lend some structural integrity. 

One other tip - think about how you will change the external roof bearers when they rot. I made the mistake of continuing them into the structure of the 'shed' (to get a nice straight run) so replacing them is a very tricky operation (as they have rotted into the ends of the shed).

Cheers, Callum

[twintin]

Being a joiner I used a combination of A & B. the diagonal bracing offers a massive amount of structural rigidity and for the sake of around £20 it seemed silly to miss them out. Also worth bearing in mind is that the roof won't add to the strength as its not fixed so any additional strength can only be a good thing ( especially with all the wind we are having at the mo)

[r3i]

I went for C , which was a combination of your A & B - i.e., smaller 45 degree bracings, you might just be able to make them out in the photos in this post: http://stargazerslounge.com/topic/168972-yet-another-observatory-build-thread/?p=1719232

They certainly helped keep the structure more rigid during construction, but it was after adding the cladding that everything went really solid.

[Tinker1947]

The frame for B is more rigid unclad, but Frame A will be better if you clad the inside with full size sheets of 12mm OSB screwing this to the uprights and in the cross section centres, this will not all make it really rigid, but you will know where the uprights are so screwing battens ect for shelving will be easy, taking this build on a few years you will also be able  to insert a door if you require another add-on section the B type frame won't lend its self to this sort of alteration......

[JamesF]

If you're cladding with shiplap then I think you must brace diagonally.  If you were cladding with sheets then you might get away without, though personally I'd probably still put a couple of diagonals in per side anyhow because it avoids a large shear load being put on the cladding fixings.

In fact, what I'd probably do with walls as tall as that is put horizontal noggins in at 540mm high, then a diagonal in opposite directions in the end "bays", one above the noggin and one below.  That's pretty much what I did with the childrens' tree house and it is still there despite being quite exposed:

James