Another roof design...

[ollypenrice]

Although this roof is simply designed to make a pavilion over our outdoor kitchen it would also work nicely, I think, for a roll off.  All our roll offs are single pitch but I quite regret not having tried an apex roof along these lines because you get the high part in the middle where it's useful over the scope.

Having only a small MIG welder I have to work in small section tubing, in the case, as in the observatories, 20MM sqaure. By using two runs well separated, though, this produces something you can happily walk about on. (Thanks also to the MIG experts who recently explained why my machine was not working well. It needed more cool down time, simple as that.)

The top of the roof is clad in 1mm flat galvanised steel. We are exposed to high winds on occasion and steel stays put. I like it! It also lasts in the fierce sunlight. However, you can't bolt the flat stuff down without it buckling, so my idea here was to use three sheets which go from one gutter end, over the apex, to fall short of the opposite gutter. On the opposite side a short strip tucks under the first sheets to fill in the gap. The only bolts through the sheets are along the gutter edges, so they can expand and contract as they like. The wooden batons holding them down are also bolted only at the gutter edges so they are, in effect, just straps under which the steel can move. So far, no buckling!

It's proved to be strong and light, so would be a nice system for a moving version.

Olly

[JamesF]

A steel-framed roof isn't something I'd considered before.  I may well give it more thought.

James

[ollypenrice]

It's what I've usually used, though the big robotic shed designed by Per, and one of my small ones, use timber frames.

This is a typical example and has proved reliable. I'm glad the house has had a new roof as well since I was building this observatory!

Olly

[JamesF]

I've been thinking about a pitched timber-framed roof using scissor trusses or triangular gussets inside the apex to give the maximum possible height in the middle of the observatory, but using a steel frame looks as though it would be considerably lighter.  That in turn may well make motorisation and automation easier as well as allowing the moving section to extend down the sides slightly as in your photo above.  Definitely looks like a good plan.

James

[ollypenrice]

I've used both steel and timber with the upper sides moving as well. Both have been fine. My instinct is for steel, though, since timber in motion may develop flexibility in the joints. Part of my liking for steel comes from the fact that I can cut it myself at the builders' merchants over here. I take a cutting list and a tape measure and use their radial arm cutting grinder for which there's no charge. This means I come back with a roof in kit form, all to length and with square ends. Brilliant. 

I then make a simple jig for the component sections, knocking nails into a board to align the tubes for welding. So simple and quick. Indeed it was this speed that got my welder overheating because I could move from joint to joint without having to move any of the tubes.

Olly