10.02.2021 New boundary post mock-up.

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 Wednesday 10th. 27F. Snow still here but the wind has finally dropped. I was quite comfortable working outside in a fleece jacket.

I decided to do a mock-up with 2x4s [Metric 50x100mm] of the upright posts of the larger building footprint. There was a lot of packing and clamping involved while balancing ladders on the edge of the gravel pad. Until all the posts were more, or less, upright. Each post is resting on the metalwork jutting from its foundation block. Not an easy thing to photograph and still get all the posts into the picture.

Some of the posts would pass right though the present veranda. Requiring shorter posts to fit underneath just for this mock-up. I had no desire to start searching for the veranda fixing screws just to remove the necessary boards. Not under the hard frozen snow!

In the real construction the posts would reach right up to the roller supporting, building's, top ring. The mock-up posts were just what I had available from the intended, dome transport trolley. I'd need 4.2m posts for the real thing.

There are a lot of joists under the veranda. Making any likely ladder repositioning a bit of a chainsaw massacre. I'll look at that issue again when the new building is properly outlined.

Seeing the posts in place suggested a change in earlier panel building decisions. Now I am thinking 2x4 main posts arranged 'flat' [tangential] to the circumference of the new building. 

The plywood cladding panels could be edged with regulation [metric] roofing battens. [Probably 38x57mm] For lighter handling [than the full 2x4s] but still of very adequate strength. Two x 57mm almost matches the width of 50x100mm [2x4] posts for the panels to fit neatly together edge to edge. These panel edge battens would increase the [100x] 50mm deep posts to 87mm in depth.

If I wanted much more strength I could screw a 2x4 to the back of the first set of 2x4 posts. Either laid flat for 100mm overall + panel edge battens. [138mm depth.] Or, set on edge for a 100x150mm 'T' profile. [188mm total depth] 

The latter arrangement would provide greater beam depth for improved structural stiffness. [Due to the increased moment.] I have not bevelled the panel, edge battens in the drawing. [Above right.] I think I prefer the upper arrangement in the image [above right] as being more than adequate.

The interior angles of a multi-sided polygons become relaxed when there are so many sides. I am assuming 15 sides. 12 new + 2 existing but with the latter at wider spacing. So I added a fictional one. 

So: [n-2] x 180/n = [13x180]/15 = 156°. Using 14 sides in the formula results in 154°. An almost trivial difference.

 

The 100mm faces of the posts would be bevelled to half width. The joining faces of the panel, edge battens, also bevelled on the table saw.

I would add diagonal 2x4 braces internally between the upright posts. For a very sturdy perimeter structure. This would require compound mitres. Appropriately spaced, horizontal braces, of 2x4, could provide shelves. Or provide solid support for deeper shelves.

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