First Frame Up

An Eccentric Anomaly: Ed Davies's Blog

Having put all the available main posts up and marked laser level points on each the next job is to take them down again, drill holes for the joists to bolt on, fit the steel brackets and the tie beams between north/south pairs (across the house) and stand them back up again.

The main purpose of the tie beams is to keep the purlins vertical. They're well supported from below by the posts but the sloping roof would tend to topple them inwards so the tie beams across are pretty beefy: 195 by 45 mm C24 (the stronger of the two commonly used structural timber grades) doubled up and bolted on quite solidly.

As designed the two 45 mm beams go between two tongues on the bracket which are nominally 90 mm apart. What could possibly go wrong?

The obvious one is the timber being slightly oversize but actually it's pretty good - this is not cheap timber and they don't want to give you more than you've paid for.

Second obvious one is the timber cupping which it has but only very slightly.

The position of the tongues on the brackets are pretty good, too (better than the similar tongues on the base brackets). However, the brackets have curled in slightly, presumably as a result of the weld or some interaction between the weld and the galvanizing. First a general view of the bracket with a lump of wood bolted to the back:

then a slightly closer look lined up to show the curve of the bracket:

Doing up those nuts on the bit of wood pulls the bracket straight, particularly with a bit of 18 mm ply stuffed in between to give it some leverage. Those “bolts” are actually M12 threaded rod. As I was packing up at the end of last year's adventures I tried this out but the nuts jumped on the rod. That was because I was using galvanized nuts on BZP rod. Galvanized nuts have a different thread to make room for the galvanizing and don't fit firmly on other materials with the same nominal diameter so I picked up some BZP nuts specifically for this purpose.

With that sorted and a fair amount of hammering some of the brackets go on. For others a bit of sanding of the end of tie beam is also needed.

Fortunately my drill stand can just get in to make the bolt holes:

The frame can then be stood up with the help of a Lidl chain hoist. It's good that I can stand well back and out of the immediate line of likely rope sprong if things go wrong:

Actually, just after I took that photo I dropped it back down enough to be able to get close safely as I remembered to add a back rope to each post to stop it all going over centre.

It's hinged off a gash bolt through the lower bolt hole in the each post and the upper bolt holes in the base brackets. Once it was up and tied off in both directions I dropped it down by alternating blocks on each side of each post:

The hole above the slot is the lower of the two for the joist with the laser level marks on each side.

First frame up and guyed for the weekend's wet and windy weather, second frame ready to go up but a bit scary to try in Friday afternoon's pretty stiff breeze and the remaining posts down and stacked until next week: