No additional purlins were installed, however, I did make progress on fixing down over the steel walling for the existing purlins

After talking to Tony M I realised that tekscrewing the Z purlins down to the steel wall framing was not going to be enough.

Over the PFC and U beams we had good, substantial, welded 6mm cleats that did an excellent job of holding the purlins rigid. However, a couple of tekscrews over the steel framing would allow them to flex too much.

The supplier of the purlins believed that a couple of tekscrews would be quite sufficient.

Even Patrick, the structural engineer believed that after the floorboards were screwed on the structure would be sufficiently rigid - however, he said that if I was concerned about it I could install cleats over the steel framing walls and insert standard bridging across the longest spans.

Considering that two stories of building are to go on top of this deck, I decided to play safe and install "Handy C cleats" from Midalia Steel - these are 1.5mm thick, 75mm wide, 75mm high, with a flute for rigidity.

If you look at the image of the Handy C Cleat you will see that they have a large number of predrilled holes and are obviously meant to be fixed from above - however, when tekscrewing down in to the 1.2mm steel framing - there is not enough "meat" for a secure fastening (it strips out the thread in the steel framing) - so I was forced to drill two of the fixing holes (diagonally opposite) out to 12 mm to take galvanised bolts on to the steel framing.

Then, if I Tekscrewed from the cleat in to the purlin, through the vertical face of the cleat - this gave a good solid fastening

Finally, I drilled down through the bottom leg of the Z purlin in to the steel framing and pushed Tek Screws up from below, through the steel framing in to the 1.5 mm purlins to achieve a good fastening.

There is still a little bit of flexing going on - but much more solid than before.

The frustration came about because I needed to retrofit the cleats to 7 of the exisitng installed purlins, over two steel framing walls - this involved undoing some existing bolting and bending the purlins back about 100 mm to give access to bolt down the cleats.

It was important to retrofit the cleats, and also install them at all other positions, before installing any more purlins

What also added to the work, was the fact that I had previously pop riveted down galvanised steel plate packers at a few locations and these needed to be moved about 50mm to lie under the cleats.

I should have rung Tony M and put him off to another week as this job was not appropriate for him -(he has a bad ankle making it difficult to work from above the purlins - though normally he is fine working off a rolling scaffold to fix the purlins to the cleats) So in the end we just got in each other's way and I was much less efficient than if I had just worked on my own.

He was disappointed and frustrated that he couldn't get on with the main job that he was best suited to, and I was frustrated that I did not make more progress that day

Ah well - I guess you live and learn (-: