Corrugated steel fixings for steel-purlin garage

[Brigadier]

Help appreciated.

I have a concrete sectional garage, with steel roof frame. Cement sheet roof is well past its best, so I have bought corrugated steel sheets to replace it with.

It came with hook bolts, but the mouths of the hooks are too narrow to hook around the steel frame purlins.

So I am considering self-drilling (rubber-washered) screws.

Good or bad idea?

Screw through crowns, or troughs? (I've seen both methods advised).

I was thinking of putting treated 1" x 1 1/2" timber strips between the purlins and roof sheets, to keep the two metals separate, and delay rusting through.

Thanks in anticipation.

 

[noseall]

Wouldn't you be better off fixing a timber to the steel purlins then fix your sheets into this? You could set it slightly higher to avoid metal - metal contact if you so wish.

I like the sound of using pre-washered tek screws. Made for the job. Fix 'em to the peaks.

Mind you aren't tek screws made for flat profile?

You may need to buy the dedicated dome washer thingys with the curved washer and cap, specifically for corrugated sheets.

 

[alan333]

AFAIR you bolt through the peaks if it's a roof (horizontal), and to the troughs if it's a wall (vertical).

 

[Brigadier]

Thanks Noseall - how easily do tek-type screws cut through the (3-4mm, mild steel) purlins? (I dread the thought of the wind ripping the sheets and fixings out of the timber..........)

 

[noseall]

Thanks Noseall - how easily do tek-type screws cut through the (3-4mm, mild steel) purlins? (I dread the thought of the wind ripping the sheets and fixings out of the timber..........)

Not sure to be honest.

I use a lot of self drilling screws and these are an absolute boon.

I guess as long as you have a decent torque driver then the hex headed beasts should drive in ok.

My thoughts are that they are designed for thin sheet material. It may just be a case of a small pilot hole with a decent HSS bit, just to get you started.

 

[drewroof]

hi, tek screws will go throuugh a mild steel purlin like a hot knife through butter,
if you are using a corrigated profile you fix through the crown, using a stand off tek, if your using a box profile you fix through the trough,using 25-30mm zed teks with stitchers every 450mm on the side laps,and would use foam fillers to suit the profile of the sheet on the eaves and ridge also i would use a 9x3 mm butyl sealant tape on the laps and side lap. theres a firm near me which will sell you everything you need.