Roof Strengthening A frames?

[Mitch]

I have to get retrospective Building Control approval for a roof which has had its slates replaced by heavier tiles. I understand I need to fit an inverted 'A' frame which I want to do my self (to save £350+). Whilst I understand how to make and fit the diagonals of the A frame, to the purlins, I don't have any info on the horizontal beam/s of the A frame (which will link the two purlins) e.g. what diameter bolts/how many/is it two beams or just one? Does anyone have a spec or drawing or could describe it.

Thanks

Si

[jake]

i think you are describing collar ties which are timbers fixed horizontally between the two slopes about half way along the rafter length.this helps to prevent the roof from spreading.four inch screwa are ok for fixing.

if ther are convenient walls or beams available you can also fit a few vertical struts .you can screw them to the rafters but better if you birdmouth to the purlins

jack