Strengthening a roof (was slate now concrete)

[spooky_b329]

I am selling my house, our original survey said the roof would need strengthening due to the original slate being replaced with concrete tiles quite some time ago.

Nothing to worry about, we were told, easy to do DIY. Seeing as the ridge is straight and no sign of sagging we just left it for five years, but now we are selling, what would be involved just to keep it from cropping up again in the buyers survey?

Its a mid terrace house, quite a small roof.

The ridge is just under 12' long. Rafters are 4x2, joists are 4x2 and approx 23' long, approx 15" c2c, purlin on one side is 4x3 and the other is 6x2, I think the bigger one is a replacement. The purlins are approx 4' from the joists.

Am I correct in thinking I just need to add some uprights to support the purlins mid span? If so, what size should I be looking at and I guess I would need a span across the ceiling joists to prevent the ceiling downstairs from sagging?

Or, on the other hand, if it comes up in a survey is there a chance it would be checked and they would say its OK seeing as it has been there years with no signs of problems?!

Thanks guys

 

[palaceray]

Normaly they ask for 3 collars to tie the opposite roof slopes together. This would typicaly be 4x2 timbers fixed into opposite rafters tight underneath the purlin.

Also three Jacks per purlin. Typicaly 4x2 fixed at right angles under the purlin and on to a surporting internal wall. Jacks fied next to collars and bolted to them with a dog washer between.