Roof dishing problems...

9 Jun 2009
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United Kingdom

I'm in the process of buying a back-to-back terraced house in Yorkshire, and have received the surveyors report in the last few days.

The biggest concern is that there is some dishing to the roof, which the surveyor beleives has been caused by the original slate tiles being replaced by concrete tiles. At the moment the cause is not certain as the roof space is converted into a bedroom with dormer, so it's not possible without invasive work to find out what strenthening (if any) was done when the tiles were changed.

Assuming that this is the cause, and the roof needs strengthening, how would this be done? And how much would it approximately cost? Obviously it's only "half" a roof, but I'm concerned the cost could be prohibitive!

Thanks in anticipation of help!

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With loft conversion, the rafters can sag as the timbers are knocked out, and before the supports put back in. So the roof ends up with a permanent dip.

If there were inadequate supports, then it would be a bit obvious shortly after the work was completed. You don't have to rip the roof apart to see this

Check all the b/regs permissions are in place, and if so ask the surveyor to confirm if there is any current distress with the roof, other than a dip.
many roofs built for slates will suffer from roof sag if they are replaced with heavier concrete tiles. The roof should have had some strengthening work done before it was re-tiled. Best to get a more comprehensive check on this just to make all is ok
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Hi Daniel,

Assuming worse case scenario - the roof hasn't been strengthened - how would this be best rectified?

Thanks for your help,


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