Cavity Trays - RetroFit - any idea of costs???

[planestrainsautomobiles]

Unfortunately we have lots of damp and leaks following the storm. We had an independent damp survey undertaken and unfortunately our builders didn't insert cavity trays when we had our extension built 2 years ago.

According to our surveyor we need to have cavity trays inserted and the cavity wall insulation removed from the back of the house where we have water ingress (following the storms over Christmas & New Year). The back of our house is west facing and suffered with the driving rain and severe winds.

Has anyone had cavity trays fitted after an extension was built, if so, what type of cost are we looking at, it sounds like a huge job? TIA.

[ASET]

Hi
I know this was a while back but I have the same problem now. Did the cavity tray work? & did the builder admit liability?
Thanks!