Roofing Specification states Tyvek builder has used Ti-R Classic membrane

[Winston]

Hi

We are looking for some advice.

We just checked on our loft extension work to find TI-r classic has been used as the membrane for or roof and dormer walls. Tyvek has a density of 125 and the thinner membrane he has used is 100gsm (zone 1-2) only). Its an Edwardian semi in London. They are not the same quality membranes.

he roofing membrane is fairly tight but we have cross battens.

Currently we have a 50mm gap underneath the membrane  to the insulation.

We were paying top wack for the roof and had specified Tyvek in our JCT contract.

Our concern is not just the few hundred pounds difference in price pocketed by the builder.. ....But the repercussions of a poor membrane in a few years down the line if the membrane fails which could mean stripping and reroofing.

We are also worried about a draughty loft conversion which we had on another property when less dense membrane was used, and the membrane degrading.

.

Anyone any experience of not getting what they specified? And what to do about it, if we ask him to strip the roof, the builder and still has the extension to go, and he likes to find extras.

 

Also are there any other cute short cuts we need to look out for.

We also found every 5th course was nailed with 1 nail only.

The roof tiles are now on in a record 2 days.