This house has 10 windows, all replaced 3 years ago with uPVC windows. On a 20 year old breeze block part, the rendering is cracking, so is inside plaster work. On the old stone bit there is no cracking. The insurance surveyor says that the metal lintels which were built for the wooden windows are not strong enough for the weaker uPVC frames, so are sagging. So, in other words, house insurance wont pay up (the small print problem). Window company's insurance might take the opposite view! Has anyone heard of lintels sagging because of a change from old wood to new uPVC? Watching the installers levering in the new with crowbars etc, could that have triggered the cracking in the weaker (new) part of the house? Id be very grateful for any other examples and views.