I am buying a new house and it will have a 10 yr nhbc warranty , my question is if i fitted a conservatory my self do i invalidate my warranty, the sales staff say i would i dont agree anybody got any experience about this ?
I've never heard of this John, but, knowing the NHBC, I wouldn't be surprised.
As you're in the process of buying, ask your solicitor to examine the NHBC insurance closely - he should anyway.
The NHBC is merely a warranty - 2 yrs on components that might go wrong like CH pumps, 10 yrs on structural failure. One wouldn't expect what you are proposing to impact on it, but NHBC has got itself an incredibly bad name for finding allegedly spurious reasons to deny the validity of a claim. For this reason I suggest you write to them and get a reply before you decide to do this.
The sales staff of the developers are nothing to do with the NHBC - don't take their word for it - they want the sale.