My initial (naieve) reaction was that this would have an effect of raising the price of new builds by 5%. This doesn't seem too bad - it might make new development more viable, while giving FTBs a slight advantage over existing property owners. Then I realized that making this 5% part of the deposit has got a multiplier effect, allowing FTBs to access much more credit (if their LTI permits it). Can somebody check my maths here please? Before these rules, an FTB with 30k cash could buy a property priced at 260k. Now an FTB with 30k cash can mortgage a new build priced @ 346k?