How much for extra foundations?

[Beckyt80]

We have just started our extension and have come across our first hiccup. When the foundations of the side extension were dug we noticed the width looked a bit narrow. It turned out they were 50cm too narrow. Luckily the concrete hadn’t been poured at this point. When we looked at the plans we realised that there was a mistake as it said 2275 when it should have said 2775 (drawing was to correct scale ... it was literally a typo as the 1st floor dimension was correct). So, the builder had to increase the width of the foundation by 50cm along an 11m stretch. This obviously meant more labour cost, more waste to be removed and more concrete required. We have today recieved a bill for £890 + vat for this. I have no idea if that is a fair price..... does anyone have an idea? It’s such a pain.... eating into our contingency in week 2!!!

That sounds reasonable to me. We are in a similar position as knew that the garage foundations were unknown so only test holes would determine the plan of action and therefore be an additional cost to our build. A week in and we had to pybto getbour foundations reinforced for our over garage extension. With labour and materials we’re looking at around £1500+ although waiting for the actual bill.

Who prepared the plans? Can you ask to split the cost with them as it was their error?

It sounds reasonable but I would also be taking it up with the person who did the plans. Would it have been obvious to the builder it was wrong? Some builders don't really pay enough attention to the plans they are building from 🙄