How much did your extension go over budget?

[Grobagsforever]

I've been quoted 82k for a small back and side extension, two stories. Will create a new bedroom and large open plan dining area. Roughly 30 m square in total. I'm allowing another 15k for kitchen and bathroom purchase. How much more over can I expect to go? Some friends are saying 30 percent, which feels a lot!!

Remember to include all fittings in budget - radiators, kitchen handles, floor fitting costs ( we used a floor company) takeaways (if doing a kitchen) cost of sorting out garden when builders have left!

We went 10-15k over

£15k for a new kitchen and bathroom doesn’t look a lot (assuming £10k for kitchen, £5k for bath). I can’t speak for the bathroom but we’ve recently had fitted in a new room a large painted shaker kitchen with quartz worktops and it’s come in a lot more than £10k. And that’s in the north.

A friend has just has a smaller high st kitchen fitted which came in at £12k for the kitchen only.

Once you add in extras like flooring it creeps up fast!

Thanks! I'm not too worried about going over budget on fittings as that is controllable (there's always IKEA if money gets tight!) bathrooms only cost 1k for materials. It's the builders costs escalating that worries me.

Atleast 20%

Mine was a self build house and that went 50% over but most of that was on things that shouldn't arise for an extension as a lot was to do with getting services to the plot (Electricity was 13k over estimate), other unforeseeable things related to the plot and the main building was interrupted by 'the beast from the east'.

So long as you tie the builder down tight and ensure that his quote covers everything, including any specific materials you require then you should come in close to budget.

One thing that does cause huge additional expense is when you change your mind about things once the job is already started you need to be very sure where the plumbing needs to be and all electric points, lighting etc.

20 to 30% contingency is always suggested but, you really shouldn't need to use much of it if the builder has quoted properly.

Thank you all for responses so far. I could cope with 30 percent but anymore seems unreasonable. I'm not going to change my mind, the design doesn't really have an wiggle room anyway!