looking to add a basement on my new build costs pitfalls exp

[newbie29]

Hi all thanks for looking

im looking to add a basement onto my new basement ive got the planning for a 120sqm basement, has anyone been through the process cost involved pitfall money saving ideas.

the new build will be built up against my existing house so underpinning will be required, was originally going down the water proof concrete route, however it seems far to risky, have now decided to go down the safer tested method internal tanking with pumps.

at one point was considering splitting the contracts and jobs into the following stages to save money 1) underpinning original house from a underpinning specialist......2) excavation hire a man with digger.......3) get a formwork specialist construct and carryout concrete pour.....4) tanking specialist to tank basement structure, everyone have talked to has advised well against it as alot can go wrong, i have building experience but never gone under ground.....Does anyone have a idea of the costs for a basement shell with tanking, as internal fit out i can do.

Any help would be much appreciated...cheers Max

 

[jeds]

I would strongly advise employing one contractor to complete all of the structural and waterproofing works. If you use different contractors with no central contract it will be almost impossible to resolve any problems that arise later.