Basement Conversion Advise

[TheWife]

Have a customer with a basement that is exceptionally dry, apart from front wall in one corner, suspect the cavity is blocked. Never embarked on a basement before. Looking for some advise.

Digging down to check depth of foundations tomorrow, in same location as the blocked cavity (will clear this at the same time), Requires an addtional 300mm headroom. Any advise here would be great.

Also, as walls are dry, customer said does not want to tank. What is the bare minimum I should do to these walls prior to battening and plasterboarding.

 

[chappers]

How old is this property.Would be very surprised if this basement has cavity walls.
Check to see that there isn't another reason for the dampness like a leaking gutter, downpipe or incoming water supply etc.
If you are not going to tank the place then there is little point doing anything to the walls before boarding, but I would be very wary of this approach.
What is the location of the property, with regards to the water table say.

 

[TheWife]

Built 1894. Situated in Southsea (Portsmouth, Hampshire).
I have requested that the customer signs as part of our Customer Specifics section of the Terms & Conditions, that he does not want us to tank it. You are right about the cavity.....we dug down and found that there was nothing....arrrr...what should be done in this case if we require additional headroom.

 

[chappers]

you will need do dig out what you need but with a victorian house like that there won't be any foundations as such it will be built on top of 3 or four courses of corbelled foundations. you will basically have to underpin the house this involves digging down in 1 meter sections under the existing walls laying in foundations and blocking back up under the existing foundations. then doing the next meter.
Then relaying a new floor slab.
you will need a structural engineer and building regs approval.
They will want you to dig a series of test holes to confirm the foundations.

 

[TheWife]

OK, any idea on how much money we are talking to underpin?


MOD

please see item 9

 

[TheWife]

There appears to be what looks like a lot of flint rocks below. I spoke with the customer and he said that the house opposite was built same time and they did not underpin when the dug out there basement.