Building a Cellar before I add my extension Information, help and advice on many architecture, self build and design problems and issues

[grant01]

Hello, nice site by the way.

My dilemma:

I’m looking to build an extension on the rear of my property and I would like to add a cellar to the build so that I can maximise on square footage.

I don’t have an existing cellar; it would be a completely new build, plenty of room for a digger. I am trying to get some information on how best to do it, i.e. block work or concrete poured into a blanked off space, which is better/safer.???
The area in question is 6000 x 3000 mm.

Does anyone have any tips for me or recommendations? Or should I just get in the specialists and bite the bullit.

Thanks in advance.

[andysarah]

HI, as a structural engineer I design a lot of this type of project, I would not attempt this if you are not a competent builder, get a specialist in, I would say building rooms below ground brings with it a lot of technical problems which the layman may not initially spot.
Regards Andy

[kbrownie]

Hi, I too am wanting to build a room beneath a new extension again to maximize square footage. I do already have cellar, so as I understand it they have to dig down that far anyway. So seems logical to have a room there. But still wait for planning for extension. It would be nice [u][b]andysarah[/b][/u] if you could give me a little information in what would be involved in this type of project. I do not intend to do this work myself already have builders giving quotes.
Cheers
KB

[andysarah]

hi,
what is your builder basing his quote on?

the main problems revolve around ground water, high water tables, purched water tables, ensuring the room stays dry, getting a second means of escape and ventilation. all very specific to individual properties and there location/geology.

what form of construction is being proposed for the retaining of the soil against the new basement?

where are you based? i am in the south east of the uk
rgeards
andy

[LCL]

ANDY - KSI?

[kbrownie]

Hi andysarah,
Still in early stages, planning not yet been granted. But builders being sounded out. Can't give you any detailed info because once planning confirmed then get building controls in and engineers calcs.
Sorry only elbowed in, to see if anybody had helpfull info on what work I could be expected to have to folk out on. House on side of a field gets very wet in winter, current cellar about 7 foot beneath ground level. I presume that if I did get go a head and Building Controls gave me the nod that i'd be tanking up the walls during the build.
Regardless of that not a clue!
Thanks for any input.
KB
PS LCL What's -KSI?

[andysarah]

Hi,
Basement construction is very dependents on whether you can dig a big hole or not; if you can then you can put in the base, build the walls and then back fill, where as if you cant, due to say adjacent buildings, then you have to hold back the ground around the basement and build something within. I have done both types of structures. waterproofing is all important, if it is not considered and detailed correctly at design stage then the whole exercise could be difficult in the final situation with damp/water running in etc. I would recommend getting a suitable experience engineer to advise once planning is granted.

KSI Kent site investigation run by a guy called Andy? I have met the guy but I work for a Kent based consulting engineers called Crofton Design based in Hadlow, we have a website if you are interested.

Kind regards Andy Locke MIStructE

[Achab]

[quote="andysarah"]Hi,
Basement construction is very dependents on whether you can dig a big hole or not; if you can then you can put in the base, build the walls and then back fill, where as if you cant, due to say adjacent buildings, then you have to hold back the ground around the basement and build something within. I have done both types of structures. waterproofing is all important, if it is not considered and detailed correctly at design stage then the whole exercise could be difficult in the final situation with damp/water running in etc. I would recommend getting a suitable experience engineer to advise once planning is granted.

KSI Kent site investigation run by a guy called Andy? I have met the guy but I work for a Kent based consulting engineers called Crofton Design based in Hadlow, we have a website if you are interested.

Kind regards Andy Locke MIStructE[/quote]

Agree with you andysarah, thanks for the great post


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[grant01]

Hi 'andysarah',

I am lucky enough to be able to dig the big hole and put in the base then the wall and back fill, my area is west yorkshire, well above the water table the soil type is sand stone layers and clay.

I am currently looking into the sealing systems for the cellar, Vandex or Olroyd system, both arnt cheap. Do you have any preferances/ recomendations? or a cheaper way??

Regards

Grant

[andysarah]

hi,
i only recommend caltite concrete additive, it doubles the concrete price but once the walls and slab are poured the job is finished. no trying to stick sheets on or rendering after the walls have got wet and muddy from general site work etc. they also give a gaentee to the baseemnt, which is unusal. if it leaks they repair it with out extra costs. if a sheet system leaks its your problem and the system is on the out side of the basement so the leak could be any where!!!! i have specified various sysytems over the years but now i only spec caltite!

[grant01]

Thanks, andysarah.

That’s great, I will look into it.

It certainly seems a simpler way than the ones I have been looking at, especially if it guaranteed also.

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[kanneii]

building rooms below ground will create loads of problems and some of them might be like ground water, high water tables, etc.

I would rather say go for a professional consultant/engineer.