Basement Digging

[BruceyP]

Hi Guys

Im looking to dig out my basement for conversion into habitable rooms. I will be doing this myself as a competant DIYer.

I've been in contact with a structural surveyor who has advised me on digging 4 trial pits to inspect the current foundations which I have completed. Current head room is 2100mm and im looking for around 2600mm of headspace. The base of the footings extend 800mm down.

I plan to dig out the entire basement to level with the base of the footings. Then backfill with 100mm of compacted stone and then with 125mm of concrete slab based on his calculations. Then insulate, board and floor above the waterproof membrane depending on what building regs require.
Ill tank the basement with membrane and use a sump & pump system for any groundwater issues (everything dry so far bar damp walls)

I have two questions: Firstly does this sound OK to you? I was a little concerned about my neighbours basement level being higher than mine and if this would put a strain on the wall but the surveyor has assured me that 2 foot difference would be ok.

Secondly, is there any sort of DIY public liability insurance that I can get that will cover me for this sort of work without registering myself as a company? I dont think this will be covered under my standard DIY cover under the house insurance policy.

Any info would be most appreciated.

Cheers

Bruce

 

[simonjay]

Hi Guys

Im looking to dig out my basement for conversion into habitable rooms. I will be doing this myself as a competant DIYer.

I've been in contact with a structural surveyor who has advised me on digging 4 trial pits to inspect the current foundations which I have completed. Current head room is 2100mm and im looking for around 2600mm of headspace. The base of the footings extend 800mm down.

I plan to dig out the entire basement to level with the base of the footings. Then backfill with 100mm of compacted stone and then with 125mm of concrete slab based on his calculations. Then insulate, board and floor above the waterproof membrane depending on what building regs require.
Ill tank the basement with membrane and use a sump & pump system for any groundwater issues (everything dry so far bar damp walls)

I have two questions: Firstly does this sound OK to you? I was a little concerned about my neighbours basement level being higher than mine and if this would put a strain on the wall but the surveyor has assured me that 2 foot difference would be ok.

Secondly, is there any sort of DIY public liability insurance that I can get that will cover me for this sort of work without registering myself as a company? I dont think this will be covered under my standard DIY cover under the house insurance policy.

Any info would be most appreciated.

Cheers

Bruce

You can get self build insurance (google it). About 5 years ago it was fairly cheap. Usually "self builders" are project managing other contractors, so make sure you tell them it is DIY.

I needed it to protect neighbours when digging next to their wall and removing my half of a concrete slab roof on an outhouse etc.

Since I was DIY, they wanted plans / photos of how I was doing any of the "risky" things.

It protected against site loss, public liability, etc.

Simon.

 

[BruceyP]

Thanks Simon, thats really usefull. My only question about this would be how much protection does a policy like this offer.

For instance the work could run smoothly and and accident free until completion but then perhaps 5 years later cracks could appear due to an issue with the foundations etc.

Would the work still be protectd then? Would I even be liable?

Cheers

Bruce

 

[jeds]

Have you applied for planning permission and building regulations? And have you served notice under the party wall act. If you do neither of these insurance won't help you if things go wrong.

 

[BruceyP]

You don't actually require planning for this work in my area but building regs will obviously apply. However I will be submitting a full plans approval so that any issues in design can be resolved early on. I haven't submitted anything yet as surveyor hasn't given me any paperwork from his inspection yet.

I also don't require party wall agreement as I wont be undermining the neighboring walls. Under section 6 of the act it states you only require it if you dig lower than the neighboring foundations.

 

[jeds]

I was a little concerned about my neighbours basement level being higher than mine...

??

 

[BruceyP]

Ahh yes, by this I mean finished floor level. So at the moment the party walls extend 2 and a half foot down below my current and floor level (which will also be my neighbours floor level) to the underside of the footings. As I will be digging down level with the footings this floor level will be below their floor level but not below the footings of the party walls.

Hope that makes sense.

 

[handyman77]

Did your engineer so it was ok to dig out the basement in one go? We had to stagger and dig 1 Sqm at a time, this could avel been due to ground conditions in my case. I would check if I was you!

 

[BruceyP]

thanks handyman, thats interesting.

Are you sure you werent underpinning? Or where you just digging out the basement. I know digging 1m sections is common when underpinning but I will only be digging level with the foundations rather than undermining them.

 

[handyman77]

when digging out the soil/clay you are exposing it to the air which can dry it out and create shrinkage of the ground (This is what i was told by an engineer) although your not undermining it, it can still dry out if left for a length of time. This was based on a victorian propertie with shallow foundations, it might not apply to you! just thought i would raise the question.

 

[BruceyP]

Thats great handyman! Certainly worth mentioning and thinking about. The soil covering my footings is clay and very wet and sticky. I actually posed a similar question about the drying out of the soil underneath the footings to my surveyor in relation to the sump and pump. He didnt think it would be a problem but im all to aware of so called expert advise having to be taken with a pinch of salt.

The clay will be covered with crushed stone and concrete slab so it will hopefully be kept moist. I also plan and making the sump as shallow as possible (and setting the pump float switch at the highest available setting)so as not to dry out too much of the clay.

 

[handyman77]

Just thought id mention it! Is your surveyor an experienced (old!) guy?
I would like to think so, as Ive seen many a university graduate that aint got a clue! Also sometime a structural engineer is better to advise I know its not underpinning but.....
if hes old school I would presume he knows what hes talking about as opposed to have read it out of a book in the classroom.
Theres no experience like experience...
good luck!!

 

[catlad]

Why do you want to go to all that effort when you already have 2.1m head height.

 

[handyman77]

He's 6 ft 6 and when he's wearing his stillettos his head hits the ceiling!

 

[BruceyP]

Hahahah what a man does in the privacy of his own home is his business!!!

Although 2.1m seems like enough when you consider adding 4 inches of insulation to the floor, half an inch of screed or boarding and then your flooring not to mention the plaster board and light fittings; at 6ft my head is going to be grazing the ceiling and it wont be pleasant.