SamUK

iTrader: (1)

Hi,

Just finalising the last few bits before i give the builder the go-ahead to start the building work on the house.

I am having a single story rear extension made.

The builder has agreed a price, however said they will only dig the foundation 1.2m - this is the typical size! He initially said this depends on the type of soil etc and he will know if it needs to go more after he has dug it out. Additional cost will apply for materials if this is the case..

So i questioned him, and said come down dig a trench and tell me for definite how deep the foundation needs to be.

His response was can not do that as it is the council who do a site visit to approve the depth before they fill the hole with concrete..

Is this the case?

and is 1.2M usually the depth the foundation is dug?

mamoon2

Yes.

Surely you have agreed a fixed price for the build?

People replied to you last post but you never bothered to come back and reply

500

As above, the builder is right, 1.2 is around the usual depth but the building inspector will have final say, you need to dig down and hit solid ground, i.e clay.

I would agree on a fixed price subject to the depth of foundations needed

ChefDude

yup, happened to us. in fact, with the 'close' proximity of a tree, the official made my builder dig to 2m.

SamUK

iTrader: (1)

Odd...i never got emails from Scoobynet for replies..

A fixed price has been agreed but the builder said max 1.2m, anything more required will cost extra.

I think it is clay soil - there is a tree near 8M high but this is being cut down

SamUK

iTrader: (1)

Also what is a Party Wall Agreement? do i need one?

The neighbours have verbly said they do not have issues, aslong as the wall does not fall on the neighbours side of the house.

Hysteria1983

I would imagine your builder has a rough idea of a max depth he would need to dig. He can't dig forever. Get a price for the 1.2, and get another max price if he needs to dig further.

Being honest if the builder is expecting you to agree to work without a price this early then I would be very wary.

My builder agreed a price with us from start to finish. We agreed to pay him in installments at set points throughout the build and that was that.
Not a penny more.

Dingdongler

Sam, there were lots of replies on your last thread including from professionals like Pacenote and Alan Bell.

Hysteria1983

Did you subscribe to the thread?

Tidgy

builde ris just covering his **** in case theres issues, can;t blame him realy. on big projects full ground investigations are done to make sure all is ok, for a private dwelling they would be way to expensive to need it

Coffin Dodger

Sounds dodgy, are you working to a written quote (legally binding) or estimate from your builder. If he is already trying to find excuses to bump the costs at the groundwork stages imagine what other stuff he might come up with throughout the build.

Ours was to a fixed cost with instalments at four pre-agreed stages. We did agree to not include things like electrical work (except what was required by the regs. i.e. smoke detectors, extractors, etc.), kitchen supply and fit, and finishing in the initial quote so they they could be thrashed out as the build progressed. Everything else was included.

As mentioned the building inspector will need to visit to sign off the foundations before concrete is poured into them. They need to be deep enough to hit the sub soil layer.

SamUK

iTrader: (1)

Found it...

I will read this and use this

https://www.scoobynet.com/non-scooby...ion-costs.html

Tidgy

depends on situation, if other properties are close and when they dig they find bad conditions they may have to add underpinning etc, to me a fixed price would push the builder to take shortcuts and you'd eny up with major issues down the line

Dingdongler

I think it's quite standard practice. My builder was upfront about this when I had my extension done. He quoted for a standard depth of foundation and said how much extra it would be for each extra meter he was made to dig.

The builder can't predict what is under there and how much further the building regs inspector might demand you dig.

Iirc Sam you live in Loughton which means Epping council and they are VERY strict.

legb4rsk

Also the builder may find sewer/water/gas/electricity under where the foundations are going.The sewers ran down the back of our property & where expensive to move.

mattstant

Any builder worth his reputation would do exactly the same.
Ground conditions cannot be safely predicted and will only be passed by a building isnpector in situ.
foundations have to be reach a firm bearing strata and that could be 150 mm below the surface or beyond 2m (although probably not).
Costs to dig below 1.2 m can be come exponential so the caution by your builder in my opnion (backed might i humbly add with 30 odd years in house building and an hnc in construction) shows he knows his onions and is being cautious on costs.
If your are particularly worried you could fix a cost of so much per say 600mm beyond the 1.2 as we would do with any external contractor.

Aaron1978

iTrader: (12)

The tree part is quite important, as although you're cutting it down that tree removes a certain amount of moisture from the ground. This could cause the clay/soil to swell and then heave and the end result could be broken foundations and even the floor pushing upwards. What kind of tree is it? as some tree absorb up to 50,000 litres of water a year to give you an idea of how wet your soil could become. What sort of floor are you having? suspended?

Aaron

Oh and your builder is right to be cautious. I've just done a footing where the ground report said we would hit clay at around 1.5m from existing level when in fact we hit it at 2.7m. Which resulted in the the amount of concrete increasing from 12 m3 to 50 m3.

Jonnys3

Party Wall explained

Dingdongler

azz, what do you do mate?

Aaron1978

iTrader: (12)

Construction/Civil Engineering/Ground works.

We build roads & sewers and then houses up to DPC for Barratts, Persimmon, Bellway homes and Harron homes as well as projects such as Schools, depots, industrial units.

Aaron

kj200sx

iTrader: (7)

my old house sufferd from heave just 1 year after it was built after a further 3 years of battling builder nhbc etc they finally had to buy it back as repair bill was upto £86000 which at the time was 60 % of the value so builder had to by law but agree tree can cause major problems

john_s

iTrader: (1)

We've had a couple of (industrial) jobs where the foundations ended up deeper than expected. On one, most of the foundations were about 1.5m deep, but the clay took a dive towards the end of the building and the last pad foundation had a JCB digging right at full stretch, something like 6m deep, and it needed about 30m3 additional concrete to bring the level back up.

Another job saw a similar situation on several pad foundations, except this time the problem was compounded by contaminated sand. It smelt like diesel, looked the colour of used engine oil, had the consistency of porridge, and just ran into the excavation. As well as the holes going deeper, they were growing outwards too as the sides fell in. In addition to the extra concrete (approx 150m3 on the job IIRC), the client had a huge bill for the disposal of the contaminated ground. It was amazing to see a 6m3 wagon load of concrete just dropped straight into the hole and make little apparent difference to the level.

Fortunately in both cases, the Building Inspector was happy with just seeing the clay and didn't want to go down and test it, or the client would have had further expense for propping to make it safe for someone to go down the hole.