Might need piles and planning question
Discussion
I'm considering building an extension on the back of my house, the original house is about 15 years old and is built on a concrete raft with a pot and beam floor, so obviously the ground is pretty bad for conventional footings.
I have dug an inspection hole down to around 1 metre, its just general soil with stones mixed in etc, no sand or clay etc. Whats the best way to proceed, if I continue to dig a trench down will it cock it up for the piling which will have to be done or can the trench just be back filled and then piled? Its only a small extension, 5Mx3M double story.
Second question is on planning, the PD rights have been relaxed recently and I can now build a 2 story extension 3M out without any planning permission. Except I fall foul of the rear boundary distance, apparently the fence has to be 7M away from the extension, mine is only 6M, however behind the fence is a couple of metres of scrub land, then a lane and then across from that some farm outbuildings/containers etc, its not overlooked at all.
I would rather not go down the planning route if I can help it, I was thinking of moving the fence back into the scrub land or taking it down altogether so there is no boundary. The fence is a bit of an odd shape at the back anyway and I was thinking of straightening it up at some time, would pulling a fast one like this open up a world of hurt with the council? you know how they get if they cant dictate this and that to you whilst wearing a high viz and carrying a clipboard. Or is the 1M discrepancy so minor it makes no difference.
Just to be clear its not the planning fees that I'm trying to avoid, just the weeks of nazi officialdom.
I have dug an inspection hole down to around 1 metre, its just general soil with stones mixed in etc, no sand or clay etc. Whats the best way to proceed, if I continue to dig a trench down will it cock it up for the piling which will have to be done or can the trench just be back filled and then piled? Its only a small extension, 5Mx3M double story.
Second question is on planning, the PD rights have been relaxed recently and I can now build a 2 story extension 3M out without any planning permission. Except I fall foul of the rear boundary distance, apparently the fence has to be 7M away from the extension, mine is only 6M, however behind the fence is a couple of metres of scrub land, then a lane and then across from that some farm outbuildings/containers etc, its not overlooked at all.
I would rather not go down the planning route if I can help it, I was thinking of moving the fence back into the scrub land or taking it down altogether so there is no boundary. The fence is a bit of an odd shape at the back anyway and I was thinking of straightening it up at some time, would pulling a fast one like this open up a world of hurt with the council? you know how they get if they cant dictate this and that to you whilst wearing a high viz and carrying a clipboard. Or is the 1M discrepancy so minor it makes no difference.
Just to be clear its not the planning fees that I'm trying to avoid, just the weeks of nazi officialdom.
I would want to know what the ground conditions are. Why a raft and not piles in the first place? (probably cost but not always) I would have though that if the house is on a raft and the extension on piles the risk of differential movement would be quite high.
If you pile it, what design and structural info do you have to tell you how deep the piles should be, what type of pile, what size ground beam etc?
If you pile it, what design and structural info do you have to tell you how deep the piles should be, what type of pile, what size ground beam etc?
blueg33 said:
I would have though that if the house is on a raft and the extension on piles the risk of differential movement would be quite high.
Be very aware of this.Seen countless properties with either an extension or a conservatory with this problem.
"Oh but they dug down very deep!"
Yes but your house is built on a raft bla bla bla.
We're in a similar boat with an extension and have had design/drawings done so, size wise, it should fall under Permitted Development.
We only had the drawings done this week but our Architech has advised he still sends them off to planning Dept to get a "Lawful Development Certificate". (Costs £86.00). From what I understand it's not actually applying for planning but just gives 100% proof that the extension has been permitted and there will never be any comeback, especially when coming to sell house in future etc..
I kind of feel it's tempting fate (especially as it also mentions on the drawings we will be changing the windows from stained wood to anthracite UPVC throughout) but I'm being guided by what the Architech reckons.
https://www.gov.uk/guidance/lawful-development-cer...
We only had the drawings done this week but our Architech has advised he still sends them off to planning Dept to get a "Lawful Development Certificate". (Costs £86.00). From what I understand it's not actually applying for planning but just gives 100% proof that the extension has been permitted and there will never be any comeback, especially when coming to sell house in future etc..
I kind of feel it's tempting fate (especially as it also mentions on the drawings we will be changing the windows from stained wood to anthracite UPVC throughout) but I'm being guided by what the Architech reckons.
https://www.gov.uk/guidance/lawful-development-cer...
I'd always advise getting a certificate of lawful development to be on the safe side.
I have in the past had some very odd reasons for deciding the an application was not permitted development.
I had one recently where we did a single story rear extension to an old property, submitted it and it was rejected as they considered the rear of the building to have originally been the side elevation, as the original road 100 years ago ran at 90 degrees to the current road layout.
For the sake of £80-90 I'd want the piece of mind.
I have in the past had some very odd reasons for deciding the an application was not permitted development.
I had one recently where we did a single story rear extension to an old property, submitted it and it was rejected as they considered the rear of the building to have originally been the side elevation, as the original road 100 years ago ran at 90 degrees to the current road layout.
For the sake of £80-90 I'd want the piece of mind.
I'd also recommend building as big as you can while you're messing about. We did our part 2 storey rear and part 1 storey side extension under PD 5 years ago and went back 3m. For the sake of a planning application (which you can do yourself) I should have gone back the full 4m.
We are about to extend ours again to go into the drive. Again, I wish I'd just done this all at the same time but we didn't know we'd really need another bedroom back then. Oh and our existing extension is piled - 9 of the buggers going down 14m each. The piling and ground beam cost over 5k and it seemed excessively over engineered to me. The side extension is going on a strip footing. It'll be interesting to see if it all goes to s
t then!
We are about to extend ours again to go into the drive. Again, I wish I'd just done this all at the same time but we didn't know we'd really need another bedroom back then. Oh and our existing extension is piled - 9 of the buggers going down 14m each. The piling and ground beam cost over 5k and it seemed excessively over engineered to me. The side extension is going on a strip footing. It'll be interesting to see if it all goes to s
t then!blueg33 said:
I would want to know what the ground conditions are. Why a raft and not piles in the first place? (probably cost but not always) I would have though that if the house is on a raft and the extension on piles the risk of differential movement would be quite high.
If you pile it, what design and structural info do you have to tell you how deep the piles should be, what type of pile, what size ground beam etc?
These are the things I need advice on, I have no idea why the house was built on a raft, I am almost certain it is a raft from what the neighbours tell me, when we dug the inspection hole against the side of the house the bricks were sat on a concrete foundation a bit wider than the house but with a very rough side to the concrete, not at all like the side of a concrete footing I have seen before. Also its definitely a pot and beam floor as inside its a screed finish that you can tell is hollow underneath, also there are air vents round the outside.If you pile it, what design and structural info do you have to tell you how deep the piles should be, what type of pile, what size ground beam etc?
What would be the best way to add an extension to a house that is built on a raft, maybe if I did a bit deeper then conventional footings would be ok, who knows. Its only a small cul-de-sac I'm on and the house at the other end had an extension and their conventional foundations only went down the minimum, the ground was perfect for building on.
mickmcpaddy said:
What would be the best way to add an extension to a house that is built on a raft, maybe if I did a bit deeper then conventional footings would be ok, who knows.
Didn't read my post then?As the post above suggests, you may want to keep the same with a movement joint.
On the face of it I wouldn't recommend tieing into the existing structure.
Is it on a raft or is it trench fill? You cant know without the original design info. How old is the house? I would ask building control if they have info on the foundations.
Developers wont use a raft or piles if they don't have to. In most cases there are cheaper alternatives. Eg sandy or gravelly soils can take vibro, mini piles are cheaper than rafts generally, deep trench fill is cheaper than all the above.
If the house is recent, try asking the nhbc.
Developers wont use a raft or piles if they don't have to. In most cases there are cheaper alternatives. Eg sandy or gravelly soils can take vibro, mini piles are cheaper than rafts generally, deep trench fill is cheaper than all the above.
If the house is recent, try asking the nhbc.
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