Sjk

(Update) Foundations on a site of archaeological interest

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I need to come back with some proposals for our foundations, short story is there are archaeological findings under where the house was planned to be (can't move it), so the preferred solution is to come up with some foundations which will not disturb them.

 

I have been doing some research and wondered if a raft or piling foundations could be the answer? Raft should be shallow(?) and piling could be guided to safe areas.

 

Bit concerned with a concrete slab as if there is an issue with say utilities under the slab it would be a nightmare to repair, that said piling concerns me too! I would need to find out where we can go, the archaeological fees have already been expensive, so want to try and keep it to a minimum. 

 

The house is brick and block, the footprint is only around 40-45m2.

 

Any ideas?

Edited by Sjk

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Why be concerned about services, any build method will have services under the floor in one way or another

put ducts in so you can pull pipes or cables in. 

If you have underfloor heating you will bury it all in the floor

its something that happens when you build a house, the only way to avoid it is to build a house on stilts and crawl under to get to services. 

With your small footprint you can build a very nice insulated slab for not a lot of money, minimal ground disturbance, you could lay temporary road mats over the rest of the site to save disturbing it. 

Do you have to provide a method statement to satisfy anybody. 

 

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Thanks.

 

Yes, as far as I'm aware we do have to, to satisfy the archaeologist. 

 

Fair point regarding the construction, I was thinking about if there was a water leak they may have to cut/smash the floor to repair it.

Edited by Sjk

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9 hours ago, Sjk said:

Bit concerned with a concrete slab as if there is an issue with say utilities under the slab it would be a nightmare to repair,

An insulated raft is the way to go. The services don’t have to go under the slab, they could be kept to the edges with th3 right house layout.

 

This learned report from the Museum of London might help

 

https://www.mola.org.uk/sites/default/files/downloads/Mitigation of construction impact A4.pdf

Edited by Triassic
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Have you got an archaeologist on board? Do they need to do any surveys or have a watching brief requirement?

I've done a few projects with archaeology around and we've never really had to change any foundation design, just had to either report and protect what's there or had the Archaeologist agree that there was nothing significant there...

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Did you watch the first episode of grand designs  new series a few weeks back.  It showed how much of an issue this can be. Not sure if it's still on 4od if you missed it. 

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Thanks for the link, I'll give it a read.

 

We have an archaeologist, they have just finished trenching and before that they did a DBA. The archaeologist is getting the final report ready, but they have said we should suggest the least invasive foundations to not disturb the site and try to settle for a watching brief.

 

I must have missed GD, I'll watch that thanks!

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Pity you couldn’t have the sever pipe route preplanned, their archilogival trench could have followed the same route, save you digging later!

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Forgive me for digressing but if anyone is going to build over “old” stuff why not dig it up and preserve it elsewhere or document it? I think there are too many listed buildings, yes keep a few for historic reference but !!!!

 

(hard hat at the ready).😳

Edited by joe90
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It will be fully documented, there is a structure underneath so not sure digging it up would be an option.

 

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3 minutes ago, Sjk said:

It will be fully documented, there is a structure underneath so not sure digging it up would be an option.

 

Do you know what it is/was?

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4 hours ago, joe90 said:

Do you know what it is/was?

 

Unfortunately not at the moment, I will get the full report next week. 

 

 

 

 

It looks like they have puled that episode of grand designs.

Edited by Sjk

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If is not economical / practical to avoid the stuff underneath, argue this with the archaeologist as unless the finding is of significant importance it should not be an obstacle preventing development.

 

I have had similar with trees in conservation area and they conceded that keeping them was not practical.

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18 hours ago, Mr Punter said:

If is not economical / practical to avoid the stuff underneath, argue this with the archaeologist as unless the finding is of significant importance it should not be an obstacle preventing development.

 

I have had similar with trees in conservation area and they conceded that keeping them was not practical.

 

Is that really the case? The council seem to want me to spend as much as possible and don't seem to want to enter into any negotiation.

 

Perhaps we need to go harder. 

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Where we are it used to be the case that archaeology was funded by the County Council and we used to just have to ask the local voluntary archaeology group to visit any sites which were considered of interest.  I think we donated about £100 per house.  Now it is "developer funded" and it has spawned a whole business and the fees are now about £1000 per house.

 

If the planning condition means that you are not able to reasonably construct foundations and the actual worth of the archaeology is low you can appeal the condition.  On the other hand if your site overlies a Roman villa with intact mosaics you may need to think again!

 

Explain to the archaeologist what foundation system you are proposing and why and see what he suggests, as it is you that pays his fees (through gritted teeth no doubt).

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The first site we were going to buy had a lot of buried archaeology; it was the site of an old water mill dating back to Anglo Saxon times.  Two big exploratory trenches had been dug at the expense of the vendor, when they got outline PP, and these found lots of evidence for there being a mill on the site going back well over 1000 years. 

 

I proposed using screw piles as a foundation solution, to minimise disturbance to the buried archaeology, but this was rejected.  A raft was acceptable, but there was an insistence on an archaeologist being present for all excavations, who would have the authority to call a halt to work and order a full excavation of anything they found, at our expense.  I had estimates for this and they were very open-ended.  The archaeologist said that they were near-certain that there would be significant finds during any excavation work on site, and that the costs were likely to be at least £20k and could be well over £100k, depending on how long they took to excavate and record everything they found.

 

For other reasons we walked away from the purchase, but I had the strong feeling that we'd have had to pull out over the unknown cost of the archaeological work, anyway.

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I’ve had some preliminary feedback from my archaeologist today. 

 

They were suggesting raft, but my architect was against this solution for some reason. 

 

They are saying at the moment they are saying there is 200mum to play with, although I am waiting for them to clarify if that is on top of the hard standing which must be at least 200mm itself. 

 

Im feeling screwed!!

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'Preservation in-situ' is an established archaeological principle.  In the bad old days a lot of sites were excavated for the fun of it and the resource destroyed as a result.  With the technological advances that have happened since, we could learn so much more from those old sites if they hadn't been destroyed (excavation being nothing more than controlled destruction after all).  So now the first rule of archaeology is always to preserve in-situ and only excavate if absolutely necessary or unavoidable.

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On 06/11/2018 at 11:02, JSHarris said:

The first site we were going to buy had a lot of buried archaeology; it was the site of an old water mill dating back to Anglo Saxon times.  Two big exploratory trenches had been dug at the expense of the vendor, when they got outline PP, and these found lots of evidence for there being a mill on the site going back well over 1000 years. 

 

I proposed using screw piles as a foundation solution, to minimise disturbance to the buried archaeology, but this was rejected.  A raft was acceptable, but there was an insistence on an archaeologist being present for all excavations, who would have the authority to call a halt to work and order a full excavation of anything they found, at our expense.  I had estimates for this and they were very open-ended.  The archaeologist said that they were near-certain that there would be significant finds during any excavation work on site, and that the costs were likely to be at least £20k and could be well over £100k, depending on how long they took to excavate and record everything they found.

 

For other reasons we walked away from the purchase, but I had the strong feeling that we'd have had to pull out over the unknown cost of the archaeological work, anyway.

 

Just read your post again, 20k-100k is eye watering! I suppose they got very excited about the old water mill :(. Wonder if the site was ever developed?

 

I have been looking at screw foundations, the damage should be minimal as they are tiny compared to other piled solutions. Very disappointing to hear that

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9 hours ago, Sjk said:

 

Just read your post again, 20k-100k is eye watering! I suppose they got very excited about the old water mill :(. Wonder if the site was ever developed?

 

I have been looking at screw foundations, the damage should be minimal as they are tiny compared to other piled solutions. Very disappointing to hear that

 

The vendors had a team in from Bristol University who had dug two big trenches across the plot already, and found loads or stuff, including millstones, a cobbled floor, the remains of walls, etc, and the old mill leat was still visible running through the woods that formed the rear of the plot, as was the wheel pit at the back of the plot.

 

I took a detour back past the plot around 3 years after we walked away from it and it was still empty, so my guess is that others walked away much as we did.

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