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Well that's a poke in the eye with a pointed stick


LSB

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I haven't posted to my blog for a couple of months, mainly because we haven't been able to progress until we got the Structural Engineers report.

This was promised in 2 weeks and ended up taking 10.

 

I now suspect that this was because they didn't want to tell us the news.

 

Our build is a barn conversion so we've had to jump through lots of hoops. ,making lots of money for other people.

 

But, particularly for the SE, first it was the report where they said to planning that the barn was convertible.

 

Then the 1st phase ground contamination report, no issues there.

 

Planning approved with condition of phase 2 contamination report.

 

So, back to the SE to do this, no problems with that.

 

Then we started preparing the site, documented in previous blogs, we did this thinking that it would benefit us with the SE report to get the building regulations drawn.

 

How wrong we were.

 

One of the limitations of the barn conversion was that one side of the building can only be 2.2m high.  We worked around this by designing rooms so it wasn't needed for walking.

 

Yesterday, I received the report, only to be horrified to see that this low side of the building, 2.2m remember, needs underpinning foundations of 'at least' 2.4m.  How can a single storey build possibly need foundations deeper that the height of the building.

The opposite side is 3.15m high to the roof, here the SE say we only need 1m deep foundations, figure that out.

 

The soil is not clay, not sand, there are a few 3" elm trees that are being knocked down so no large roots.

 

But, it gets worse,  they say that this must be done 1m at a time, doing 1st meter, then 3rd meter, then 5th meter, then 2nd meter etc.etc.

This particular wall is 25m long.

 

They have no issues with the existing internal walls.

 

 

I've never been so glad to be stupidly busy at work to take my mind of this fiasco.

 

So, what do we do.

 

The thoughts I have are:

 

1. Can we knock down the back wall leaving the rest and build only 1m deep like the wall on the opposite side,  but I would still need to get planning.
 

2. Do we write off all the work we've done and all the money we've spent (lots) and try and get planning to start from scratch with a kit house.  It would have to be self build though due to the extremely limited funds available.

 

3.  The long wall splits into utility, 2 x bathrooms, 3 x bedrooms and a pantry.  Do we knock down the wall for each room and then rebuild it bit by bit and with what foundations.

 

4.  Do we start on the high side of the conversion and work backwards ignoring the problem for now.

 

The sides vary from 1m front to 2m foundations at the back.

 

The most disappointment I feel is that the SE passed the building as fit to convert, including digging holes to look at the existing foundations with no mention of anything like this.

I don't know if it makes any difference, but the original SE was probably about my age, in his 50's, whereas the recent one (same firm) was barely out of nappies and didn't want to talk to us when he was here to discuss anything.

 

What I have done is:

 

a. Requested a meeting with the SE and his manager to ask why so deep and about a new wall.

If we can knock down the wall and put in 1m foundations then that is manageable as with the digger we can knock the existing one down and dig the trenches before getting a groundworks crew to do the rest.

 

b. Started compiling an email to send to the planners, but with the current situation I don't think I will hear anything.  Also, I'm a bit wary, if we say what is required can they pull our planning and still not allow us a new build.

 

c. Started looking at some kit companies who provide self build kits to get some ideas of costs.

 

The one thing that we cannot do is dig down 600mm x 2.4m a meter at a time.  Maybe a groundworks company could, but at what cost for what, in reality, is a tatty barn which, if we could have got planning we would gladly have knocked down and crushed.

 

I spoke to the planners after we got planning to ask about this route and we told that we had no chance.

 

Here's a little reminder of the layout.

 

layout.thumb.png.91dd28a357789666ffbac19709c2d1e5.png

 

The wall is the bottom one up to where the ensuite wall is and the top of the WC on the left.

 

I now feel so demoralised, building is stressful for many reasons, but I didn't expect it to be quite so impossible.

 

Time for whine I think ?

 

Enjoy the heading picture of the kittens, to cheer me up.

 

 

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I'm doing a stable conversion too and it's been very slow and painful, with so many constraints, as you are finding, it seems much more difficult than designing and building something new. I got another structural engineer's opinion and it was different. The first said underpin all round, the second said it was ok not to if we didn't dig the ground bearing slab out. 

Edited by Jilly
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1 minute ago, Jilly said:

 

I'm doing a stable conversion too and it's been very slow and painful, with so many constraints, as you are finding, much more difficult that building and designing something new. I got another structural engineer's opinion and it was different. The first said underpin all round, the second said it was ok not to if we didn't dig the ground bearing slab out. 

thanks,  that's encouraging.

I've got a meeting with the SE & his boss tomorrow over the phone so I'm going to ask some more questions.

 

But, going to a different SE might work.

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Hopefully Gus will be along soon. Maybe post for advice on the main forum?

 

 

Edited by Jilly
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@LSB. What a pain. I feel for you. Self  building is tough on a greenfield site never mind having to deal with the issues of kicking an agricultural building, dragging and screaming, into a modern house. 

 

To me it seems absolutely ludicrous one cannot simple demolish and replace the exist structure with something externally identical. I suppose that's beside the point. Perhaps, given the reality of the works to be undertaken, the planners would now have some sympathy to this position?

 

Secondly about the SE. If they are quite new to the role they are naturally very cautious, infact the exact right personality to be an engineer, however they may not have the experience to know exactly where the line is. Hopefully a senior colleague will have better news. 

 

As an alternative solution, maybe contact a local underpinning firm for a consultation. They may well have a cheaper solution that your SE will be happy with given their more in-depth knowledge of the situation. 

 

Good luck. 

 

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Well @LSB, stepping back from the situation, the depth to me seems odd. 

 

As I understand it, foundations are used to ensure the weight of the building is dispersed over a ground surface area capable of supporting the structure plus a factor of safety.

 

So larger surfaced than usual foundations usually indicate either a heavier building or dodgy ground or a point load - say a pad foundation for a steel.

 

Deeper foundations point to poor ground or tree roots.

 

The only time I've known  2.4m deep underpinning was because the roots from a mature oak tree 10 meters away were undermining the foundations of a house.

 

If there isn't anything indicating tree root potential then it has to be poor ground and the only way to tell how far to go down is to dig a trial hole or bore down to see where the good ground starts.

 

Other things of note are sites with steep sloping ground or near other properties or your going for a basement.

 

This is the limit of my knowledge so I leave it to others to point out my failings. 

 

You need to get to the bottom of this. (Sorry I couldn't resist)

 

All is not lost! Hang in there. 

 

Best of luck

 

Marvin. 

 

 

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9 hours ago, Iceverge said:

@LSB. What a pain. I feel for you. Self  building is tough on a greenfield site never mind having to deal with the issues of kicking an agricultural building, dragging and screaming, into a modern house. 

 

To me it seems absolutely ludicrous one cannot simple demolish and replace the exist structure with something externally identical. I suppose that's beside the point. Perhaps, given the reality of the works to be undertaken, the planners would now have some sympathy to this position?

 

Secondly about the SE. If they are quite new to the role they are naturally very cautious, infact the exact right personality to be an engineer, however they may not have the experience to know exactly where the line is. Hopefully a senior colleague will have better news. 

 

As an alternative solution, maybe contact a local underpinning firm for a consultation. They may well have a cheaper solution that your SE will be happy with given their more in-depth knowledge of the situation. 

 

Good luck. 

 

 

They are a well established and locally well respected SE company.  My only thought is that most of the work they do is commercial rather than residential so maybe they are used to deeper pockets.  They did the original ground survey and raised no issues with the ground, I'll dig out the report and see what the exact terminology was.  The site is as good as flat, maybe 10 degrees.  The building is at the edge of the site, but I can't imagine that the ground changes much in 9m, the distance between the back (2.4m) and the front (1m)

 

Anyway, talking to them today so I'll have more details then.

 

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46 minutes ago, Marvin said:

Well @LSB, stepping back from the situation, the depth to me seems odd. 

 

As I understand it, foundations are used to ensure the weight of the building is dispersed over a ground surface area capable of supporting the structure plus a factor of safety.

 

So larger surfaced than usual foundations usually indicate either a heavier building or dodgy ground or a point load - say a pad foundation for a steel.

 

Deeper foundations point to poor ground or tree roots.

 

The only time I've known  2.4m deep underpinning was because the roots from a mature oak tree 10 meters away were undermining the foundations of a house.

 

If there isn't anything indicating tree root potential then it has to be poor ground and the only way to tell how far to go down is to dig a trial hole or bore down to see where the good ground starts.

 

Other things of note are sites with steep sloping ground or near other properties or your going for a basement.

 

This is the limit of my knowledge so I leave it to others to point out my failings. 

 

You need to get to the bottom of this. (Sorry I couldn't resist)

 

All is not lost! Hang in there. 

 

Best of luck

 

Marvin. 

 

 

 

As my hubby said this is the low end of the building with a flat roof so it will be taking the majority of the weight.  I'm also going to talk to the SE about steels to support the roof, which don't seem to have been specified.

 

No basement, just a single storey build with a flat (12 degrees) metal roof.

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9 hours ago, Iceverge said:

@LSB. What a pain. I feel for you. Self  building is tough on a greenfield site never mind having to deal with the issues of kicking an agricultural building, dragging and screaming, into a modern house. 

 

To me it seems absolutely ludicrous one cannot simple demolish and replace the exist structure with something externally identical. I suppose that's beside the point. Perhaps, given the reality of the works to be undertaken, the planners would now have some sympathy to this position?

 

Secondly about the SE. If they are quite new to the role they are naturally very cautious, infact the exact right personality to be an engineer, however they may not have the experience to know exactly where the line is. Hopefully a senior colleague will have better news. 

 

As an alternative solution, maybe contact a local underpinning firm for a consultation. They may well have a cheaper solution that your SE will be happy with given their more in-depth knowledge of the situation. 

 

Good luck. 

 

 

Getting hold of planners at the moment is very difficult, and I don't think they have any sympathy for anyone, but they may agree to a new build in exactly the same footprint, one of the paths I'm going to investigate.

 

Busy weekend coming up .

 

 

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Get another SEng - cannot see any reason why you need that and the wall I expect is not actually taking the weight of the roof - it will be the steels. If not, add in a steel portal along the back of the wall. 

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The underpinning sounds OTT.  It may be easier to do a section of wall at a time - demolish, new foundations, rebuild.  There is always a danger that this will no longer be deemed PD, so don't do too much in one bite and retain / repair / reinstate as much of the steel frame as possible.

 

SEs often just spec something that will work, with little regard to the cost.  I had one spec 2 layers of A393 mesh for a ground bearing concrete slab.  When challenged they were happy with a single layer of A142.

 

Did you dig a trial pit to establish foundation depth?  Also, have Building Control been to site?  They often have a good idea of typical acceptable foundations in the area.

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2 hours ago, Mr Punter said:

The underpinning sounds OTT.  It may be easier to do a section of wall at a time - demolish, new foundations, rebuild.  There is always a danger that this will no longer be deemed PD, so don't do too much in one bite and retain / repair / reinstate as much of the steel frame as possible.

 

SEs often just spec something that will work, with little regard to the cost.  I had one spec 2 layers of A393 mesh for a ground bearing concrete slab.  When challenged they were happy with a single layer of A142.

 

Did you dig a trial pit to establish foundation depth?  Also, have Building Control been to site?  They often have a good idea of typical acceptable foundations in the area.

 

These SE's have dug 2 trial pits, one when they first inspected for planning and again before producing the above.  

This is a single block wall barn, no steel involved, but we assumed that we would need steels for the roof, but no mention of that.

 

If we do it say, room by room, will we be able to do 1m foundations, do you know.  This is our current plan / hope.

 

Also, out of interest, if we do this how do you 'join' the different foundations in a straight line.

 

No BC yet, this report was to get the architect do do BC drawings.

 

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Can you appoint a private BC without having submitted drawings, I wondered if we could progress in that direction.

 

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maybe a case for helicoil screw piles. wont save you much cost wise but speed and mess wise they are a breeze. Find a good local builder and ask them what SE they use. Yours might be one of the un-better ones.

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Would be easiest to drill holes in the foundation , resin in rebar and tie the new mesh for the new foundation into the rebar

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Hello @LSB
 

Hope this helps a bit and gives you some food for thought, even if just to help you rule things out. I have made comments / suggestions / rambling thoughts in italic in line with your text.

 

Firstly don't depair and think the worst, hard to do when you are at the sharp end.

 

I haven't posted to my blog for a couple of months, mainly because we haven't been able to progress until we got the Structural Engineers report.

This was promised in 2 weeks and ended up taking 10.

 

Hopefully they dropped you a note explaining why things were taking longer as a common courtesy.

 

I now suspect that this was because they didn't want to tell us the news.

 

Don't suspect anything at this stage keep an open mind.

 

Our build is a barn conversion so we've had to jump through lots of hoops. ,making lots of money for other people.

 

But you will have something a lot of folk would give their back teeth for.

 

But, particularly for the SE, first it was the report where they said to planning that the barn was convertible.

 

The SE may have been looking at the condition of the walls and could they be retained as  planning constraint, maybe that was their brief? Cost would not have been a significant factor.

 

Then the 1st phase ground contamination report, no issues there.

 

Good.

 

Planning approved with condition of phase 2 contamination report.

 

No significant problems  constraints with that? Any other conditions other than just getting the investigation done?

 

Then we started preparing the site, documented in previous blogs, we did this thinking that it would benefit us with the SE report to get the building regulations drawn.

 

How wrong we were.

 

Maybe not.. just by messing about on site you can gather valuable information that can be used to solve a problem.

 

One of the limitations of the barn conversion was that one side of the building can only be 2.2m high.  We worked around this by designing rooms so it wasn't needed for walking.

 

Yesterday, I received the report, only to be horrified to see that this low side of the building, 2.2m remember, needs underpinning foundations of 'at least' 2.4m.  How can a single storey build possibly need foundations deeper that the height of the building.

The opposite side is 3.15m high to the roof, here the SE say we only need 1m deep foundations, figure that out.

 

The soil is not clay, not sand, there are a few 3" elm trees that are being knocked down so no large roots.

 

From what you have said it seems like the soil is the crux of the matter. The roof loadings and the self weight of the wall are not onerous given the size of structure you have. I'm just speculating but are the walls close to a boundary with trees on the other side?  Has the SE not realised that the Elms are young and to be removed.. then speculated that they will grow into large trees? It could be a simple lack of communication!

 

Digging deeper if this is not a communication issue. You mention that the soil is neither clay nor sand. It may still bit bit expansive.. prone to swelling / shrinkage.. much depnds on which part of the UK you live in. Some of the Gault (fissured) clays in England are sensitive to ground and moisture changes, If for example you live in parts of Northern Ireland, Norfolk, Stirling in Scotland, the Severn type estuary regions in Wales then the ground can move about to a good depth.

 

Another thing is that your SE may have identified a band of silt.. so not clay or sand.. and this is another type of material. Silts are tricky to build on so maybe the SE has, luckily for you picked up on this.

 

But, it gets worse,  they say that this must be done 1m at a time, doing 1st meter, then 3rd meter, then 5th meter, then 2nd meter etc.etc.

This particular wall is 25m long.

 

They have no issues with the existing internal walls.

 

Unless you have spent say 10k plus on a pretty comprehensive ground investigation.. maybe with an interpretive report I can't see (willing to learn though) the justification for concluding that the founds can be significantly shallower for the internal wall.. which may be load bearing to some extent. This makes me lean back towards the trees rather some tricky layer of soil in the ground.

 

I've never been so glad to be stupidly busy at work to take my mind of this fiasco.

 

So, what do we do.

 

Relax! Have a chat with the SE.

 

The thoughts I have are:

 

1. Can we knock down the back wall leaving the rest and build only 1m deep like the wall on the opposite side,  but I would still need to get planning.
 

2. Do we write off all the work we've done and all the money we've spent (lots) and try and get planning to start from scratch with a kit house.  It would have to be self build though due to the extremely limited funds available.

 

3.  The long wall splits into utility, 2 x bathrooms, 3 x bedrooms and a pantry.  Do we knock down the wall for each room and then rebuild it bit by bit and with what foundations.

 

4.  Do we start on the high side of the conversion and work backwards ignoring the problem for now.

 

The sides vary from 1m front to 2m foundations at the back.

 

The most disappointment I feel is that the SE passed the building as fit to convert, including digging holes to look at the existing foundations with no mention of anything like this.

I don't know if it makes any difference, but the original SE was probably about my age, in his 50's, whereas the recent one (same firm) was barely out of nappies and didn't want to talk to us when he was here to discuss anything.

 

What I have done is:

 

a. Requested a meeting with the SE and his manager to ask why so deep and about a new wall.

If we can knock down the wall and put in 1m foundations then that is manageable as with the digger we can knock the existing one down and dig the trenches before getting a groundworks crew to do the rest.

 

b. Started compiling an email to send to the planners, but with the current situation I don't think I will hear anything.  Also, I'm a bit wary, if we say what is required can they pull our planning and still not allow us a new build.

 

c. Started looking at some kit companies who provide self build kits to get some ideas of costs.

 

The one thing that we cannot do is dig down 600mm x 2.4m a meter at a time.  Maybe a groundworks company could, but at what cost for what, in reality, is a tatty barn which, if we could have got planning we would gladly have knocked down and crushed.

 

I spoke to the planners after we got planning to ask about this route and we told that we had no chance.

 

Here's a little reminder of the layout.

 

In summary see what the SE's have to say. If you get no joy then dive back on BH. Provide as much info on the ground as you can and some cross sections so we can see where the roof loads go, the wall thickness and so on. BH members can then have a few more bits of info to work with.

 

Look forward to your next post/ blog once you have got over this bump in the road.

 

All the best.

Edited by Gus Potter
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Every SE I have ever used has massively over engineered the project - they always keep in mind that they are sticking their PI on the line with each design.

 

If you have a decent building inspector it may be sensible to dig out a section and get them to inspect and to tell you what they consider appropriate. If you are sat in decent firm clay I can't imagine they would be expecting a massive depth.

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my money is on trees being the issue as even 1.5m would be overkill on clay in the absence of trees, piling would be cheaper. 

 

 

 

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On 26/11/2021 at 08:55, Marvin said:

 2.4m deep underpinning was because the roots from a mature oak tree

 

Let me tidy a few points up. It is not a fiasco, and it would be unwise to suggest that to your Engineer.

I foresee a solution

 

1. Trees will the the issue here. 2.4m depth is normal enough if the trees are, or will be be tall, with high water demand, and the ground is liable to shrinkage.

2. Clay is the worst*. It expands and shrinks seasonally. If the ground was sandy, or the trees were pine or bushes really, the requirement would not be for 2.4m

3. The foundations are designed for the eventual heights of the trees not the current.

4. the depth is less elsewhere because it is further from the trees, and nothing to do with the building size.

 

Now,  you say the trees will be 'knocked down'. Does the Engineer know this?

 

Even if he does, the trees' effect on the ground will continue. They could grow again if the stumps remain.

For at least the next year after the trees are removed, the ground will move as the conditions have changed. the likelihood is that the ground will slowly get wetter, to many metres, and the clay will swell, and the ground will rise.

 

Discuss this with the Engineer and ask for confirmation. then don't build your foundations for a while.

 

The trees should then be removed asap, to let the winter water seep slowly into the ground (again clay is the worst for this, and will take time to wetten.

 

BTW underpinning has to be done in 1m lengths or there is no support and the wall falls down.

 

* Clay is made of millions of layers of silt washed into a lake a very long time ago. These layers allow water between them and expand. Then trees suck the water out and it shrinks again. At 2.4m down the tree does not drink the water, hence taking the foundations down to there.

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Thanks everyone for you comments and insight, here is some info to fill in some of the questions above.

1, We are in East Suffolk.

2. This is the sight, the conversion is an L shape at the top of a slope.  The house at the bottom is an existing home.

 

image.png.4ff39169da270b1c1d9cda631cf53975.png

 

3.  This is the drawings done by the SE on their first visit to check if the barn could be converted.

 

image.png.035f8f666156cf6c3b57f55e5bb22d8b.png

 

 

4. SE comments re soils for planning, this is obviously not the whole document, just a bit from it.

 

image.png.453b5476641e960b584d514a7c56563b.png

 

5,  Walls

 

image.png.4dab1228e9c8c3f6aa0f0906300bd9d7.png

 

6. Floors

 

image.png.6cba5be0f5d2332cd854fc52b9e04b4f.png

 

7. conclusion

 

image.png.e761d20bc1c9584683f0edfa3c7f713b.png

 

 

So, the first report, bits above from the SE did not raise any issues.

They do mention trees, but these have been cut down and all the roots removed except a few still waiting to be done.

 

 

This is the only remaining trees, which I will cut down if necessary, but I would like to leave a couple just to hide the electricity pole.

 

cleared_bank.thumb.jpg.39a99141afae466279e341327b15e942.jpg

 

 

The back edge was like this before we started, not a lot of trees, even then.

 

DSC_0572.thumb.JPG.1a72c4dbb4c57a4a0d57e4108a419e30.JPG

 

 

This is what it looks like now.

 

back_passage_cleared2.thumb.jpg.1d68ad722d50c6a034de9710d1491dc8.jpg

 

 

Every tree that has been removed we have dug out the roots.

We have also remove the retaining wall mentioned as we wanted more space along this side of the building.

 

The plan is to terrace the bank, eventually

20210823_191721.thumb.jpg.80a82d74a70d93b097930fa8cb2cbd95.jpg

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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I have now organised a Teams meeting at 9am on Tuesday, to ask some questions.

 

I am going to ask about foundation depths and if a new wall would reduce them.

 

I did tell the SE that all the trees will be going.

 

 

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12 minutes ago, LSB said:

I have now organised a Teams meeting at 9am on Tuesday, to ask some questions.

 

I am going to ask about foundation depths and if a new wall would reduce them.

 

I did tell the SE that all the trees will be going.

 

 

Sensible approach , if you have a preferred option just ask why cant we do this ?  

Our roof was designed by an SE the first design  was, from an engineering point of view ,amazing  a 10m span from the eaves to the ridge  supported by 1 steel beam on each side at 8m  , unfortunately from a construction and cost point of view very expensive and to quote the builder " i can do it but you can forget about one days crane hire i will need it onsite everyday until all 98 of the 9m long 2 x 9's are in place " he suggested we add 1 additional beam on each side, use 4.8m 2 x 7  timbers @ 600 centres rather than 400 . 

Put his suggestion to the SE and the reply was well you could do it that way if you want to and it might save you a bit in materials ! 

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My preferred option would be a new cavity wall as the current one is single skin, hopefully with a 1m foundation.

Hubby is not sure what he wants and would like to just pretend it isn't happening, he is the doer and I am the planner.

 

 

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Be very aware that to qualify for Class Q this must be a conversion and incorporate the existing structure, not a replacement.  This seems very stupid and petty in your case, but it is the law and from what you have mentioned your local authority would keenly enforce it.

 

I understand that new foundations are a no-no for Class Q.

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