Can’t Dig Foundations

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Hi some advice please,

Anyone know of what we can put on the end of our house that doesn’t require foundations as an extra dining room/playroom?

We were hoping to extend our living space as are in desperate need of more space. We had a surveyor round who has said an extention is a no go as the foundations would need to be dug over 3 meters deep due to a sewer in our back garden. The sewer is placed just over 3 meters away from the house, so we’d either have to go over permitted develoment (which our council is unlikely to approve planning for) or only do a 2 meter extension which for the price of the deep foundations is way overpriced. Even if we move the sewer we still have the drain which we would have to build over and would still need deep foundations, at a loss really what to do. We are unable to move currently as can’t afford anything within the area that is any bigger and we dont really want to move away from the kids schools.

I was thinking of covering our patio but dont think that would be useable all year round even with a patio heater. Or maybe a summer house with a covered walkway to it?
Does anyone have any good ideas for a year round room with no need for foundations?

Or has anyone had similar which they have managed to convince the water company not to need such deep foundations?

Thanks in advance.

We had an extension built over a drain. The builders just dug around it and we then had the drain redirected.
We thought we needed a building over agreement from the water company but turns out we didn't need it

For a play room a large summer house would make a lovely den.

Or you can get retractable awnings that fit on the the wall to cover your patio.

Can't help with the foundation stuff, sorry!

3 metres deep? Is that correct, it seems jolly deep?

Could you consider a conservatory?

A conservatory doesn't need deep foundations.
But 3m does seem very deep. Are you sure they aren't using the calculations for a 2 storey extension!

Was the surveyor from the water company? What is the sewer, how big and how deep? Your water company might have the details about what is permitted in terms of build over and foundations. Thames water has full details on their website.

3m deep? I think you need a second opinion!!

Yes the drain is definitely 3 meters deep and all the information on their website and also through a brief phonecall with Thames water they say foundations must go deeper then the drain. The surveyor said it was very unusual for a residential sewer to be that deep.

We are hoping that they will say as the drain is so deep that normal foundations wont affect the pipes but so far that doesn’t look likely.

@Rollercoaster1920

Was the surveyor from the water company? What is the sewer, how big and how deep? Your water company might have the details about what is permitted in terms of build over and foundations. Thames water has full details on their website.

The surveyor was from a local company who has drawn structural plans for other houses on our street. I also called durabase’s technical line and they also agreed it would need to be below the pipe/sewer line and cant have anything built within 1 meter of the pipe or manhole, so wouldn’t be beneficial for us to do.

We’ve been looking at garden pods today but will need further information on whether they need foundations, its so frustrating every time we think we have a solution it doesn’t seem to pan out.

A caravan?

Would this still be the case of it were a timber framed/lighter extension?

Maybe some sort of semi-enclosed verandah with glass roof? Or a garden room beyond the line of the sewer. Could you have an extension build on piles rather than trench foundations?

Get a second opinion. We were given 3 definite contrasting scenarios by mansplaining wazzocks

Thanks all, will have a look into lighter frame extensions to see whether this might be feasible. We were tolded piling would not be acceptable for the water company. I will definitely get a second opinion and will also ask Thames Water to survey if possible so they can tell us directly what can be done. If not I think a garden room further away from drain is the way to go.