Building over sewers/drainage.

muddyl

Evening all.

I wondered if anyone would like to give their input on this please as after searching the internet, the contradicting information is making matters worse.

A little long winded but background info will be needed i think.

I intend to build a 3 meter by 4 meter conservatory over the coming months.

I will need to build over an existing drainage system.

The pipe is approximately 1 meter below ground surface level and runs parallel to the existing building at a distance of approx 1 meter from the rear of the building.
I believe it to be a class 1 160mm pipe and would have a 3 meter run under the conservatory.
There will be no inspection covers to worry about.

The conservatory will have dwarf so i will be doing strip founds for the build. This is on clay soil so may have to go quite deep but wont know exactly how deep until I start digging.

Here is the issue I am confused over.
I intend to do strip found for the dwarf walls and then use blocks to just below ground level as I believe this will work out cheaper than deep fill concrete.
I know the drainage needs to be shuttered off and surrounded by gravel.
But im not sure bout lintels as I do not think this would constitute a load baring wall.
If I have to dig a lot lower below the drainage I was thinking of concrete strip then build up with blocks and a lintel over and continue with blocks.
If its not much below the drainage i could lintel straight on top of the concrete or perhaps use rebar over that section to make one complete concrete section.

From those in the know, what are your thoughts please?

southcoastrgi

is it a public sewer ie more than one house using it ? If so you need to speak to your local water authourity, you have to get their permission & if they say no then you can't build over it

victor2

As above. If it's a sewer public sewer (ie. shared by you and a neighbour) that you are going to build over, then you need the water authority's permission to proceed. Did this with an extension a little while back - our water authority is Severn Trent. We had to get a camera survey of the pipe before the work to get permission to proceed, and after the work to prove that no damage was done. The pipe was about a meter down and the builder had to dig under it and box it in before the concrete was poured in, so that the foundations didn't go near the pipe.
Our builder, and the independent camera inspection guy, said you cannot have foundations going only above the pipe, no matter how deep it is. The camera guy had seen one two meters down, and still the builder had to dig the foundation trench under it.

Of course, it it's a private drain, serving only your house, you can do what you like, and are comfortable with. If it fails, it's your problem and not the water authority.

muddyl

Thanks for the replies.

It is a public sewer. It will not need a camera inspection (been in touch to check) just need to put in an application for approval.

For this application, I need to know which way im going to do it first.

victor2

muddyl wrote: »

Thanks for the replies.

It is a public sewer. It will not need a camera inspection (been in touch to check) just need to put in an application for approval.

For this application, I need to know which way im going to do it first.

In our experience, the water authority have no idea where the sewers run, and responsibility for them has just been dumped upon them. So they figure they can get homeowners who want to extend their property to do the research for them, at the homeowners cost...
It may be no problem with a conservatory anyway. Both I and our builder spoke to the water authority before the work was done and we were told just to submit an application without a camera survey, just do one after the work. We did decide to have a camera survey first though, just to be sure there was no existing damage to the sewer. After we sent the application form in (without the survey report), the water authority wrote back to say we needed to have a camera survey before AND after the work. Our builder also said the council, when you apply for building regulations approval, notify the water authority if there is a sewer nearby.
It was a pain and a little expensive, but we did get the water authority's final approval letter after the work was done, which will go with the property deeds, and probably never be required ever again...

jackyann

I would talk to both the building inspector (good overall view and experienced) and the water authority (who in my experience are a bit more bureaucratic) You will need contact with both anyway, but do allow plenty of time for dealing with the water authority (ours took 2 months to rubber-stamp!)

Dan-Dan

muddyl wrote: »

Here is the issue I am confused over.
I intend to do strip found for the dwarf walls and then use blocks to just below ground level as I believe this will work out cheaper than deep fill concrete.
I know the drainage needs to be shuttered off and surrounded by gravel.
But im not sure bout lintels as I do not think this would constitute a load baring wall.

Those glass roofs are damn heavy , as are the double glazed windows?

littlerock

We had to have a camera survey as no one knew where the sewers. They put the device down the pipe and after it had travelled around 200 yards into the distance under various neighbours' gardens, they all gave up on that idea.

John_Pierpoint

victor2 wrote: »

In our experience, the water authority have no idea where the sewers run, and responsibility for them has just been dumped upon them. So they figure they can get homeowners who want to extend their property to do the research for them, at the homeowners cost...
It may be no problem with a conservatory anyway. Both I and our builder spoke to the water authority before the work was done and we were told just to submit an application without a camera survey, just do one after the work. We did decide to have a camera survey first though, just to be sure there was no existing damage to the sewer. After we sent the application form in (without the survey report), the water authority wrote back to say we needed to have a camera survey before AND after the work. Our builder also said the council, when you apply for building regulations approval, notify the water authority if there is a sewer nearby.
It was a pain and a little expensive, but we did get the water authority's final approval letter after the work was done, which will go with the property deeds, and probably never be required ever again...

A relative of mine is toying with a very similar situation:
One of those sort after out of town villages, however there is a small cluster of between the wars semi detached council houses. About 2/3rds of these are now private.
The kitchen is a typical galley style of the period.

The bathrooms and kitchens are at the rear, so it made sense for the council to run what was their private sewer along the back of the houses. They made sure to define in the deeds.that any work done to this sewer would be evenly apportioned over all the homes involved.

Presumably now the local water authority has taken over the council's responsibility for this sewer ?!

The house is crying out for a nice big, permitted development kitchen diner extension in the back garden, bridging the sewer.

It was a pain and a little expensive, but we did get the water authority's final approval letter after the work was done, which will go with the property deeds, and probably never be required ever again.

What sort of money is "expensive" ?

Furts

John_Pierpoint wrote: »

What sort of money is "expensive" ?

This cost will need to be weighed against the cost of diverting the drain around the proposed kitchen.

Building over the drain is bad practice and does raise an observation. Building Control may not allow this even if the Water Authority are not bothered. This is my experience, but others may have different experiences.

John_Pierpoint

Trying to build round the proposed extension might prove problematical as there is probably not enough fall for the detour..

I have agreed to go along to the second viewing on Sunday, so I will know a bit more about it then.

[I know what you mean - back in 2006 I was asked vy another relative to take a look at an Edwardian semi that had been built at the top of a hill in the corner of a field. Then in the 1930s the whole length of the field had been filled in with bungalows up to the pair of semis. The private sewer ran through a dozen back gardens before reaching the sewer in the more main road and half of them had extended over the line of the sewer.

One of several reasons for not buying it was the sewer arrangements.

"It does not matter what the deeds say, if that gets blocked at the bottom of the hill, there is going to be a dogs' breakfast trying to agree who repairs it and who pays".

I expect that is why the government has dumped the problem onto the sewage company.]