Build Over Agreement - Thames Water

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Hi all,

I was hoping for some advice before I cry into a pillow later on!

I want to caveat the whole story by saying both my wife and I are not at all knowledgeable about plans, building etc, although over the last couple of weeks I have become more au-fait.

We did a single storey extension back 2019/2020. It finished during the whole pandemic.

For some reason unknown to us, Building Control (private company) stopped coming to the property in 2020 I presume it was a mixture of the builder not calling them and lockdown. 2.5 years down the line we received an email from Building Control saying that they have not visited the property for a while and need to come out to do the final checks. I found this weird, as they would normally communicate with the building company, so I said sure no problem.

It transpires that our builders did not follow the architectural plans for the drainage. Essentially, there was a manhole in our garden that was built over and new one should have been created outside the extension in the garden using something called a "Y" connection. What's strange is that we have Build Over Agreement for the manhole we have built over so not too sure why they then did not create the new manhole and connect it.

I still speak to the actual site manager who was responsible for the work (he is no longer with the building company that did the work - long story), although we do not speak to the owner of the building company (he was an awful person); he says that drain was not in use and was blocked, and they redirected the pipes directly to alleyway, which then goes out through our drive (where there is a manhole) to the public sewer; to which I replied why didn't you consult me or the architect about making such a change? He did not have an answer.

I have just looked at our Regulated Drainage and Water Search report we got when we bought the house in 2014 and it included a Public Sewer and Water Map. The maps shows that there are NO Public Foul Sewer, Public Surface Water Sewer and Water Pipes in the boundaries of our property. I also spoke to both neighbours, and they also confirmed we have no shared drains in our garden. We are a detached property if this makes any difference.

in the Regulated Drainage and Water Search report there is also this question "Does the public sewer map indicate any public sewers, disposal main or lateral drain with the boundaries of the property?"

Answer "The public sewer map indicates that there are NO public sewers, disposal mains or lateral drains within the boundaries of the property". There is also a "please note" after that basically says there may be one but not on the map, as record keeping may not be great (I am paraphrasing here).

There is also another question about sewers and lateral drains serving the property being the subject of adoption agreement or application. The answer again was a NO.

Out of curiosity, did I actually need a Build Over Agreement? Bit late now as I already got one, but good to know.

Does anybody have any advice? I am truly sorry for the long write up, but I cannot sleep and really worried that they may ask to destroy my extension or cause issues with my re-mortgage in 2 years' time.

Thank you all for any help you provide or just for taking the time to read through this mess of a post!

KJJ
 
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The maps shows that there are NO Public Foul Sewer, Public Surface Water Sewer and Water Pipes in the boundaries of our property. I also spoke to both neighbours, and they also confirmed we have no shared drains in our garden. We are a detached property if this makes any difference.
Not an expert.

If the foul drain starts at your house, and is not shared, e.g., you don't take else's waste, I think it's private up to the boundary where it either joins other foul drains or is connected to a sewer.

My limited understanding then is no, you didn't need a build over.


However I could be wrong
 
Sounds like this scenario below from Thames Water guidance. You really need to look at the building plans and confirm where your drains run and whether they are shared, the official sewer maps rarely show minor shared drains. I doubt Thames Water would have gone through the Build Over process if it wasn't a shared drain.
If the builder has changed what is shown on the approved plan it is up to them to provide you with details of the "as built" drainage layout so you can get that checked.
build over manhole.jpg
 
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Sewer maps are not always entirely accurate and can't be 100% relied on, and neither can opinions of neighbours. The only way to be sure is to produce a plan of ALL sewers, drains and connections including directions of flow. If you do this and no drains cross the boundary at any point, your drains are most likely private and you can build over them. If any drains/sewers are public, you will need permission to build over. Sewer authorities don't allow building over manholes. My advice is produce a plan and take it from there.
 
Not an expert.

If the foul drain starts at your house, and is not shared, e.g., you don't take else's waste, I think it's private up to the boundary where it either joins other foul drains or is connected to a sewer.

My limited understanding then is no, you didn't need a build over.


However I could be wrong
Thanks, Jacko.
 
Sounds like this scenario below from Thames Water guidance. You really need to look at the building plans and confirm where your drains run and whether they are shared, the official sewer maps rarely show minor shared drains. I doubt Thames Water would have gone through the Build Over process if it wasn't a shared drain.
If the builder has changed what is shown on the approved plan it is up to them to provide you with details of the "as built" drainage layout so you can get that checked.
View attachment 285262
Thank you. They will provide plans, so fingers crossed.

Would Thames Water use their powers to destroy my extension, or will they allow me to keep it up until there is a need to dig up the floor? Will BC certify me?
 
Sewer maps are not always entirely accurate and can't be 100% relied on, and neither can opinions of neighbours. The only way to be sure is to produce a plan of ALL sewers, drains and connections including directions of flow. If you do this and no drains cross the boundary at any point, your drains are most likely private and you can build over them. If any drains/sewers are public, you will need permission to build over. Sewer authorities don't allow building over manholes. My advice is produce a plan and take it from there.
Thank you.
 
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