Build over agreement - Drain survey completed and not sure what to do now

[vcsush]

Hi All

Thanks for any help up front. I am looking to purchase a house which has a manhole inside of 3m, where I am planning a rear extension. I did a drain survey and it isn't really any clearer how I move forward to understand questions like

1. What is the probability of getting an ok from TW for a build over?
2. Do I need to move the manhole MH1? Do I need to move the public sewer along with that? What does that do to the lateral drains?
3. Can I eliminate MH1 and redirect the lateral drains straight to either OF1 or MH2?

Do I need to engage an architect next in order to get the answers to these questions and understand what other possibilities might be there to get an ok from TW?

Any help on who I can talk to next or what steps I can take to make the TW extension permission probability any clearer would be much appreciated. I have included the diagram from the drain survey (me being a FTB it isn't exactly very clear).

Thanks

 

[Murdochcat]

Best you call TW. They have a team that deals with this stuff and in my experience they are very helpful

 

[noseall]

Hi All

Thanks for any help up front. I am looking to purchase a house which has a manhole inside of 3m, where I am planning a rear extension. I did a drain survey and it isn't really any clearer how I move forward to understand questions like

1. What is the probability of getting an ok from TW for a build over?
2. Do I need to move the manhole MH1? Do I need to move the public sewer along with that? What does that do to the lateral drains?
3. Can I eliminate MH1 and redirect the lateral drains straight to either OF1 or MH2?

Do I need to engage an architect next in order to get the answers to these questions and understand what other possibilities might be there to get an ok from TW?

Any help on who I can talk to next or what steps I can take to make the TW extension permission probability any clearer would be much appreciated. I have included the diagram from the drain survey (me being a FTB it isn't exactly very clear).

Thanks
View attachment 346394

2.36m deep?
Those drains (and extension) are going to be a handful!

 

[vcsush]

Best you call TW. They have a team that deals with this stuff and in my experience they are very helpful

Thank you. I tried that already but they weren't much help. Just pointed me to their Build over section. To be fair, I can't really blame them.

 

[freddiemercurystwin]

I don't understand the drain layout, where the existing house is and where the extension will go. Perhaps do a sketch over the estate agents plan showing what's what ...

 

[vcsush]

I don't understand the drain layout, where the existing house is and where the extension will go. Perhaps do a sketch over the estate agents plan showing what's what ...

Here it is. Apologies, for the crude drawing. The yellow bit is the terraced house and the blue bit is where the extension will go.

 

[freddiemercurystwin]

Bloody hell, so the dark grey above and below is each adjacent terrace? This is a full width rear extension? Assuming this is a shared sewer running through the back gardens and taking the waste from all of the houses TW or Building Control won't permit a manhole inside the extension, so you'll need to relocate any existing manholes to outside of the extension, with a full width extension it's hard to see how that can be achieved without digging up the neighbours gardens.

 

[vcsush]

Bloody hell, so the dark grey above and below is each adjacent terrace? This is a full width rear extension? Assuming this is a shared sewer running through the back gardens and taking the waste from all of the houses TW or Building Control won't permit a manhole inside the extension, so you'll need to relocate any existing manholes to outside of the extension, with a full width extension it's hard to see how that can be achieved without digging up the neighbours gardens.

Thank you for the reply. That is correct. This is terraced and the dark ones are adjacent terraces, and that is a shared waste sewer running through the back garden. Also agree that manholes inside the extension will not be permitted. I don't think I can relocate the manhole to the neighbours' as they seem to be building a 3m extension as well (I am not entirely clear what they are doing with their sewer / manhole...this is something I am trying to find out).

Any thoughts on if I can eliminate the manhole completely? From what I understand there needs to be some access to provide "rodding" ability. Is there another way of doing this?

The only other way I can think about is to move the manhole to one end near the fence and build the extension around it....like the pic. Any thoughts on that?

Thank you in any case for your reply. I appreciate it.

 

[freddiemercurystwin]

You would need to fit the manhole on the opposite side as it needs to be on the downstream, your existing FWG1 & SVP-1 need to connect into it.

 

[vcsush]

You would need to fit the manhole on the opposite side as it needs to be on the downstream, your existing FWG1 & SVP-1 need to connect into it.

Understood. Thank you for the input. Two more questions if I may. Downstream the sewer runs into something called OF-1. As per the drain survey report, OF-1 node is "Major connection without a manhole".

1. Could I connect FWG1 and SVP-1 straight to OF-1, without a manhole?
2. Since OF-1 is apparently without a manhole, will there be a problem if a manhole is shifted to the opp end in the pic above (near OF-1)?

Not sure if you would be able to answer these questions or not. But, in any case, thank you again.

 

[jono_h]

See if Thames Water have a handy guide to help.

This is a picture from the Welsh Water equivalent, with which I’m too familar!, but broadly if your neighbours have full width extensions they wouldn’t give permission for another full width extension and would expect space to be left for an inspection chamber.

 

[noseall]

Here it is. Apologies, for the crude drawing. The yellow bit is the terraced house and the blue bit is where the extension will go.

Are those numbers drain depths? I.e. 2.36m deep? If so why does the drain depth decrease further downstream....

If the drains are 2.36m deep - move house.

 

[vcsush]

Are those numbers drain depths? I.e. 2.36m deep? If so why does the drain depth decrease further downstream....

If the drains are 2.36m deep - move house.

The 2.36 is length of the section as I understand it. Depth is 1.13m.

 

[noseall]

Depth is 1.13m.

Manageable.
New footings will be around 1.2m