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Hi, Im Ivan and i'm building a house in Caterham, Surrey and have about a Million questions ;)


Ivan_England

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Hi, Im Ivan and i'm building a house in Caterham, Surrey and have about a Million questions ;). Firstly i'm struggling to get anyone to do the drainage calculations for my new build project. The architect has said they don't do it, and the Structural Engineer says the same. Then when i speak to the larger companies they don't seem interested as it's too small a project. Any advice would be great. Thanks

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Welcome to the forum!

 

What types of drainage calculations? SUDS discharge rates? Falls and IC positions for drain runs? Something else? The reason I ask is that I have some helpful advice if it relates in any way to a flat roof, which it probably doesn't.

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Normally your Architect will do you a drainage drawing to satisfy building control 

Showing drainage runs and treatment plant location 

No falls or any really detail 

I did a quick sketch and our Architect put it into a drawing 

 

If it’s more case of you needing something for your groundwork’s 

They rarely follow a drawing 

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So the house is 2.5 metres below street level where the sewer is. So we need someone to do a drainage plan to show where they run, what depth they have to be, where the manwholes need to go, and then to give me something to send to Thames Water to show we don't need a build over agreement. We also have a surface water tank that requires an overflow to run back into the main system, so need to know if i can run that into the same pump that is pumping up the foul water. 

 

Next is who can i get to do my roof design as the Structural Engineer doesn't do that either :)

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6 minutes ago, Ivan_England said:

So the house is 2.5 metres below street level where the sewer is. So we need someone to do a drainage plan to show where they run, what depth they have to be, where the manwholes need to go, and then to give me something to send to Thames Water to show we don't need a build over agreement. We also have a surface water tank that requires an overflow to run back into the main system, so need to know if i can run that into the same pump that is pumping up the foul water. 

 

Next is who can i get to do my roof design as the Structural Engineer doesn't do that either :)

Forget Architects 

SE 

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5 hours ago, Ivan_England said:

So the house is 2.5 metres below street level where the sewer is. So we need someone to do a drainage plan to show where they run, what depth they have to be, where the manwholes need to go, and then to give me something to send to Thames Water to show we don't need a build over agreement. We also have a surface water tank that requires an overflow to run back into the main system, so need to know if i can run that into the same pump that is pumping up the foul water. 

 

Most water companies try and keep foul and surface water separate. Looks like Thames are heading that way...

 

https://www.thames21.org.uk/combined-sewer-systems/

 

So you might not be allowed to connect you surface water tank overflow to the foul sewer. If that's the case you will have to look at soakaways or perhaps find a surface water drain/ditch to discharge into.

 

If you are allowed to put surface water into the foul sewer I can't see why one pump can't  do both. It would probably have to be sized for the higher flow rate of the surface water.

 

 

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Typically the architect will design the shape of the roof with some thought on how it will be constructed. Then if necessary the SE will design any steel beams needed. For example a house with rooms in the roof may need a structural ridge beam instead of just a ridge board. 

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6 hours ago, Ivan_England said:

Hi, Im Ivan and i'm building a house in Caterham, Surrey and have about a Million questions ;). Firstly i'm struggling to get anyone to do the drainage calculations for my new build project. The architect has said they don't do it, and the Structural Engineer says the same. Then when i speak to the larger companies they don't seem interested as it's too small a project. Any advice would be great. Thanks

 

What stage are you at and what have you hired the Architect to do?

 

Have you hired the Architect to get Building Control Approval for you or just some produce drawings that can be used to get Building Control Approval? In other words who is managing the process of getting Building Control Approval?

 

Typically if you hire the Architect to "get Building Control Approval" he may suggest you hire an SE or other professional to help BUT it should be his responsibility to find them and manage the process.

 

Pretty sure most architects can put together a drainage plan for Building Control even if your builder decides later it can be done a better way.

 

 

 

 

 

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  • 4 weeks later...

Hi, thanks for this. I employed an Architectural Technician to do the plans for planning permission, and then to help with building control, though he said he doesn't do drainage. I have got everything sorted now with the exception of the build over agreement with Thames Water. I spoke to Thames Water and they said that they only have a combined sewer in our road, and didn't require anything else to be put in. But the council wanted a SUDs system. Therefore we are going to get a Rainwater harvesting tank for Storm surge that then has an ultra low discharge back into the drainage system. The council have signed this off for our planning condition. Sadly a Soakaway is not an option as the ground is clay.  I basically need someone that can help with the build-over agreement and at the same time do drawings for the ground-workers to use for construction. It requires a pump, calculations have been done by the people providing the pump, but I still need someone that knows where we should run the drainage and how we can connect to the sewer, as the invert level is 3 metres underground. Any advice greatly appreciated. 

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Have you had a soak away test done? Where they dig the pit fill it water. Reason for asking is becuase I'm up in Sanderstead (no exactly far) and granted the ground is solid clay here which makes a brillant pond but poor lawn. But, parts of Caterham and alot of Whytleaf are on chalk, which would make for a good soak away. Not sure if you've broken ground yet or not, which would be a good sign of things, especially lately with the rain.

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