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Services below sub base


Field_of_Dreams
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Hi All,

 

Just starting to dig out the hole in the ground ready for the sub base that will end up supporting my insulated raft and I am hoping someone can help get something clear in my head regarding the services.

I will have water/Electrics/waste water entering/exiting near the corner of the raft and those services will be under the sub base (buried in the dirt/ragstone). I think I have it clear in my head but was hoping to get some pictures from others just so I can compare and maybe see anything that may raise some questions before it is too late 🙂 All the pictures I see in my searches are after insulated tub in in place and I was hoping to see it before that and the sub-base went in.

 

So far my plan is to run the soil pipe just below the sub base and into an inspection cover from where it will go the sewage treatment plant.

The plan for the electric's is some piping, below the sub base, that I can later pull the mains feed through...not sure what size pipe yet?

The plan for the water is also some larger piping, below the sub base, that will allow the water pipe to be pulled through.

 

Am I on the right track?

Pictures of previous work similar to mine would be most appreciated so I can know if I am on the right or wrong track.

 

Any help or guidance, truly appreciated.

 

Thanks 

 

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24 minutes ago, Field_of_Dreams said:

The plan for the electric's is some piping, below the sub base, that I can later pull the mains feed through...not sure what size pipe yet?


Use the correct 63mm corrugated ducting, min 450mm deep and make the bend up to the surface long and slow. assume you’re planning a meter somewhere else then as you can’t install an internal location for the DNO service head..?

 

26 minutes ago, Field_of_Dreams said:

The plan for the water is also some larger piping, below the sub base, that will allow the water pipe to be pulled through.


110mm water pipe with a long slow bend, min 750mm deep. Can use 63mm blue twin wall but it’s a pig getting 25mm MDPE through it. 

 

27 minutes ago, Field_of_Dreams said:

So far my plan is to run the soil pipe just below the sub base and into an inspection cover from where it will go the sewage treatment plant.


Single stack or multiple stacks ..? Best running across the base full width for this and putting a rodding point at the far end - drop into the run using Y branch with a rest bend. 
 

 

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my floor build-up is slightly different from yours - concrete, insulation, concrete, rather than insulation then concrete.  But I ran all the cold water to the different rooms, from a manifold below the insulation.  Water is always cool, great for drinking.  Building regs say the pipes have to be removable so I used pert-al-pert in conduit.  So far no issues.

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Here are some details for the SVP from my foundation detail. 

 

Also a site photo.
 

All of the services were in 110mm coloured ducting under the sub base in trenches in the ground about 900mm deep. We laid the insulated ASHP pipe in the MOT layer.  Our build up was 300mm MOT type 3, with 50mm of sand, then 300mm EPS, then 150mm concrete. 
 

My groundworks guys were very clear on what was needed. We had some 63mm ducting for electrical cabling leaving the house to the Sewage Treatment Plant that was cut into the EPS layer as per the foundation design. 110mm ducting may be overkill for the mains electric but that is what they used. We also had services leaving the house to supply water, electric and data to the garage. 

 

image.png

image.jpeg

Edited by Nick Laslett
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50 minutes ago, PeterW said:


Use the correct 63mm corrugated ducting, min 450mm deep and make the bend up to the surface long and slow. assume you’re planning a meter somewhere else then as you can’t install an internal location for the DNO service head..?

 


110mm water pipe with a long slow bend, min 750mm deep. Can use 63mm blue twin wall but it’s a pig getting 25mm MDPE through it. 

 


Single stack or multiple stacks ..? Best running across the base full width for this and putting a rodding point at the far end - drop into the run using Y branch with a rest bend. 
 

 

Thanks for the info Peter. 

 

The building is actually a "workshop" in the garden of the main property but I am trying to future proof it in case I need it to be something else in the future.

 

The electrics will come from the house via an armoured cable.

Good to know about the 63mm blue twin wall being a pain. Thanks.

Single stack for the toilet etc. Not sure what you mean by "running across full width". The distance from the buildings soil pipe to the IC is no more than 5 meters so I assume I can rod from the IC back to the building if I need to?

Forgot to say, I will also be needing a pipe for the Fibre too.

 

Thanks again for the tips and info. Much appreciated.

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My ground works crew had never done an insulated raft, so we did encounter one problem. The Surveyor did the setting out and put in all the pegs to marks the SVP pipes, etc, before the ground workers did their excavations, which disturbed all the pegs. We had to have the Surveyor come back and set out a second time. For an insulated foundation you need to cut out a flat platform for the foundations and then get the setting out done.

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@Nick Laslett Thanks for the pictures Nick...it really helps makes thing clearer in my head.

I have about 550mm of MOT and a similar amount of insulation so I am about 875mm below DPC...the thought of going even deeper for the services is the bit I am having a hard time getting my head around 🙂 

I was told not to run any pipes in the MOT as when it gets compacted, it can potentially cause damage. I guess that only applies to the solid pipes rather than the twin wall ones you show in the pictures? 

 

Thanks again for taking the time to post the pictures and all the info...truly appreciated.

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7 minutes ago, Nick Laslett said:

My ground works crew had never done an insulated raft, so we did encounter one problem. The Surveyor did the setting out and put in all the pegs to marks the SVP pipes, etc, before the ground workers did their excavations, which disturbed all the pegs. We had to have the Surveyor come back and set out a second time. For an insulated foundation you need to cut out a flat platform for the foundations and then get the setting out done.

The site was marked out by the surveyor and like you, the groundworks were going to disturb them. I added more marker pegs much further out before the ground works started so I should be good...unless I hit one with the digger which is highly likely! 🙂

As the workshop is open plan I have some flexibility as to where the services are located. "In the corner" is good enough...but I hope I dont end up regretting that at a much later date.

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23 minutes ago, Field_of_Dreams said:

@Nick Laslett Thanks for the pictures Nick...it really helps makes thing clearer in my head.

I have about 550mm of MOT and a similar amount of insulation so I am about 875mm below DPC...the thought of going even deeper for the services is the bit I am having a hard time getting my head around 🙂 

I was told not to run any pipes in the MOT as when it gets compacted, it can potentially cause damage. I guess that only applies to the solid pipes rather than the twin wall ones you show in the pictures? 

 

Thanks again for taking the time to post the pictures and all the info...truly appreciated.

 

I believe that the 110mm corrugated twin walled ducting can take a lot of weight. The spec sheet says 450N. I don't know what that means, but my ground workers did not seem that worried. The ducting was under the MOT.

 

https://unitedcivilssupplies.co.uk/wp-content/uploads/2020/03/naylor-ducting-coil-data-sheet.pdf

 

Here is the roller they used, I think it was 1.5 tonne. I think the vibration is the most important aspect of the roller not the actual weight. The Structural Engineer gave the following instruction:

 

"Ride-On" vibrating roller - max layer depth = 150mm

"Walk behind" vibrating roller - max layer depth = 100mm

 

So they had to roller the MOT at 150mm, then add the 2nd 150mm layer and roll again.

 

 

6667.jpg

Edited by Nick Laslett
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@Nick Laslett thanks for the extra info.

I see with the twin wall ducting you dont appear to have any "string lines" in them to help pull through the relevant cables/pipes. Did you run into any trouble getting the services through them?

Im not even sure how you would get the line through them anyway considering the length of the runs...maybe there is a little trick?

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9 hours ago, Field_of_Dreams said:

@Nick Laslett thanks for the extra info.

I see with the twin wall ducting you dont appear to have any "string lines" in them to help pull through the relevant cables/pipes. Did you run into any trouble getting the services through them?

Im not even sure how you would get the line through them anyway considering the length of the runs...maybe there is a little trick?

 
The 63mm ducting has string lines. 
 

The trick: Plastic bag and an air blower. Tie string to bag and use it a bit like a parachute. The air blower doesn’t even need to be that powerful. 
 

We used this in blower mode:


https://makitauk.com/product/dvc750lz


Here is an example using a Henry to suck the bag down the duct. 
 

 

 

 

Edited by Nick Laslett
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@Nick Laslett Is your twin wall all running in the same trench at the same depth like it appears in the picture?

Im just trying to get my head around the different services and the different depths they are meant to be at but it would be so much easier if they could all be at the same depth and in the same trench. I am specifically talking about Electrics/Water/Fibre.

 

Thanks

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