New waste pipes in floor of extension

[fabgav]

Hi all,

just after a bit of clarification/knowledge before I contact my BI (ha's not very approachable)
I need to lay new waste through the extension floor slab.
I am not sure how is best to do this.
Do I lay the pipes at correct fall rate on 100mm bed or pea gravel, box it all in, do the rest of the floor then fill over all pipes separately?
Do I lay all mot type 1 and sand then dig out for pipe and fill with mot1 and sand again?

Or is there another way I should be doing it?

Thank you in advanced

 

[oldbutnotdead]

Got to say that's a crap piece of design.
No option to bury the pipe outside the building? Or to bury it deeper (so it isn't compromising the insulation and dpc quite as much)?
Is there a manhole outside in a straight line on the run (for rodding)?

 

[fabgav]

NO man hole in straight line.
Footings were not shuttered out to allow for the pipe to be lower - took builders advice on this and he seemed to think this was standard and acceptable.

 

[oldbutnotdead]

Builder couldn't be arsed more like. You're in the clart then- not a chance bco will sign off on an unroddable underbuilding run like that. Plus you're digging a great big thermal bridge through the insulation.
Presumably you've got walls up but no floor slab yet? Have a good read of the relevant Approved Document for foul waste to start with and come up with a scheme that gets close to 'deemed to comply'. If you end up coring through the footings, big deal- big hole, compressible material, it's all in the ADs.

EDIT If there's no manhole, how do you know what depth to run the pipe at?

 

[SGAsp]

This is me also.
The man hole is at a 90bend to it.
Would have to have a vertical drop outside underground then the turn to manhole.
I've reasonable access to the footings under the lintel at the moment could possible cut this down.
I've messaged bco, will see what he suggests.
In my heart I knew it was a crap situation.

 

[oldbutnotdead]

Well you'll need another manhole at the 90 degree bend then. If the vertical drop is a continuation of the stack pipe (don't forget rest bend) then that's fine. If it's 1:60 then vertical then 1:60 not so fine, you're unlikely to get a blockage in the vertical but very likely to get issues at the bottom of it. You might get away with a rodding point above the vertical but might not...more likely to want to rod from the foot of the vertical towards your new manhole so inclined rodding point- all very messy.