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Posted: Thu Jun 28, 2007 7:43 pm
by terman
Hi All
I am building an extension and have to move the foul inspection chamber to meet the building inspectors requirement.
This would put the new 150mm pipe running parrallel with the new foundation trench and very close to the new foundation trench.
The BCO has said I can use the same trench for my new trench fill foundation and the new pipe as long as the foundation is below the invert (no problem) and I shutter the drain. What is the easiest prefered way to shutter the drain from the foundation concrete' so they can both share the same trench. The Trench will be about 600mm(Foundation)+450mm(Foul Drain) wide and 1.2Meter deep
Thanks for any help
Posted: Fri Jun 29, 2007 9:33 am
by Tony McC
Sheet of plywood.
Posted: Fri Jun 29, 2007 6:29 pm
by terman
Thanks Tony 
What should I use under the drain for levelling?
Posted: Fri Jun 29, 2007 9:29 pm
by seanandruby
dig the foundation trench and shutter at 600 wide to height of concrete infill. once concrete has gone off ( next day ) dismantle shutter. then put in shingle to just below invert using pins and line for level. hope that helps?
Posted: Fri Jun 29, 2007 10:35 pm
by terman
Thanks for reply Sean
I might not have made it clear but I kneed to concrete fill the drain trench also so I was asking what I should use under the drain to set the fall whilst the concrete sets.
Posted: Sat Jun 30, 2007 9:29 am
by Dave_L
terman wrote:I might not have made it clear but I need to concrete fill the drain trench also so I was asking what I should use under the drain to set the fall whilst the concrete sets.
Surely supporting the pipe at each end where possible after setting the fall would be possible?
Posted: Sat Jun 30, 2007 12:03 pm
by Tony McC
I'm not sure if this is concrete haunching to the pipes or just concrete backfill.
If it's haunching, then the pipes are laid on concrete and covered with the same, with movement joints at critical points. If it's just concrete backfill, then the pipes are laid on A10 pipe bedding, covered with around 150mm of same, and the trench is then topped-up with lean mix.
Posted: Sat Jun 30, 2007 1:03 pm
by flowjoe
I think bco now require concrete encased pipework under buildings and anything within 1mtr.
I lay the system on bricks before replacing each brick wih a mix of concrete, this ensures the system is at the correct level and that it doesn`t get knocked about when we have the big pour. Plastic pipework tends to float if not anchored down when the concrete is poured.
Posted: Sat Jun 30, 2007 5:42 pm
by seanandruby
what pipe are you using? there are a lot of different methods for levelling. you need 100 to 150 surround. place your base about 100ml below invert. put plinths of concrete at required level and lay pipes. place movement joints at every collar then concrete half bore so building inspector can check them, then top up whilst concrete is still live. alternative place on bricks with expansion joint between brick and pipe, incase you cant get bricks out. other way concrete to just below invert lay pipes and channel out for expansion. it all depends on how much you have to lay really. good luck
Posted: Sat Jun 30, 2007 8:16 pm
by terman
Hi Thanks Guys some great advice
The Extension length is about 13ft the pipework running in parrallel will be in plastic 150mm. I believe I am required to encase in concrete since the pipe work is only 161mm from foundation trench (<1meter).
What do you typically use for the expansion joints between brick and pipe?
Is it essential that the shuttering ply is removed as I was hoping to pour both foudation trench and drain at the same time?
Posted: Sat Jun 30, 2007 10:50 pm
by seanandruby
(What do you typically use for the expansion joints between brick and pipe?) ..... "Fibreboard." the expansion/movement joint goes around the collar 150 to tally with the concrete surround.
i only put it on top of a brick if its used for levelling to avoid pressure on the pipe. its not good building practice to leave shuttering in, although it is sometimes unavoidable below ground..in your case i wouldnt imagine it will do any harm.