Running Pipework in insulation under a concrete floor?

[scott2hot]

Hi all,

I've been asked to extend the plumbing into a small extension (utility room and toilet/basin). They want the pipework concealed under the floor, the builder has advised me that on top of the concrete slab there will be 75mm insulation and a 75mm screed. I plan to run plastic pipe within the insulation layer and bring copper tails up through the screed - I plan to sheath (22mm plastic pipe/ pipe lagging?)these copper tails as they come through the screed .

Would it pay to lag the plastic pipework, I will not be around when the insulation and screed go down

Many thanks for your thoughts.

 

[SimonJohns]

I've done this before. Run it on the slab. Then lay the insulation boards over the top

No need to lag. But have no joints under the floor. And pressure test. Then cap ends to prevent debris getting in

 

[stevetheplumber]

id put them in felt lagging above the insulation if its copper or unlagged if its plastic but pump them up prior to screeding as you would for underfloor heating

 

[scott2hot]

Due to the layout of the toilet and basin to the utility room i have no choice but to use a couple of elbows, - I wish I could run it in a single run but this won't be possible - definately will need to test before the floor goes down!

 

[Gray0689]

All pipework should be lagged copper and plastic and as said no plastic fittings should be under screed

 

[SimonJohns]

I would go for the unipipe system in this instance

And I would run it on the slab under the insulation. Then the need to lag will be disregarded imo

 

[scott2hot]

I was planning to T off for the toilet but I think I will run a seperate supply to it. If I use copper I can use bends instead of elbows - and then lag the pipes.

 

[Best]

I always use copper & in this case, I would cut the floor insulation out & put the pipes in with 19mm thick armaflex insulation with floor insulation in between them. This still gives at least the 75mm depth of screed. Not ideal way, but I think it best you can do. If a new house, then I prefer insulation sheets below pipes & then another fitted close to them. Lets you cross copper pipes by just cutting a little piece of bottom sheet out.