Water Pipes Under Block & Beam or Within Insulation?

7 Oct 2018
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United Kingdom

Can’t seem to get/find a definitive answer on this.... we’ve built an extension with a block and beam floor that will have the usual 100mm insulation with 65/75mm screed on top. Part of this extension will have a kitchen within it with an island that will have a sink on it. My question is running hot and cold water supplies to it?

Will it be better to run the supply pipes on top of the block and beam floor but under/within the insulation of the floor or run the pipes underneath the block and beam floor within the air gap/void? We will run these in barrier plastic pipe so joints will be at a minimum if at all.
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Yes, essential to do it within the screed. Make sure you space the hot and cold apart from each other or else you will end up with warm mains water.
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Hi there
we have a very similar project and have hot and cold water to a kitchen island sink but we will have underfloor heating in the floor screed. (make up is block and beam floor, 125mm insulation and 75mm sand and cement screed)

My plan was to run barrier pipe for the hot and Cold pipes with no joints insulted in in an insulation`tunnel' with 25mm insulation over the B&B floor first.

can anyone see any issue with that method?

Mine sit on top of the insulation, covered in tape to help protect them, and apart from each other.
Would the cold water not be warmed by the underfloor heating up the screed?
Is there UFH? OP didn't mention that.
the original post doesnt mention UFH but our install has UFH hence my proposal to run pipes in insulation as per my sketch. any thoughts anyone?
thanks in advance
ah, I see. Hmmm.
It would make some sense to keep the cold separate from the heating, but the hot can run through near. Your sketch seems sensible, so long as the H and C have insulation between them.
insulted in in an insulation`tunnel' with 25mm insulation
if there are services in the insulations, Ive found it easier to do the insulation in 2 layers. in you case say 2 x 60mm

that way you can lay down one layer with gaps where the service runs are, then do a 2nd layer at 90 degrees to stagger the joints.

plastic water pipe is a pain as its all bendy and difficult to cut around.

if you run electrics too then Ive learnt that is easier if it runs around the perimeter, then cut a rebate out of the insulation. My electrician used to run it all in copex.

Dont let the tradesmen just run services at any random angle if you can avoid it, straight lines are easier to cut the insulation around
plan was to use barrier pipe for the hot and cold supply’s so there are no joints. will make sure there is adequate insulation between the pipes. Will also have a chat with my sparks re the copex
many thanks
What you going to do for the waste from the sink in the island

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