Underfloor insulation in bathroom floor

Owing to a leak in our first-floor bathroom we have had to take up the whole floor.
The joists are currently exposed showing all the electrics and piping which runs in floor.
I’m wondering, is it safe to insulate under the floor there with so many services running through that area.
We have some spare sheepwool insulation we could use there.

Any advice is greatly appreciated.

You can safely embed pipes in insulation. Wiring can be another issue as the wires can get warm, particularly if you use more power for longer periods than the original designer anticipated. Embedded wires have less heat dissipation and can get a lot hotter. Take the opportunity to check the wiring for damage and for grade. If necessary replace the wires with enough slack to rest on the ceiling below and suitable core size.
When insulating have the wires either above or below the insulation so that they can loose heat from one side. If embedding is unavoidable use sections of generously sized conduit so that air can circulate around the wires.

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I’ve been reading a little more about insulating the floor, knowing the smaller details count very much when it comes to insulation.
In the following article, mould prevention through control of moisture is mentioned by vapour control layer. This has thrown me with the pipe situation in our floor.
Also the mention of mould has me questioning which type of insulation?

Our plumber also seems very anti insulation for our bathroom floor under the plumbing. He says if we get a leak, the insulation will soak it up and we won’t know we have a leak, until it’s potentially quite bad. :roll_eyes:
I can see why he’d say this, but I’m at odds with it because if a leak is bad enough it will come through the insulation anyway.
In opposition, with regards to moisture - if we let the heat from the pipes flow freely into the cold bathroom floor, it’s a great environment for moisture to build up - so the pipes should at least be lagged to prevent the heat from them hitting the cold air in the floor.


This is our floor situation - you can see it’s like spaghetti junction in one part. The back wall where the toilet is situated , is the cold uninsulated gable end wall.

Plumbers hate insulation. It gets in their way. However he does have a point and I would suggest free draining insulation such as polystyrene beads.

It could be claimed that totally free draining insulation, being also vapour open doesn’t need a vapour barrier. The barrier, if used, needs to be on the warm side of the insulation. I would guess that between storeys that will be variable, depending on room use, unless one of the rooms is a designated cold room or garage, which isn’t the case here.

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Polystyrene beads ? …Is that the kind which goes inside bean bags?

Strangely, yes.
If you get it from an insulation merchant you can get it graphitised for a better U value.

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For our bathroom, we insulated the pipes, particularly the cold as you will have cold (external temperature or less) in a warm space (repeated toilet flush) and this can get condensation formation in a warm house. We did not use a membrane barrier as your floor covering will be waterproof. The room periphery was insulated- particularly the external walls- where we did use a barrier. Insulation used was rockwool , mineral wool in the floor perimeter and wood fibre in the walls. Hope this helps.

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At the least, I’m thinking to insulate the bare brick of the exterior wall - which is exposed below the tiles under the floor. We have some spare celotex we can cut to wedge in there.
I want to lag the pipes too.

The floor went down today. I’m grateful for this, but experienced a very closed mindset from the plumber who said ’ you’ll be wastin yer money girl!!’ :roll_eyes::grimacing: grrrr…

My mindset was one of toleration… I just kept thinking to myself - when you’re gone I’m going to unscrew that marine ply and insulate my floor!!

Another thing that’s not escaped my attention is the overall old school attitude of builders, plumbers , electricians … They’re often not interested in anything different to what they know.
And sexism is evident too … Trying to discuss retrofit is one thing, trying to discuss it as a woman is sometimes very testing.
I’m happy to say I haven’t experienced that here :pray:

I mostly agree. Established processes and no desire to think through alternative solutions.

I was fortunate to find a builder who was keen to learn and improve his product. We worked together for a few years before he died too early.

I haven’t found anyone willing to take up the challenge.

Hopefully, we’ll start to experience a new wave of tradesmen very soon… :pray:

I realised early on there is a shortage of knowledgable retrofit builders. Anyone ‘qualified’ seems to be bombed out with work - very much in demand!
One experience was of a retrofitter who seemed to have his finger in so many retrofit pies, he could barely keep up with demand. It caused me to make a u turn I was grateful for in the end.

Unfortunately there is such a demand for tradespeople that most have plenty of work, so there is little incentive for them to train in new techniques. If they have to pay, or even take unpaid time off, to get the training then that is a disincentive.