Laying Floor Insulation

[GSD4ME]

Dear all

We are having a property renovated and the next stage is being worked upon.
We have plumbers installing the "first fix" pipework (ie the pipes that take the hot and cold supplies from the Raeburn to the radiators, showers and sinks), the pipework being laid on the concrete floor base. These pipes are fixed down and in some cases cross over each other to reach some areas.

After they have finished, we need to lay down the floor insulation ("Jablite") which we have had delivered, a sort of expanded polystyrene. On top of this insulation will be laid the DPM and then the concrete flooring screed. Our builders have said that this is an easy job and that we should do it ourselves rather than pay for them to do it, as they are busy on other simultaneous projects.

My question is: when we lay the Jablite, do we need to cut grooves into it so that the pipes fit in the groove? My worries are that the weight of the Jablite and DPM and screed will add weight (thus stress) to the piping, thus allowing the possibility of any future leaks, which would mean lifting the whole floor again to repor these. Also as the pipes cross over each other in places, the insulation will not be completely level unless we allow for this, by cutting the insulation to fit the contours and 'flow' of the pipework.

Any advice is welcomed.

[The Builder]

It could be said that, where pipes cross, it's preferable to dig a little concrete out and cross "under" the pipework.
Easy for me to say here. There may be a good reason for the way they've done it.... apart from making life easier for them.

Anyway, no matter. Yes, cut the insulation as necessary to channel the pipework into it.
Unlikely as it may seem, it's standard practice to lay concrete or screed over insulation. When set, screed acts as a giant slab bearing on the whole floor. Its integrity is such that the load is distributed over the whole area.

If you divided the load by the floor area you'd find that the load per square inch/ sq. metre etc will be minimal.