Uneven insulation and UFH piping

gunnerfitzy

Hi all,

Again, I renovating a cottage in East Cork. I had the existing floor dug up, a new sub floor put down, radon barrier, xtratherm insulation and UFH piping. The screed is due to be poured next Wednesday.

I have noticed in the kitchen that there are areas when the heights of the xtratherm insulation are uneven. In areas this is unevenness is in excess of 1 inch.

Because of this and the plastic membrane between the insulation and UFH piping/concrete screed I am concerned that a pocket will develop under the screed (which would be of uneven depth) and that this would crack probably damaging the UFH piping.

The builder has stated that this unevenness is due to the foundation he discovered when the old floor was taken up. I have spoken to the UFH heating engineer who says that this 'void' under the membrane needs to be filled preferably by insulation cut to size or alternatively sand but my concern remains.

A picture is attached. I would great appreciate any advice anyone has to offer.

Thanks in advance.

It would be better to build up the insulation to keep the thickness of the concrete the same, otherwise you could end up with a "cool spot" as this section of pipes may end up deeper in and it would also need to heat up a greater mass of concrete.

heinbloed

The ground/rubble/clean layer must be level. Anything else when pouring liquid concrete over boards will lead to un-even settlement. The edges of the boards will sink uneven, a step would between them created. Which in turn is a thermal gap.
Your builder has to do the job again. This means compacting the rubble, put a leveled clean layer on top (the sand your UFH company recommends goes UNDER the insulating boards) and then the insulation again.

Poor Uncle Tom

It is not a good building practice to leave a void between the insulation and the screed. When the screed sets and the traffic starts on the floors over any void spaces there will be pressure put on the screed, the membrane and the pipework for which non of them are designed. You could end up with a torn membrane, cracked screed or damaged and punctured pipes.

kboc

Do not let them pour the slab.
2 possible ways to fix it

1. easiest is to put sand UNDERNEATH insulation as mention before. I done this in mine house where prestressed slab met RSJ. Filled void with sand.

2. spry exapnsion foam, let dry. Get carpeners saw and cut so fill vois. You will still have a "slope" on your insulation boards, not a big deal and certainly better than the way it is.

Plumber was a bit slack in working over that. Did he not highlight this to you?

Remember; golen rule, this is your house not some builder who is (probably) driven by money and not his reputation and definetly not your quest to heat the house for as little as possible.

Never accept second best. Politely ask him to fix it.

Good luck

gunnerfitzy

Thank you all for your comments and suggestions.

I was indeed surprised that the UFH installers decided to put the piping down over this.

I have spoken to my engineer about this today and he has recommended that the membrane be cut at the joint and that the joint be sealed with tape. This would mean that there would be deeper concrete at this particular area. He mentioned that the additional concrete is preferable to having sand under the membrane and above the insulation. However dolanlbaker has mentioned that this could cause a cold spot as there is more concrete to heat in that area.

I had mentioned the expanding foam solution to the builder but he said at €10 a tube it would be a bit costly. I would not mind the cost if this was a good solution.

Any further suggestions would be most welcome.

sheff the ref

How did you resolve this and has there been any long term consequences?