finished floor with respect to DPC

Wavehopper

Hi all,
I was just wondering if my finished floor screed needs to be at least level with dpc or if it's ok to leave top of floor tile level with dpc?

I have radon barrier & dpc on inside leaf (and dpc on internal walls) ~230mm above sub-floor. I was planning to put in 140mm floor insulation and 80mm screed (over under-floor heating pipes) but that still leaves me shy of dpc level. Do I need to increase insulation level by another 10mm to bring top of screed level or could I take it that tiles + adhesive will be sufficient?

Thanks.

sinnerboy

Don't leave the DPC vulnerable to future alteration works . Bump up the insulation .

Poor Uncle Tom

If the insulation is brought up to 150mm and the screed is brought up to 100mm then you will have the margin of cover and protection needed.

sydthebeat

any exposed dpc will be damaged when floating, definitely bring screed over.

2 x 80mm PIR sheets, joints staggered
500 gauge slipping sheet
90mm screed floated

= 20mm over dpc level

Wavehopper

Thanks a lot for your replies to this.

I had intended finishing the screed just above radon/dpc but my window supplier installed the front/back doors about 20mm lower than I wanted which means that top of aluminium strip on door is level with radon rather than bottom of strip level to allow for floor tiles.

Insulation & screed won't be going in for another 6 wks or so.

Before I go back to them I wanted to know if top of tile (15mm tile + 5mm adhesive) would be acceptable to leave level with radon & dpc or if I should insist they take out the door and allow for floor screed to be level with radon which would then allow 20mm finished tile height.

Thanks.

Poor Uncle Tom

Wavehopper wrote: »

Before I go back to them I wanted to know if top of tile (15mm tile + 5mm adhesive) would be acceptable to leave level with radon & dpc

It would be acceptable to leave the top of the tile level with the radon and DPC.

Wavehopper wrote: »

or if I should insist they take out the door and allow for floor screed to be level with radon which would then allow 20mm finished tile height.

You can do either.

There are two things to watch out for here:

1. Not to damage the radon barrier or DPC when putting in the screed and tiles.

2. When all is finished that the radon barrier or DPC are not exposed or visible.

Either of the options you mention above expose the radon barrier to the same potential problem. The top of the screed will be worked with floats which can easily damage the barrier, the DPC should be ok. This is the main reason for finishing the screed above the barrier/DPC level.

If there is skirtings being used, the fixings should never penetrate the barrier and it should also be watched that the skirting does not 'pinch' the barrier if it is in contact with it where it lapps at the DPC level.

mickdw

I would keep the floor as close as possible to the underside of your DPC but I wouldnt go over it. IMO it serves a useful role in stopping any future leaks in floor etc damaging wall finishes as no water creap is possible up the wall as long as DPC is above the floor

Wavehopper

Thanks for your comments on this.

In the hall where the front & back doors are installed a bit low, I'll put in the 140mm insulation + 70mm screed + 20mm tiled floor to bring me level to radon/dpc. I'll talk to my plumber to see if 130mm insulation + 80mm screed would suit underfloor heating better.

For all other downstairs rooms, I'll either increase the insulation by 10mm or increase the floor screed by 10mm to bring me to 220mm + 10mm finished floor.

Mellor

mickdw wrote: »

I would keep the floor as close as possible to the underside of your DPC but I wouldnt go over it. IMO it serves a useful role in stopping any future leaks in floor etc damaging wall finishes as no water creap is possible up the wall as long as DPC is above the floor

Not if it tears when floating the slab.


If the floor was above DPC, no water can creep up the wall either as the barrier is still continous. (except of course for water coming from inside the house, but thats a bigger issue already)