When to fit edge Strip

[GrantMcscott]

Hi,

I am currently fitting my insulation for my underfloor heating and have done the following

 

• Laid 1200 gauge DPM on concrete slab
• Installed 25mm PIR insulation as and upstand from the concert slab to top of screed
• Laid 2 layers of insulation with joints staggered

 

My question is what do I do next 

 

1

• Install expansion edge strip for the screed
• Lay 500 gauge DPM do not take it up the walls 
• Tape DPM to apron of edge strip

 

2

 

• Lay 500 gauge DPM take up walls and tape to Wall Vapour control layer
• Install expansion edge strip for the screed
• Tape DPM to apron of edge strip

Edited January 12, 2022 by GrantMcscott
added pics

[JohnMo]

The PIR upstand will be your expansion strip, you don't need a further expansion strip.

 

You put polythene / DPM over the PIR only to stop a chemical reaction between the aluminium foil and the cement in the screed.  I cut it flush with top of screed after the pour.

 

The order my floor was build.  Finished floor went in prior to the walls, on our build.

 

DPM

Structural steel re-enforced concrete slab.

200mm, in two layers of PIR, with 70mm upstand

Thin black polythene.

Staple UFH piping to PIR through poly sheet.

Instead of screed, I have C34 fibre re-enforced concrete above the insulation/UFH pipes, 100mm thick.

 

 

 

 

[GrantMcscott]

8 minutes ago, JohnMo said:

The PIR upstand will be your expansion strip, you don't need a further expansion strip.

 

You put polythene / DPM over the PIR only to stop a chemical reaction between the aluminium foil and the cement in the screed.  I cut it flush with top of screed after the pour.

 

The order my floor was build.  Finished floor went in prior to the walls, on our build.

 

DPM

Structural steel re-enforced concrete slab.

200mm, in two layers of PIR, with 70mm upstand

Thin black polythene.

Staple UFH piping to PIR through poly sheet.

Instead of screed, I have C34 fibre re-enforced concrete above the insulation/UFH pipes, 100mm thick.

 

 

 

 

Is there enough movement in the PIR insulation as it has a good compression strength.  I have one room that is 12.5 x 5.5 m I would of thought it needs more movement that the PIR will give  

[JohnMo]

We don't seem to have any issues.

 

My thought process was.  You pour the concrete, it fills the space fully, as it drys the concrete shrinks, you heat the house, the concrete expands to fill the gap.  Plus that what the architect and structural engineer had on the drawing.  Our longest run of floor is about 13m.