Help - dpc insulation….

[Devil_bri]

I’ve googled the life out of this and can’t find the info I need, I’m sure it’s out there but I can’t find it….

I have the foundation in for a 7mx5m block garden room, with 100mm cavity. It falls under permitted development so no need for PP or BC. 
I am about to get the footings put it then I will fill the floor with the usual hardcore, sand, DPM, 100mm insulation, anther sheet of the DPM and then 100mm concrete. Which layer of DPM do I need to tie in with the dpc on the walls, the bottom or top layer or both ?

thanks 

[markc]

6 minutes ago, Devil_bri said:

I’ve googled the life out of this and can’t find the info I need, I’m sure it’s out there but I can’t find it….

I have the foundation in for a 7mx5m block garden room, with 100mm cavity. It falls under permitted development so no need for PP or BC. 
I am about to get the footings put it then I will fill the floor with the usual hardcore, sand, DPM, 100mm insulation, anther sheet of the DPM and then 100mm concrete. Which layer of DPM do I need to tie in with the dpc on the walls, the bottom or top layer or both ?

thanks 

Top one, technically you don’t need a dpm under the insulation unless you are using wool or some other absorbent insulation

[Canski]

We usually do the bottom one but as mark says it doesn't really matter

[Temp]

29 minutes ago, Devil_bri said:

It falls under permitted development so no need for PP or BC. 

BC might still be required if internal area over 30sqm.

 

[Devil_bri]

13 minutes ago, Temp said:

BC might still be required if internal area over 30sqm.

 

No not interested as internal floor area is under 30sqm, made of incombustible material and not used to sleep in. 

[Iceverge]

I'd get rid of the bottom DPM, it's not achieving much apart from trapping water in your floor buildup. 

[Devil_bri]

2 hours ago, Iceverge said:

I'd get rid of the bottom DPM, it's not achieving much apart from trapping water in your floor buildup. 

That does make sense 

[Devil_bri]

4 hours ago, Iceverge said:

I'd get rid of the bottom DPM, it's not achieving much apart from trapping water in your floor buildup. 

But is there not a chance of damp degrading the insulation. I’m using kingsman tf70, 100mm ??

[Canski]

If you want to be safe lap the DPM from below the kingspan. What harm can it do ? Double safe tape the top one up against the wall, It will make it easier to finish your concrete. I'm not sure where the trapped water is supposed to come from unless its raining. 

[Iceverge]

11 hours ago, Canski said:

water is supposed to come from unless its raining. 

 

This unfortunately, insulation floating around in a swimming pool kept in by the DPM with a concrete lorry impatiently waiting to pour.