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Hi all,
I currently have a brick - cavity - block external wall construction in the ground floor going up into a single block wall for the first floor. I intent to apply external wall insulation in both floors eventually to eliminate thermal bridges and improve overall performance.
I have some questions around insulating below the DPC though. My current general thinking and after consulting with Kingspan as well, is described below and in the diagram attached:
- Liquid tanking membrane below the DPC but connecting to it
- Kingspan styrozone H350R below the DPC fixed to the wall all the way to the foundations
- Drainage membrane
- Geotextile membrane
Above DPC will be "standard" EWI, Kingspan K5 boards finished with appropriate mesh and render sitting on a PVC track to avoid cold bridging. I don't need a lot of thickness as I will have the cavity wall beads, so I was going to go for 30mm maximum on the boards.
My questions:
1. I've read about putting a french drain at the bottom foundation level, wrapped in gravel and geotextile membrane, to drive away ground water. I was also thinking of a french / aco drain at the ground level for similar reasons. Does it make sense to use both??
2. What should take place at the interface of the K5 boards and the below DPC styrozone boards? Should those be butted together? Should there be a gap for some reason?
3. What should happen with the drainage membrane and the geotextile membrane around the styrozone boards? Fold around its top and underneath the K5 boards? Connect and overlap with the DPC? Something else entirely?
4. There are some airbricks below the DPC, any ideas what to do with those?? The floor is block and beam rather than timber, but still. The airbricks have been blocked by soil for years by the previous owner, but I'd like to do things properly.
5. I was planning of insulating the 50mm cavity with platinum beads but should this go all the way to the foundations or stop at the DPC?
I appreciate there may be some challenging questions there (at least they seem so to me!) and I am hoping I will get some good responses in this forum!
Many thanks in advance
I currently have a brick - cavity - block external wall construction in the ground floor going up into a single block wall for the first floor. I intent to apply external wall insulation in both floors eventually to eliminate thermal bridges and improve overall performance.
I have some questions around insulating below the DPC though. My current general thinking and after consulting with Kingspan as well, is described below and in the diagram attached:
- Liquid tanking membrane below the DPC but connecting to it
- Kingspan styrozone H350R below the DPC fixed to the wall all the way to the foundations
- Drainage membrane
- Geotextile membrane
Above DPC will be "standard" EWI, Kingspan K5 boards finished with appropriate mesh and render sitting on a PVC track to avoid cold bridging. I don't need a lot of thickness as I will have the cavity wall beads, so I was going to go for 30mm maximum on the boards.
My questions:
1. I've read about putting a french drain at the bottom foundation level, wrapped in gravel and geotextile membrane, to drive away ground water. I was also thinking of a french / aco drain at the ground level for similar reasons. Does it make sense to use both??
2. What should take place at the interface of the K5 boards and the below DPC styrozone boards? Should those be butted together? Should there be a gap for some reason?
3. What should happen with the drainage membrane and the geotextile membrane around the styrozone boards? Fold around its top and underneath the K5 boards? Connect and overlap with the DPC? Something else entirely?
4. There are some airbricks below the DPC, any ideas what to do with those?? The floor is block and beam rather than timber, but still. The airbricks have been blocked by soil for years by the previous owner, but I'd like to do things properly.
5. I was planning of insulating the 50mm cavity with platinum beads but should this go all the way to the foundations or stop at the DPC?
I appreciate there may be some challenging questions there (at least they seem so to me!) and I am hoping I will get some good responses in this forum!
Many thanks in advance
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