Styrofoam and plaster on the outside of a lecawall

[tlundberg]

Hello

I have a basement wall made of leca that is insulated/drained below ground with 20cm of Isodrän. Above ground, I want to attach foam plastic of the same thickness. I would then like to plaster the wall.

How do I attach the foam plastic? I'm considering two layers of 100mm foam plastic. So, the first layer needs to be attached to the leca wall, and the second layer will be foam plastic against foam plastic. The entire structure needs to be stable enough to support a layer of plaster on top.

I have read a bit about using foam adhesive to glue the foam plastic. Will that hold? I also found a table on Essve's website where they recommended Stenlim Skum. Do you think that's better or worse than foam adhesive? They themselves write, "Do not use in load-bearing constructions." Is what I want to do considered "load-bearing"? It will bear a load in the form of plaster. If not gluing, then it’s likely screwing. Essve recommends their NL plugs for leca. Then it's just about finding a good screw and a sturdy washer to get as much contact surface as possible against the foam plastic. I need screws that are about 30 cm long. Where can I find that? And where can I also find a suitable washer to use?

 

[tlundberg]

Found a possible glue at: Stone glue - Biltema.se
It was @Peter2400 who suggested it here: https://www.byggahus.se/forum/threads/limma-med-polyuretanskum-fogskum.336503/#post-3219092

 

[tlundberg]

If I'm going to screw, I've found a few alternatives for screws here:

SWG 191 108 280 19 Wood Screw 8 mm 280 mm Multi-sided toothed Steel galvanized 50 pcs | Conrad.se 650 kr
JD Plus construction screw with Torx fitting 8.0x280 mm, electrogalvanized, yellow, 50 pieces - buy on HORNBACH.se 1077 kr
Wood Screw FAST Big DOG C4 Dimension: 8x280 mm, Content: 25 pcs- 281528 (bygghemma.se) 566 kr (note: only 25 pcs)

Am I looking at the right type of screw? Does the cheapest option from Conrad work?

When it comes to a suitable washer, is a plastic one sufficient, or does it need to be metal to provide enough pressure against the foam plastic?
Byggmax has a plastic one that is 60mm in diameter Spikbricka (P-21214) | Byggmax
Verktygsproffsen has one in 0.8mm aluminum that is 40mm in diameter. I don't know if it can provide stronger pressure, what do you think? VSB 98400 Insulation washer external, 100-pack Ø40 mm | Verktygsproffsen

 

[Screew]

Otherwise, plastic nails are quite convenient, but I don't know how well it would hold with plaster on the insulation. It might be worth looking into.

 

[vectrex]

I think you're exaggerating quite a bit when you want 200mm cell plastic outside the basement wall. Settle for 100mm. How much does the rest of the facade protrude beyond the basement wall?

Plastering directly on cell plastic also becomes very sensitive to damage. Use XPS or at least S200 EPS.

 

[tlundberg]

Otherwise, plastic nails are quite convenient, but I don't know how well they would hold with render on the insulation. It might be worth checking out.

Exactly. Like this one with pin from Byggmax ISOLERHÅLLARE MED STIFT (P-61020009) | Byggmax

The problem is that the weight will be vertical on the nail which is positioned horizontally. It's not really designed for that. Do you have any idea where or how to check if it would hold?

 

[Screew]

Exactly. Like this one with pins from byggmax ISOLERHÅLLARE MED STIFT (P-61020009) | Byggmax

The problem is that the weight will be vertical on the nail that is set horizontally. It's not really made for that. Do you have any idea where or how to check if it would hold?

The simplest way is probably to ask the supplier. They should be able to tell you if they work for what you have in mind. I recall that BEWI pustskiva can be mounted similarly.

 

[tlundberg]

I think you're exaggerating quite a bit when you want to have 200mm of insulation on the outside of the basement wall. Settle for 100mm. How much does the rest of the facade protrude outside the basement wall?

About 23 cm

Plastering directly on insulation is also very sensitive to damage. Use XPS or at least S200 EPS.

I could definitely do that.

 

[Gabbe1]

If you clamp the foam plastic against the base with battens and long screws. Then you can screw a baseboard into the battens.