Plaster on polystyrene?

[Oddbod]

When I started planning to fix the basement walls above ground, it was obvious that I would insulate with EPS and then apply plaster on it, but the more I google the subject, the more uncertain I become about how it should be executed.

There are a lot of threads here discussing the same subject, but a couple of things have caught my attention.

1. When installing EPS/Cellplast, can I use regular cellplast boards (S80) that I can buy at, for example, Bauhaus, or does it have to be a special board?

2. The wall currently consists of hollow concrete blocks, and I was planning to install double 30mm boards overlapping each other. How do I attach the boards?

/G

 

[b8q]

I did a similar thing a couple of summers ago. I bought tracked foam board, http://www.bygghemma.se/utomhus/bygg/isolering/cellplast/putsskiva-bewi-for-fasad/p-612093

which I then attached to my concrete block wall, for safety both with adhesive and with insulation fasteners; http://katalog.essve.se/article/?katBid=V70&dokId=wc398161&artNr=

(there are many different types, I liked the ones with metal nails the best).

Thereafter, mesh netting was attached, and the whole thing was plastered with Finja's plaster mortar. On one wall, I tested with fiber-reinforced plaster mortar to see if there was any difference over time. So far (2 years) none of the bases have cracked.

 

[Oddbod]

Do you think the tracked foam was necessary or would smooth EPS have worked just as well since you have reinforcement mesh anyway?

It looks like you used metal reinforcement mesh, is that correct?

Adhesive and then securing with what you linked to sounds like a smooth way to get the panels up.

 

[b8q]

1) I don't know, but it feels like the reinforcement is primarily there to hold the plaster together and prevent cracking, but it doesn't affect the plaster's grip on the underlying foam. The grooves make the plaster grip better on the foam, at least that's what I imagine.

2) Yep, standard galvanized plaster netting. I have no idea what is best, galvanized, stainless steel, or plastic. It was purely a question of price and availability for me.

 

[Oddbod]

Thanks for the quick answers! I will use smooth EPS with galvanized reinforcement, and we'll see if it holds.

 

[Fjojtmehmet]

The idea with the tracked ones is probably to create paths for the air to travel between the board and the existing wall.

 

[nimhed]

Yes, I also mean that the tracks should be against the wall and not against the plaster.

 

[b8q]

Yes, I also mean that the tracks should be against the wall and not against the plaster.

No, that sheet has knobs on the wall side too, for an air gap.

 

[nimhed]

Ahh, ok

 

[Maxwells demon]

Saw someone in the area who had an older gentleman from a company that insulates and plasters the base. Carpenter or mason wasn't clear. Right or wrong, I don't know either. But I saw that he used regular smooth foam board which he scored the plaster side with a handsaw. Assuming for adhesion. Looks good from the street after 3 years at least. Mechanical attachment was used I saw. So some kind of insulation holder.

 

[Oddbod]

Ok... should one wait to tear down the plaster side until the first snow has settled so that the neighbor thinks it's snow blowing over onto their property? =)

 

[b8q]

Not at all, that board also has knobs on the wall side, for an air gap.

This is what it looks like, outside and inside respectively:

 

[mr.Ola]

Thanks for the quick responses! Will run smooth EPS with galvanized reinforcement and we'll see if it holds.

How did it go with the plaster on the cellular plastic? Are you satisfied with the result? I'm considering something similar, which is why I'm asking!

 

[Oddbod]

How did it go with the plaster on the foam plastic? Are you satisfied with the results? I'm considering something similar, which is why I'm asking!

Still holding up and looks nice. I chose fiber-reinforced plaster in addition to mesh and installed a drip edge above the boards and under the panel to ensure that moisture doesn't get in.

 

[LevaLivet]

Still sitting nicely and looks good. I chose fiber-reinforced plaster in addition to mesh and then placed a drip edge above the boards and below the panel to ensure that no moisture gets in.

Do you possibly have a picture showing how you finished up towards the panel?