Plaster mortar ?

[Draven]

Going to plaster the garage's interior walls made of lightweight concrete (ytong), which plaster should I buy?

 

[ktm250]

Low-alkaline.

If you are using maxit's products, start with Serpo 105, vitgrund, and then plaster with Serpo 131, Ytongputs C. Alternatively, you can plaster with Serpo 138, tunnputsbruk. It depends a bit on irregularities and so on. The most important thing is that you use low-alkaline products to prevent ettringite formation.

edit: apologies for the spelling mistake

 

[jon_h]

You should use a low-alkaline render mortar, B or C depending on the strength requirements.

Edit: ktm250 got there first. (ettringite is what it's called)

 

[Draven]

Okay, thanks..

 

[Draven]

Is Byggmax Plaster C low-alkaline you think?
I still have some sto plaster that I've used on the interior walls of the house which is low-alkaline, considering using Byggmax Plaster C and then this as the outer layer on the interior walls in the garage, does it work?

 

[jon_h]

Byggmax Putsbruk C is it low-alkaline do you think?
I still have sto plaster that I used for the interior walls of the house, it's low-alkaline, considering using byggmax plaster mortar c and then this on top for the interior walls in the garage, will it work?

A low-alkaline mortar is special, so it says on the bag if it is. I absolutely don't think their regular Putsbruk C is it.

How do you mean, first regular Putsbruk C and low-alkaline on top of that? No no, the low-alkaline must be against ytongen, but I think as long as it's low-alkaline directly against the ytongen, you can put regular mortar on top. But I'm not a hundred percent sure about this. Check with the manufacturer if no one else here knows for sure.

 

[ktm250]

Go with low-alkaline all the way.
Hypothetically, you could use alkaline on the outside, but the slightest moisture migration can result in it being a bad move to use alkaline. Any guarantees are void if you use alkaline on low-alkaline.
Byggmax Putsbruk C is not low-alkaline.

 

[anra]

Is it necessary to use Serpo 105, white primer, before applying Sepro 138, thin plaster? My walls (also in the garage) were plastered a long time ago, but now the plaster has started to come off in various places, so I'm considering applying a new layer of plaster.

 

[Crille Danielsson]

Do you have to prime with Serpo 105, white primer, before applying Sepro138, thin render mortar? My walls (also in the garage) were plastered a long time ago, but now the plaster has started to come off in various places, so I am considering applying a new layer of plaster.

I haven't used Serpo 138, but if it's similar to other thin render systems, you usually prime the aerated concrete, then apply the adhesive mortar in 2 layers; in the first, you embed the fiberglass mesh. The second layer is sponge finished or broom finished before surface render or paint.

 

[ktm250]

I haven't used Serpo 138 but if it's similar to other thin plaster systems, you usually prime the aerated concrete then apply the adhesive mortar in 2 layers; in the first layer, you embed the fiberglass mesh. The second layer is floated or broomed before applying the top plaster or paint.

It's not the same/similar. Very old thread...