We have bought a house from Sävsjö Trähus and we're going to have a rendered facade. On the outside of the house, there is exterior gypsum and on this, a so-called render carrier is to be attached. We are choosing between two options:
1. EPS (styrofoam)
2. Mineral wool/Rockwool
Depending on who you talk to, either EPS or mineral wool is recommended. The problem is that it is claimed that mold can form in the exterior gypsum depending on the choice of render carrier and how the exterior gypsum has been handled. This can (depending on who you talk to) occur with both the EPS and the mineral wool. STO and Finja recommend EPS and Maxit recommends mineral wool.
What to do??? Is there anyone who knows an impartial expert that can be consulted in this matter? It wouldn't be very nice if mold appeared in the house in a few years...
1. EPS (styrofoam)
2. Mineral wool/Rockwool
Depending on who you talk to, either EPS or mineral wool is recommended. The problem is that it is claimed that mold can form in the exterior gypsum depending on the choice of render carrier and how the exterior gypsum has been handled. This can (depending on who you talk to) occur with both the EPS and the mineral wool. STO and Finja recommend EPS and Maxit recommends mineral wool.
What to do??? Is there anyone who knows an impartial expert that can be consulted in this matter? It wouldn't be very nice if mold appeared in the house in a few years...
I have no clue about rendered facades, but cell foam (EPS) is significantly denser than mineral wool when it comes to water and absorbs relatively little water. I think that at least should speak for the cell foam.
A website with a bit about EPS
http://www.sundolitt.se/default.asp?menu=409&id=
...Then there's another variant of cell foam - XPS (extruded instead of expanded) which is significantly denser than the regular EPS (and of course more expensive...)
A website with a bit about EPS
http://www.sundolitt.se/default.asp?menu=409&id=
...Then there's another variant of cell foam - XPS (extruded instead of expanded) which is significantly denser than the regular EPS (and of course more expensive...)
What might argue against plastic on the outside is that it seals the frame. Then you have a waterproof layer on the inside (diffspärren) and one on the outside (the EPS)....
Well, many, many houses are plastered with both methods. The EPS variant is usually cheaper because they use thinner plaster. It is less labor- and time-intensive.
Well, many, many houses are plastered with both methods. The EPS variant is usually cheaper because they use thinner plaster. It is less labor- and time-intensive.
Stupid question: As I said, I don't know how a plastered wall is constructed, but there's no air gap anywhere - that is, inside the outside gypsum board/chipboard to which the plaster carrier is attached?Fasting65 said:
..just a little curious..
We have built a house with a rendered facade where we used EPS boards as a render carrier on outdoor gypsum boards. Works perfectly.
What you should consider when applying the EPS to the outdoor gypsum is that it's not good if it has rained on the gypsum so that the exterior "paper" is wet. Then you are essentially trapping the moisture between the gypsum board and the EPS.
The render itself, which is applied to the EPS, does not mold. It is supposed to withstand both weather and wind.
Also, keep in mind not to render in direct sunlight as the mortar sets too quickly and so on. But perhaps you already knew that.
What you should consider when applying the EPS to the outdoor gypsum is that it's not good if it has rained on the gypsum so that the exterior "paper" is wet. Then you are essentially trapping the moisture between the gypsum board and the EPS.
The render itself, which is applied to the EPS, does not mold. It is supposed to withstand both weather and wind.
Also, keep in mind not to render in direct sunlight as the mortar sets too quickly and so on. But perhaps you already knew that.
I believe both methods work - if you follow the instructions provided by the suppliers. It's often there that it falls short...
For our house without a vapor barrier, they didn't recommend that I install Styrofoam sheets because moisture can become trapped in the construction.
For a modern house, I think it matters less which system you use...
For our house without a vapor barrier, they didn't recommend that I install Styrofoam sheets because moisture can become trapped in the construction.
For a modern house, I think it matters less which system you use...
Fun that so many have responded to my question 
My interpretation is that foam plastic seems to be a better solution...
In any case, the plastering will be carried out by a contractor. Currently, it leans towards a plaster system from STO with foam plastic as a plaster carrier. This is recommended by the contractor, but they also say that it works well with mineral wool as a plaster carrier.
The downside is that some people at home(!) strongly advocate for the solution with mineral wool! To be continued...
My interpretation is that foam plastic seems to be a better solution...In any case, the plastering will be carried out by a contractor. Currently, it leans towards a plaster system from STO with foam plastic as a plaster carrier. This is recommended by the contractor, but they also say that it works well with mineral wool as a plaster carrier.
The downside is that some people at home(!) strongly advocate for the solution with mineral wool! To be continued...
I interpret it completely the opposite, but it's more the plaster thickness and coloration that I'm focusing on.
Thick plaster on mineral wool is 2 cm thick and reinforced with galvanized steel mesh, while the plaster on styrofoam is only about five to seven millimeters thick on fiberglass mesh.
Thick plaster also has colored-through surface plaster - no paint that is rolled on. The thick plaster looks more vibrant as it often contains dolomite (mica).
Mineral wool allows moisture to pass through, i.e., it does not seal the house (which can be harmful if the house is old and lacks a vapor barrier).
Yes, that's my very personal and subjective opinion. After all, I have chosen Optiroc's/Maxit's Serposystem with mineral wool slab and thick plaster. People tend to defend their own choices with strong arguments.
Thick plaster on mineral wool is 2 cm thick and reinforced with galvanized steel mesh, while the plaster on styrofoam is only about five to seven millimeters thick on fiberglass mesh.
Thick plaster also has colored-through surface plaster - no paint that is rolled on. The thick plaster looks more vibrant as it often contains dolomite (mica).
Mineral wool allows moisture to pass through, i.e., it does not seal the house (which can be harmful if the house is old and lacks a vapor barrier).
Yes, that's my very personal and subjective opinion. After all, I have chosen Optiroc's/Maxit's Serposystem with mineral wool slab and thick plaster. People tend to defend their own choices with strong arguments.
Hi, as I see it, foam plastic is far better than mineral wool. I'm a mason myself and do a lot of plastering, so I know what can happen with mineral wool in case of rain. It usually takes at least a couple of days before the mortar is applied to the insulation, and during that time it can absorb massive amounts of water, which can potentially lead to mold and likely cracks in the plaster.
I can also recommend STO as a plaster system. The result is superb, all materials are reinforced, and STO provides everything needed for weatherproofing attachment points, etc. They take full responsibility if something happens to the plaster, provided the plastering company does as STO instructs. It's self-evident that this thin plaster becomes more durable. Thick plaster becomes its own lever.
I can also recommend STO as a plaster system. The result is superb, all materials are reinforced, and STO provides everything needed for weatherproofing attachment points, etc. They take full responsibility if something happens to the plaster, provided the plastering company does as STO instructs. It's self-evident that this thin plaster becomes more durable. Thick plaster becomes its own lever.
But wait here... Regardless of the building method, you make sure to protect the house properly.
Any water from the roof should be diverted to avoid any moisture problems in the construction. This applies throughout the entire construction period.
Moreover, it's the walls being plastered—not the roof. The amount of water that would hypothetically hit the wall is negligible. The plaster itself likely contains more water than any potential rainwater that would hit the facade.
I'm afraid I don't understand what you mean by thick plaster being its own lever. Would the plaster fall off under its own weight? I'm no expert in plastering, but you'll need to elaborate on your reasoning. In our residential area (and many others), thick plastering has been done since at least the 1930s. In some cases, these thick plasters have had to be redone, while in others, they still hold up...
EDIT: Of course, even thick plaster is reinforced. The plaster contains a certain amount of fibers (fiberglass?) as well as the galvanized, spot-welded steel mesh.
Any water from the roof should be diverted to avoid any moisture problems in the construction. This applies throughout the entire construction period.
Moreover, it's the walls being plastered—not the roof. The amount of water that would hypothetically hit the wall is negligible. The plaster itself likely contains more water than any potential rainwater that would hit the facade.
I'm afraid I don't understand what you mean by thick plaster being its own lever. Would the plaster fall off under its own weight? I'm no expert in plastering, but you'll need to elaborate on your reasoning. In our residential area (and many others), thick plastering has been done since at least the 1930s. In some cases, these thick plasters have had to be redone, while in others, they still hold up...
EDIT: Of course, even thick plaster is reinforced. The plaster contains a certain amount of fibers (fiberglass?) as well as the galvanized, spot-welded steel mesh.
It's a bit surprising to hear a mason talk about how much better cellular plastic is, that mineral wool can mold, etc. I think he's speaking out of ignorance. I have plastered several houses with thick plaster on mineral wool and have spoken with suppliers about how long the insulation can remain uncovered before it needs to be plastered. Both manufacturers that produce plasterboards say that you can easily leave the facade open for 4-6 months before you need to apply the plaster layer. And that it would then mold in the insulation—how is that? We're talking about an inorganic material! And all suppliers provide guarantees, it's nothing unique to STO. Sto on cellular plastic is certainly a good option when you want thin plaster, but don't criticize thick plaster with unfounded claims!! Best regards / Anders