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a bit of a different situation

My situation is a bit different, we have a block home, and would like to smooth out our interior block surfaces. Last summer we insulated all of our exterior walls with XPS, and then sided it.

Therefore, we would like the wall to breathe (whatever moisture may get into it) toward the interior. I have read that the quickwall (or surface bonding cement) product seals and waterproofs the wall, which is what we DONT want.

Half of our exterior walls are bare, unpainted block, but the other half have been painted (the paint has been scraped and wire brushed and is well secured)

What would be the best options for us?

Firstly, I am confused about when someone refers to "plastering" a wall whether they are using plaster of paris, cement based product, or simple drywall spackle.

So, We have access to a drywall texture sprayer/gun... For the half that is not painted, what if we filled all the joints with mortar (very thin layer) and then threw the texture on it and painted, would that work?
For the part that is painted we would add the step of painting "plaster weld" on the walls first, then mortaring the joints and then spraying the texture on.

Am I crazy for thinking this would work?

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Posted 2011-06-13T22:18:44+0000  by rollupsleeves rollupsleeves



Hi there rollupsleeves and welcome to the community.


I wouldn’t call it a "a bit of different situation" I would call it a "a bit of good situation “.


Because of its high compressive strength and moisture permeability XPS or extruded polystyrene it is probably a best insulator that you can have on the exterior of your concrete block wall (CBW).

Two inches of XPS has 0.55 permeability and walls insulated or constructed with XPS are not required to have an additional vapor retarder (barrier).



Vapor retarder it’s a barrier that is applied to the exterior walls in order to minimize moisture permeability from outdoor elements in nowadays new construction. Having XPS applied to the exterior of your home it’s like bringing your home up to the newest standards.


This said I wouldn’t be to concern about high levels of moisture getting in to the walls insulated with the XPS.

You can confirm this with a moisture meter or by simply taping a piece of clear plastic on to the unpainted section of the concrete wall.

CBW walls with normal levels of moisture can be finished with standard gypsum coatings (drywall and drywall compounds).

Walls with higher moisture levels should be finished with cement (portland) base materials due to moisture resistance (cement base spray texture)


Your method would work with walls that have a normal moisture levels.

Mortaring joins would really not be necessary ,you can also  fill these with gypsum ( drywall )compound being that you are planning on finishing walls with drywall texture which is essentially also a gypsum base material.

I would recommend Durabond compound for the joint fills.


Finally on the wall assembles that are designed to dry to the interior only vapor permeable paint (latex) should be used

Hope this helps and good luck with your project.




Posted 2011-06-14T18:21:16+0000  by George_HD_CHI
Thanks so much, We will give it a go....
Posted 2011-06-16T03:25:13+0000  by rollupsleeves
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