Walls and Ceilings - Plaster on Cinder Block Walls?

I recently purchased the duplex that I live in, and I'm looking for a suitable product available in the US that I can use for putting a textured plaster coating on cinder block walls--hopefully one with insualting qualities. My priorities are aesthetics, low cost, simplicity, and insulation (if possible) My house is built of cinder blocks, and already has a stucco finish on the outside, but that was done with just plain old stucco (cement-based) and has no insulating qualities. It's no surprise that in the summer, the blocks heat up all day long, then slowly release that heat back into the house during the evening. Long after temps drop down to under 70 degrees outside, my walls are still 77-80 degrees after a warm sunny day. (Just like how pavement is hot well into the evening). In the winter, it seems as though the cold air is passing in and it is always kinda chilly no matter how much I crank the heat. If you feel the exterior walls, they are cool to the touch even though the house is heated to 70. The more I have read, I think that actually what's happening is my inside heat is transferring through the cement to the outside. I have new thermal windows throughout, but that can't do anything about this. (obviously, I'm not an engineer)

I always figured the easiest way to partially remedy this was by re-plastering the inside of my exterior walls with something that doesn't conduct heat as well. I have learned of a few different products that use additives to regular plaster to reduce conductivity. I have found a few companies in Europe, Canada, and New Zealand that sell such a product, but none in the US. Some of the products use gypsum (perlite), but the one that showed the most promise was a British company that has a cement based plaster mixed with expanded polystyrene beads.

http://www.walltransform.co.uk/

I e-mailed this company to see if they knew who I could talk to in the US, but no answer. This would be ideal because I could apply it for now on the interior and maybe eventually do the outside as well. The outside is textured and would require a lot more prep and surface area to cover. It would have been nice if they had wrapped the building with that 3M film or something before they put the stucco on.

I thought about drywalling and insulating the inside, but that would be a pain working around all the windows, doors, and trim, all the dust and sanding, and would take away a few inches off of already small rooms. Also, since it's a rental, concrete walls are a lot harder to damage. It's simple enough to hang things with a masonry bit.

I also found a paint additive called Insuladd which contains hollow ceramic spheres that I could paint over regular plaster. This shows promise, and is available in the US, but I don't know if it would be as good at insulating. It basically doubles the cost of painting the house, as they sell packets to add to any regular paint for $12.95 per gallon kit. It would definitely be the easiest option.

http://www.insuladd.com/index.htm

I found a wall texturing plaster at Lowe's called Homax for only $9 for enough to cover 450 sq. ft, and says it can be trowelled, rolled, or sprayed. I'm not sure if I could cover all the joints to hide the block with this, or if I'd need to apply something else first. It doesn't say it has insulating properties, but it does contain perlite, so it may help.

(Sorry so long. There were other similar threads, but I didn't want to hijack. I considered the insulation or energy sections, but I thought this fit better.)

Welcome to the forum

I have lived in a house similiar to yours in fla. Built for 2k in the 50's. I'm suprised to hear of one being built that way so far north. SWP sells an attic coating that is supposed to reflect heat but I don't know if that would help in your situation or not. I believe the most effective thing to do is to fur out the walls, insulate and drywall. But then you said you didn't want to go that route. I doubt that there is a 'magic' fix to give more R value to the block.

I'll give it a try. This advice is worth what it costs you.

I suppose the walls have been painted so you would need to use a bonding agent which is the second best option or lath it with either metal lath or chicken wire if you can nail it or screw it to the blocks. There is a change that water vapor could get into the wall and maybe condense at the surface of the bonding agent. I don't know but it might.

Now for the plaster material. I think you could find some polystyrene beads to use for aggregate. I think you would need a few different sizes of beads to get a good mix much like there are various sizes of grains of sand in good plaster sand. Mix according to volume and If you use gypsum plaster start with equal volumes of plaster and sand. See how hard and strong the mix is and you might be able to use more beads.

The same could be done with Portland cement. I think you could start with maybe two parts foam to one part cement by volume and you might need some hydrated lime for workability.

I have no idea what kind of thickness you will need to get significant insulation but I suspect a lot.

Now yet another way is to use polystyrene foam and then plaster or drywall over that. even 3/4" of foam will be some good insulation. it can be adhered or fastened mechanically.
there is a potential risk of the foam releasing deadly gasses in case of a fire so every edge and surface would need to be encapsulated against fire. There are probably some engineers who know about this and I think that as a rule it is discouraged for interior use. Check it out before doing it but it is worthwhile insulation.
Let us know what you learn on this one and what you do.

Thanks for your input! I had wondered about surface prep. The Homax product said for painted surfaces you should sand it rough. Most of the walls are painted with semi-gloss, so I was thinking of rolling a primer coat on. What type of bonding agent did you mean?

I also wondered about trying to find polystyrene beads or 'ceramic spheres' like that paint additive has, but I figured they would be hard to find--especially for individual (small-scale) use. Any ideas on where to look? Quite frankly, I'm about to give up on finding a product to increase the R value and just go with some kind of regular plaster like that Homax. I may start by using that on interior walls next door since I'm about to ready it for renting and I can't stand looking at these painted block walls. If I don't find something else soon, I'll just go with this and then try the paint additive inside and out, although that will get expensive if I don't make up my own 'mix'.

This guy in the UK seems to have a good product--his company is a new start-up and it is taking off. He was a plasterer before he started the company. A US entrepreneur ought to get with him and bring it here. We don't have many block or stone homes, but think of all the commercial buildings here that could use this.

The best bonding agent is Plaster-Weld or Weld-Crete both by Larsen's Products. google them.
The beads I have in mind are the same as they use in bean bag furniture. If you have a foam fabricator they should be able to help you out. You could also use reground foam. In fact it might be better because the sizes would be more varied and they would be sharper. Irregularly shaped aggregate is better than spherical.

I don't know why I didn't think of this last night but your best solution but certainly not the cheapest nor most amateur friendly is to use an Exterior Insualtion and Finish System.(EIFS) There are many brands of this but probabaly the most well known is DRYVIT. Now you might have heard some bad things about EIFS but over masonry it is a very good system and will give you the insulation where it will do the most good and will give you a new exterior. Now if it is the aesthetics of the block on the inside you can do something easy to make them look plastered.

Look under stucco and exterior coatings and ask around there are probably some EIFS contractors around who can give you bids and you might be surprised at the cost vs. payback on the system.

Of course you also need to make sure there is adequate attic insulation too.

Keep us posted on what you learn and what you do.

I called the only 3 or 4 'Foam Products' companies in the book, and none had what I'm looking for. If I do find it and mix it with the plaster, do you think it will rise to the surface and be visibly exposed after it dries? I think I'm going to go ahead with that Homax for the internal walls at least. I saw calcium phosphate and perlite in the ingredients on the label--does that mean it is gypsum based as opposed to Portland cement? Which type would be better? I see Lowe's doesn't sell the Larsen's bonding agents. I suppose I'll see what they do have, or otherwise there is a builder's supply on the other side of town that has Larsen's. Can this stuff just be rolled on?

Regarding polystyrene in plaster ot concrete -

Polystyrene is normally not compatible with concrete.

The water in the mix does not wet the surface and allow the concrete to bond to it. People have been able to overcome this with a couple of different additives, but no product has been developed and marketed - No real need, I guess.

It is difficult to mix the beads with the concrete materials because of the huge difference in the density of the materials (150#/cf versus 1#/cf). The mix segregates very easily. Russians use some, but also use lightweight aggregate (40#/cf) with the sand. The softness of the polystyrene beads cause them to deform and break away from the cement easily.

In Europe, where most housing is concrete or masonry instad of wood, lightweight plaster is used on interior walls. I beleive the aggregate is perlite or a volcanic material such as tuffa or pumice. It is not durable enough for outside. It takes very sophisticated materials and equipment plus having the skill. I don't think you will have a great deal of luck in the U.S.

Dryvit would be more effective on the exterior of a heavy wall since it gives the benefit of thermal inertia that minimized temperature and humidity swings. Dryvit is a good system on masonry or concrete, but a big problem on wood structures.

Dick

Dick

That's what I was starting to wonder about trying to mix it myself. Did you look at this Wall Transform company from the UK? This guy seems to have figured it out and it says it's for interior and exterior use. I saw a show on the Science Channel about plaster with some additive, but I can't remember what it was, but they described it as reflecting the thermal energy therefore not allowing it to pass through. Some companies from Germany have a product that mixes in parrafin, but I think that's geared more towards keeping a building cool. Other's have used perlite, and of course there's the paint with ceramic beads. The ceramic thing could possibly work for plaster but where do you get ceramic beads without paying $12.95 for a small packet? When I first started thinking about this, I envisioned something that looks like plaster but was actually synthetic and less conductive (rubber, vinyl??) I might eventually look into an EIFS system for the exterior, but right now the exterior is stucco and looks good and there are many other areas that need attention ($$). I would like to make it more comfortable and energy efficient, but I have to try to spend my money where it best affects rental value and adds to the market value of the property.