mudgirl

Does anyone have any experience with applying drywall mud to a cement surface? I am building a pumice block and cement house in Mexico and would like to achieve a smoother, more workable finish on the inside walls than the traditional cement plaster which is normally used here. I was wondering if drywall mud would stick, and even if it sticks initially, would it flake off with time and changes in humidity?
They do get smooth surfaces here by using what is called "polido" or white cement, which in fact is not cement at all, ( but no one seems to be able to tell me exactly what it is) and almost always develops hairline cracks.
Any suggestions welcome, but not all (what an understantement)materials are available here.

concretemasonry

I am not aware of too many block in Mexico being made from pumice.

If they are actually pumice, you will find that pumice has a great ability to absorb a lot of moisture quicky.

Because of this, you may want to prewet the block a little ahead of time. The high absortion can suck the water out too quickly, causing closely spaced shrinkage cracks in the surface. - Two coats instead of one might be easier.

In some countries where pumice block is a common building material, a first coat of plaster is used to fill and cut down on the absorption so they have a easier task for the finish coat.

It is not exactly like drywall, and it lasts centuries longer.

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Engineer, designer and consultant recently active internationally on construction and design in about 35 countries.

Wolverine-Eric

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POOLMANinCT

plaster not smooth or unworkable????

plaster can be pulled like silk....

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sumdry

Mud over concrete does't work. After a while it will show splotches of discoloration, then it will peel off. I'd suggest doing as the locals do and use materials they use. The right plaster can be smoother than drywall.

Brushslingers

Actually mud over block works ok, but the block needs to be sealed first, most times in your situation however, we just nailed 1/4 rock to the block after a good sealing and finished from there... cheaper.

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jbarcelos

Try using sheetrock over the concrete block, but first seal the block and use some type of vapor barrior(plastic), will be much less work, better finish and you save a load of money.rs..

mudgirl

Thanks to all who answered my drywall mud over block question. Knowing it won´t stick in the long run without pre-sealing is what I needed to know. I guess I wasn´t too clear, or some didn´t understand. The smooth finish I said I was looking for referred to the surface texture, - here they use a couple coats of mortar as a finish. They can screen the sand to make it finier, but the wall still is grainy, and hanging pictures, etc requires drilling and anchors. I was looking for something I could use that would be softer and not grainy. And the blocks are not really pumice, but they are not smooth, cast blocks, like in El Norte,they are concrete, but they can crumble fairly easily, depending on who makes them. As for drywall, it has become available down here recently, but I can assure you my crew wouldn´t have a clue how to hang it and would no doubt manage to break it before it ever got hung (and a flat, manufactured look is not what I´m after). But they can sling mortar on the walls quite quickly and labor here is not the big expense. ($1,400 a week, a case of beer and a couple roast chickens on Friday for 6 hard-workin´guys ain´t bad)