interior walls plaster?

[kimball gray]

house built in the 50's. the owner says the walls are cement. they look like cement. In the hot water closet I found an exposed area where damage had occured. You can see wire mesh behind the materil and no laths. What is it?

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[hausdok]

Interior Portland cement stucco.

ONE TEAM - ONE FIGHT!!!

Mike

[Mike Lamb]

That looks pretty much like plaster on metal lath to me. What's the tip off that it is stucco?

[kurt]

I guess you could call it stucco if you want.

I thinks it's standard metal lath plaster. Portland scratch coat on the metal lath, gauging plaster on the scratch.

[kimball gray]

I appreciate your replies. Thanks to your timely help as always.

[John Kogel]

house built in the 50's. the owner says the walls are cement. they look like cement.

Cement is the main ingredient, but the product is plaster or stucco.

Add gravel, it becomes concrete. That's how I keep the terms straight, anyways.

[Marc]

house built in the 50's. the owner says the walls are cement. they look like cement.

Cement is the main ingredient, but the product is plaster or stucco.

Add gravel, it becomes concrete. That's how I keep the terms straight, anyways.

I thought 'plaster' meant gypsum. Stucco is cementitious unless it's polymer based.

Marc

[hausdok]

That looks pretty much like plaster on metal lath to me. What's the tip off that it is stucco?

I always thought that plaster was made with crushed seashells and lime or some such and that it was white and creamy. Most plaster walls I've seen were gray when troweled on but dried to a nice white color not much darker than drywall. They looked much lighter that the stuff in that picture and had a very fine texture to them.

Stucco on the other hand has always had a courser component to it and a much darker hue than the interior plasters I've seen. I've seen plaster used with wire lath before but never plaster with such course grain or such dark coloring. It looks exactly like the broken stucco I see quite often around here.

That's why I thought it was plaster. Since I haven't worked with a lot of the stuff, I'll bow to Kurt's superior knowledge of the stuff.

ONE TEAM - ONE FIGHT!!!

Mike

[John Kogel]

Most old plaster I see from the back side, the brown coat, has a grey look, but they added a sand filler to it.

AFAIK, plaster can be gypsum, cement or lime based, it's all plaster.

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I'm no expert, but I gather Portland refers to a cement base.

[Bill Kibbel]

Kurt's got it right. By 1950, Portland cement was being used for almost all scratch coats. The final product is still called plaster.

[kurt]

Plaster's just a general term. It can be gypsum, lime based, or portland cement.

"Plaster of Paris" is derived from the ancient gypsum deposit in Montmartre. It's still just gypsum plaster, although I like the idea of plaster from Paris.

Lime plaster has problems, mainly that the material has to be kept in sealed containers and protected from air, or it sets up (exposure to C02 causes the calcium hydroxide to turn into calcium carbonate). Then, there's all the logistical hassles of slaking, etc. It's very time consuming.

Gypsum is pretty easy stuff. That's why it's popular. That's my opinion, anyway.