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Sheetrock?


SNelson's Avatar
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Join Date: Aug 2002
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08-21-02, 07:30 AM   #1  
Sheetrock?

OK, I admit... this is a really stupid question. My house was probably built in the late 50's/early 60's. I always thought the walls were plaster because I can't see any seams. We installed a new ceiling light & now that I see the stuff, I'm not so sure it's plaster. It doesn't look like any of the wallboard they have at Home Depot. It has a paper backing, with a layer of grayish, crumbly stuff with plaster on top. There isn't any mesh or wood lathing behind it that I can see. What is it?

 
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coops28's Avatar
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08-21-02, 08:02 AM   #2  
Starting in the 40's they did away with wood lath. Instead they used sheetrock lath. The sheetrock came in 2' by 8' sheets. They applied the sheetrock to the wall then plastered over it. It wasn't until the 60's when they started using drywall as the final coverage.

 
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08-25-02, 06:22 PM   #3  
A little info to help or maybe confuse.

Drywall: Also known as sheetrock, wallboard, or gypboard. The biggest part of the gypsum rock used in this country goes into wallboard for homes. Drywall is formed by sandwiching a core of wet plaster between two sheets of heavy paper. When the core sets and is dried, the sandwich becomes a strong, rigid, fire-resistant building material. Fire-resistant because in its natural state, gypsum contains water, and when exposed to heat or flame, this water is released as steam, retarding heat transfer. Drywall is simply cut, butted together, nailed to the wall studs, and all seam areas and nail holes are finished with joint compound creating a smooth uniform appearance.

Plaster walls: Before 1900, lime-based plaster was used. It was mixed with animal hair and sand to give it stability and strength. After 1900, a gypsum-based plaster was used. A three-coat system was used in either case. First a scratch coat, which was pressed into the lath to form the plaster "keys" to hold it in place. Lath boards are the series of boards nailed to the wall frame spaced 1/4" apart. This spacing allows the scratch coat to mushroom between the gaps and anchor the plaster in place. This is followed by what is known as the brown coat, which is the first step in creating a level surface. The finish coat is toweled under pressure until the surface is mirror smooth. Lath boards are usually wood, though they can be metal in commercial applications due to increased fire resistance. Buttonboard plaster came into use in the 1950s. Buttonboard is a 3/4" thick material similar to drywall with numerous holes in it to serve the same purpose as the spaces between the lath boards. Only two coats of plaster are applied to buttonboard. The last type of plaster is "blueboard" plaster. This is drywall with a blue facing paper. The drywall is installed as normal and then one skim coat of plaster is applied to the entire surface.

How to tell the difference: The easiest way is to remove an electrical outlet cover, if the wall is more than 5/8" thick, it is plaster. Most modern houses are drywall though there are exceptions.

 
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08-26-02, 07:12 AM   #4  
Huh????????

 
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