plaster vs. drywall

Questions and answers relating to houses built in the 1800s and before.

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Greg
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Post by Greg »

Everyone makes good points and each situation is different. I won't condemn anybody for putting in sheet rock. In my case I'm going to keep the plaster for a few reasons. First, I don't need to insulate because although it does get cold here it doesn't get really, really cold. Temps rarely drop below freezing and snow is a once every 100 year event. The amount of work and money involved to rip out plaster, insulate properly, and install sheet rock would never be recouped with lower heating bills. I will insulate the attic and do my best to stop air infiltration on exterior walls. This should do a lot to stop the chimney effect of loosing all the heat out the top of the house.

Right now the plaster in my house is in rough shape. However, when you considering that the plaster is 110 years old, the house was a rental property for 85 years, and has been through countless major and minor earthquakes over the last 110 years it actually looks pretty good. I really don't think sheetrock would have held up this well. You can find popped sheet rock all over this town after 5.5 earthquake.

The plaster on my walls is applied as a one stage lime and sand plaster, or so I've been told. It does not have a smooth finish coat. It seems to be very stable. The places where it is bad is were the POs but up plywood instead of stripping wallpaper. It seems more pragmatic to repair what is there than to take it out and hope that sheet rock will hold up better. I wish I could find out how to do lime and sand plaster work but as it is I do repairs with gypsum plaster.

My house also has solid wood walls behind the plaster as opposed to lathe strips. I was able to mount metal boxes with out a problem and fishing wires through walls was really not that hard.

As for cracks, there is no reason you can't tape them just as you would a sheet rock seam. Tape them before you skim coat and I’ve been told they won’t reappear. I've only done a complete repair job to the plaster walls in one room so far. I've gotten 2 very fine cracks that run vertically up the wall. They are so fine that unless you are standing right in front of them you can't really even see them. I would like it if they weren't there but it doesn't really bother me. I think they were my doing when I was removing an addition that was up against that wall.

Finally, the last reason I'm going to keep and repair the plaster is because I like plaster walls. I think it is one of the defining characteristics of an old house - cracks and all.

Guest

Post by Guest »

Sioux, I guess I'm not following you then, it sounded like your repairs were re-cracking but then you said the repairs have held up. If you are just mudding over the cracks then yeah those will recrack, no suprise there. They need to be either widened and taken down to bare lathe (in an inverted V shape), brushed w/ bonding agent, and then filled w/ plaster. OR the tape method. The former is my preferred method, quicker & easier. Taping gets tricky with having to feather out the mud topcoat to conceal the edge of the tape. (Or alternatively, scrape paint/ wall surface down 1/8 inch or so, so mesh tape can be embedded below surface of wall, then mudded over)

Yeah Im with you Greg, I just love the whole feel and esthetic of old plaster. There were people telling me I should tear my plaster out. I figured though that the walls had held up for 100 yrs and that by repairing I could get them to go at least another 20... or 50, or 100. I'm expecting that I'll just need to do some patch work every 10 yrs or so when I repaint.

Have heard that paintable caulk can be used in some situations--has some flex for those seasonal shifts. I've used it in places like along a chimney, between brick and wood lathe. ( oops I confess there was that one spot that did recrack, becuase the brick and the wood expand/contract at different rates.)

Oh one last thought, seems I read somewhere that it can be determined what's causing the crack on the basis of what the crack looks like, what direction its running etc. But dmned if I can remember where I saw that. Definitely worth determining CAUSE of the problem before undertaking something as extensive as complete drywalling.

SiouxCItySioux
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Post by SiouxCItySioux »

correct, the new repairs are holding fine, it's the old hairline cracks coming back. which, is understandable, since i just covered them with mud during skim coating.

in the beginning, i considered widening the cracks and filling in with mud, but there are just so many, i may as well pull the entire wall down because it would practically all be new then. :)

i just got finished trying a little experiment in the dining room (the most recent repaired walls). i took some of the wall paint and "forced" it into the cracks and then feathered the paint out into the existing surface. the hairline cracks are still there, but they don't stick out so bad anymore, since they are the same color as the wall. this may be what i'm going to have to do because i just hate the idea of losing my plaster walls.

the only thing that still bugs me is the vapor barrier issue. if i didn't live in the midwest, i don't think i would worry about it (as greg described). i just wonder how much moisture actually gets through the 2 to 3 coats of paint (satin finish), the 2 coats of "first coat" primer, the skim coating, and then the plaster itself? if the amount is significant, that would be a problem, in my opinion, and i think i would have to give up the plaster walls and go with what will preserve the structure of the house.

is there anyway to actually find out how much moisture is in the walls? besides those expensive moisture probe devices that inspectors carry around, of course.

Nancy W
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plaster vs. drywall

Post by Nancy W »

I have heard of successful repair of hairline cracks by covering the crack with MESH drywall tape and the mud. The crack may still be there but the mesh tape hides it and perhaps has a little flexibility in joining the two sides of the crack together.and will accomodate the seasonal changes better.

Bryan
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Post by Bryan »

SiouxCity Sioux,

As far as your vapor barrier question, I remember reading somewhere that a certain amount of paint will act like a vapor barrier, but I can't recall how thick. It makes sense that after several coats of primer and paint, you essentially have a vinyl barrier which should act the same as the poly barrier which would be behind your walls. I believe it was on the DIY Network show, Ask Jon Eakes. Anyon else heard of paint being a vapor barrier?

Bryan

Dave
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Post by Dave »

I've read in numberous places that latex paint is permeable to vapor and oil based paint retards moisture.

Latex are generally more transparent to moisture than alkyds allowing water vapor to pass through. This property of allowing moisture to escape through the paint can help prevent pealing from exterior wood surfaces as where a moisture resistant coating may blister as moisture passes through to the exterior.

and

top-quality 100% acrylic latex primers and paints offer...Breathability: The ability of a coating system to allow natural moisture within the wood to escape as moisture vapor, without causing the coating to blister or lose adhesion. Moisture which can not escape leads to loss of adhesion of the coating

these are from the first two google hits using vapor, latex, oil as search terms. I think I have read somewhere that vapor barrier paints are available to buy. I dont think that acrylic latex is the same composition as vinyl

Dave

Greg
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Post by Greg »

There are products that can be used that say they will create a vapor berrier.

This is from the Univ. of Mass site on building technology
Here again, product literature can be misleading. Some manufacturers may list hydro-head test values like "186 cm." This is the height that the water column reached before the material began to leak.

One tested value that actually can be compared between brands of housewrap is vapor permeance, which is usually tested according to ASTM E 96, with the results expressed in perms. The higher the value, the more permeable the material. (A material with a perm rating of 1 or less is considered a vapor barrier.) Unfortunately, the wide spread in perm ratings among brands -- from 5 perms to over 200 perms -- makes it a little difficult to assess the importance of this number. The codes require wall wraps to match or exceed Grade D building paper, which has a minimum perm value of 5.

To complicate things, the permeance of felt paper is a moving target. Felt paper absorbs water and ranges from a low of around 5 perms when it's dry to over 60 perms when it's exposed to relative humidity above 95%. The perm values of engineered wall wraps, however, are moisture-stable. Although high permeance is generally desirable in a wrap, excessively high ratings are not as important as resistance to air and water.
Note that it says that A material with a perm rating of 1 or less is considered a vapor barrier.

Behr has a PREMIUM PLUS® Interior/Exterior Oil-Based Primer & Sealer No. 43 that says when you apply 2 coats it claims to meet the requirement of a vapor barrier (As a vapor barrier, this product has a Perm Rating of less than (1.0). Apply two coats.). I think Sherwin Williams makes one as well as others. Of course, you still need to deal with where the wall meets the trim and around outlets and switches. Someone in another forum said they have used shellac in these areas before applying the top coat.

guest

guest

Post by guest »

Maybe its your technique (materials you are using, etc.) or you are trying to repair a bad plaster job to begin with. My own exp. I have repaired large plaster areas and cracks (1899 Vic)using setting type compound- its going on 9 years without a crack. I live in the NE(CT) where we also get large temp. swings.

SneezyDec
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I vote for plaster

Post by SneezyDec »

Me, I like plaster better than drywall. We are going to be replacing about 90% of our dining room with plaster (using the three coat method). Its not that hard to do once you get the hang of it, and, after having repaired the living room walls, I have to say that they are so solid I can't imagine they will be going anywhere or cracking for a good long time.

Our dining room has one side where the POs put up drywall, and the other side has plaster on it, so its a good comparison. The side with plaster needs to be patched, no doubt - its completely missing in some places. But the side with the drywall is also in rough shape - regardless of what we'd use to redo the walls, it would have to be taken out.

I vote to plaster!

SiouxCItySioux
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Post by SiouxCItySioux »

greg,

thanks for the info and links. that's some helpful information.

guest,

when you say "setting type compound", is that the same as drywall joint compound? the technique i use is i buy the dry joint compound, 5 type for the larger repair areas, and 30 for leveling and smaller repairs. then when the repairs are built up to the surface of the surrounding plaster, i use the premixed joint compound to apply several skim coat layers to make the walls completely smooth and level.

these repaired areas seem to be ok. the large ones, at least. the cracking only seems to occur where the skim coating is (where there were hairline cracks in the walls before). so, i'm thinking there's no way around it unless one tapes all the cracks and floats them out, or digs them completely out and refill, as others have suggested. but, then i'm also thinking that plaster is much more rigid than floating tape and joint compound so if the walls expand or contract, the crack is going to reappear somewhere. even using the mesh type tape, i would think the natural movement of the walls would have to give somewhere, most likely the weakest link, which would probably be the joint compound.

they aren't large cracks, they are just hairline (i don't think that you could even fit a razor blade into them) but, i am a perfectionist :( and i think that i may have been overreacting a bit (in the dining room, there were 3 hairline cracks, maybe 1 foot long). after applying paint to the cracks over the weekend, they don't stand out anymore. on the lighter colored walls, the cracks showed up as dark lines, where on the dark colored walls, the cracks showed as white lines. i guess i just have to learn to accept these as part of owning an old home and just apply paint to wherever new ones appear.

sneezydec,

where do you get your plaster to do your repairs? i have not been able to locate it here. maybe i'm not referring to it by the proper name. we have a menards and we just got a brand new lowe's. is this something you have to special order or go to a specialized store for?

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