1: DRYWALL
is the process of finishing wallboard joints and fasteners with multiple coats of joint compound. In some cases a skim-coat of specially prepared joint compound is used over the entire surface for a higher quality finish product.
2: VENEER PLASTER, also known as skim coat is a complete coat [nominal thickness 3/32in.]of gypsum plaster over a wallboard with specially treated paper which aids in the working characteristic of the plaster.
3: MULICOAT PLASTER (2 or 3 coat) is used mostly in commercial work and in some special situations for residential application such as curves which may be too tight a radius for wallboard to bend.
When I first got started in construction I was doing drywall for a few years believing, as my mentors would have me, that only a fool would waste his time with plaster in this day and age. Drywall was quicker, easier to learn and do, and cheaper than plaster. Of course I was a bit more naive then and just didn't know the facts. Living in an area where many of the homes were built before our country's Revolution it was easy to say "Yeah, look at all the cracks and bulging plaster on that wall, you wouldn't get that with drywall". Well having been in the trades for over 30 years now I've seen a lot of new construction that is already destined to be replaced. Honestly, how do you think today's drywall will look in the year 2200.
In my business, on a yearly basis, I will do approximately 50% new construction with the remainder split up between old horsehair restoration and drywall repair, constantly taking phone calls asking if nail-pops and bad joints can be repaired and yes, they can.
a : Drywall is quicker.....FALSE
A typical home takes about the same time to complete given drying time and recoating compared to plasters' one coat, DONE.
The only thing that makes drywall a faster product is the fact that it can be painted as soon as it is dry (usually the next day) with an oil based paint.
Plaster needs to cure a couple of weeks unless water based paints are used in which case the next day works.
b : Drywall is easier... OK, you have me there.
I can teach basic drywall finishing to just about anyone in a day and let them work on improving their technique over time, however it takes months to
train someone in the proper use of a trowel and in some cases, a couple of days just to get all of the plaster from the hawk to the wall.
c : Drywall is cheaper.... Initially maybe
The cost difference between drywall and plaster is comparable to what I charge to repair those drywall jobs after as little as 3 years so factor that into
a mortgage and tell me it was worth the initial savings.
People let their building contractors talk them into exotic bath fixtures and Italian marble. Custom kitchen cabinets and solid granite countertops. Beautiful
lasting hardwood flooring. And then they pass off drywall as an acceptable wall and ceiling system.
I personally know builders who admit the customer just doesn't know the difference so why bother.
Q: My walls have plaster over cinder block and stucco and it keeps cracking under my windows and over the doors. I have tried sheet rock mud with mesh tape, but it does not last. Do you have any recommendations on how to repair?
I live in a old house and there is no wood in my exterior walls. Q:
Hi, my husband and I are building a SIP panel house in PA. I was wondering if I could plaster the interior walls--or if there was another material I could use other than drywall? Thanks so much for you attention and response. Q:HI,
We are looking to cover painted cinder block with a layer of plaster and then paint over that... perhaps even with a rough looking finish or a sanded smooth finish - not sure yet. Is there a special compound we should be using? or is it plain drywall mud? Q:
I looked at your website after seeing some of your responses on the This Old House website. I've got a 1906 house in rural Eastern Washington State we've been renovating for over 8 years. I'll confess that we removed all lath & plaster on the first floor to wire & insulate and replaced with sheetrock. I'm now working on the stairwell and upstairs hall. No need to remove the plaster, but it needs help so I'm researching giving it a fresh coat of plaster. One small exterior wall we did have to tear out to insulate. So, I have a combination of old plaster and some drywall that I need to coat. Incidentally the ceiling seems to have a rather thin single coat of original plaster and the lath is quite visible under the plaster.
I just read that you recommend Blueboard instead of regular sheetrock... too late for me.
Can I plaster over everything (including some areas that have sheetrock mud)?
Do I first need to tape the joints on the new sheetrock and finish with sheetrock mud?
Do I apply the bonding agent to everything? Old plaster as well as sheetrock?
The bonding product I bought indicates it should be dry for new plaster mixes, but tacky for Gypsum plasters and finish plasters.
I'd be grateful for any guidance! Q: I want to use a drywall joint compound to create an aged-Moroccan looking wall over a cement block wall that has been painted (not recently, but paint is in great shape).
this is in a covered screened porch area in central Florida. it will not be directly rained upon or in the bright sun, but it is not in AC either.
Can I use drywall joint compound mud? do I have to prime it with a bonding agent? can I use Kilz ? Q:
Hello, We own a 1912 brick home that still has it's original "horse hair" plaster. We recently hired a "plastering" company to repair the stress cracks, some holes around the molding & door/window frames and to remove the areas where the plaster was loosening from the wood lattice. They "skim-coated" the entire walls.
Just after the job was complete, I was informed that there were several problems with the job.
They included:
1: Plaster (which was actually joint compound) overlapping the tops of the baseboards in several spots. answered in numerical order
1: Material overlapping the baseboard is unavoidable to get a tight finish but is easy enough to clean off (contractor responsibility).
Thanks for any help,
MB 1/24/08
A:
First I have to ask if the Sheetrock® mud was a setting compound or straight from a bucket. Mesh tape should only be used with products such as Durabond#® or Easy Sand#® which are setting compounds as there is no structural strength to ready mixed types. If you used the wrong product simply clean out the cracks and try it again. What I would do, which unfortunately is not a do it yourself task, is: lay up the entire surface with fiberglass mesh, which comes in 36" rolls (looks just like the tape), roll on a bonding agent and replaster the wall/s.
Best, M W 02/03/08
A: Great choice! Stressed Skin Panels, as we call them in NH, are commonly used here in post and beam construction and create a very tight envelope for your home. Apart from their insulating qualities they make easy work out of installation of wallboard on exterior walls and cathedral ceilings in that type of construction (exposed beams and bracing). Although I don't know the availability in your area or the arrangement you have with your contractor, here in New England we can order the panels with either regular wallboard for drywall, or blueboard for plaster. I have worked with both and in situations where the builder used regular panels by mistake (not researching beforehand as you are doing) I've been able to bond and plaster the surface anyway. While the finish comes out quite nice it still doesn't meet my usual standard of quality. I supppose I should explain some characteristics of the plaster first. Blueboard is different in the sense that it is absorbant. When we mix a batch of plaster there is a working time to deal with averaging one hour. A coat of plaster is laid out on the wall or ceiling about 1/16th of an inch thick and then another coat from the same batch is doubled over it again. That first coat stiffens up considerably because the water is being sucked out of the mix thus allowing the double over. This is what gives us the workability to remove the trowel marks and eventually polish it smooth to a glasslike finish. When a wall must be bonded a gluelike liquid is rolled on first. This guarantees a good bond to many types of surfaces but unfortunately ruins the working characteristic of the blueboard. The plaster doesn't stiffen until the mix is ready to actually set up which leaves very little time to work it smooth.
Thanks, R W 02/23/08
A: Hello R,
It's not that difficult a task if you're not looking for smooth perfection, I probably do it a dozen or so times a year. First you need to roll on a layer of concrete bonder. There are two general types so be aware. One allows you to roll it on and come back whenever you are ready while the other requires you do your plaster coat within an hour or so while it's still tacky. If you wait too long with the second it actually act as a release agent and you certainly don't want that. You could use a setting type of joint compound and omit the bonding agent but it would be very costly and redimixed mud is out of the question. Hopefully the is a supplier in your area for basecoat plaster either USG® or National Gypsum®. My preference is USG Basecoat Plaster® and it comes in 50# bags. It has a working time of around 45 minutes. Unless you have plastering experience you should not mix more than half a bag at a time. If you wanted a smooth finish you could do a second coat with Diamond Finish® or Imperial Special White® but again, unless your a trained plasterer, smooth is not really a viable option.
I hope this helps you.
Thanks very much! Chewelah WA 03/22/08
A: The answer to everything asked here is yes. Just be sure the underlying surface is sound and not wood. I've had clients ask if I could plaster over paneling and other wooden surfaces and the answer to that is a definite no. Wood {except lath, which is spaced to allow keying of the plaster} is highly suseptable to moisture and movement which makes for a terrible base. Next, I would also point out that any taping and filling should be done with a setting type compound. Ready mixed joint compounds are water soluable and will deteriorate under the wet plaster. As for the directions on the bonding agent I am confused. The product should be more specific as to the type of plaster. By definition plaster can be made of almost any paste that can be spread on a wall ranging from portland cement to gypsum. To say "new plaster mixes..." is basicly incorrect since 99% of plastering done today is gypsum based.
Thanks!~
Marla E
marlae.com 4/20/08
A: Well to quickly answer Marla's question I'll just refer to a couple of previous questions above. I'm not a big fan of ready mixed joint compounds for anything other than drywall finishing and texturing so I will never put my stamp of approval (as if anyone really cares) on using it over block. Kilz is a stain sealer and primer, better than some, not as good as others. It's all a matter of preference and, like any good sealer, suitable under joint compound. Bonding agents are used for bonding a layer of plaster to any stable surface but not required for joint compound. A note on joint compounds: A bucket of joint compound is made up of acetates and polymers and other stuff that are simply fillers which when air-dried make a nice soft finish suitable for sanding smooth or texturing. There is no strength to it which is the reason you should never use it with mesh tape. Setting type joint compounds, on the other hand, are made up of polymers and plaster of paris which when wetted begin a chemical reaction resulting in a hard, durable finish. These come in 25# bags with setting times from 20 minutes to 4 or more hours, enough for any novice to handle.
2:"Air holes" all over the walls.
3: Larger holes here and there.
4: Joint compound applied directly to the door/window frames from the wall instead of caulk (which was lumpy).
5:Mesh tape applied right up to the frames and sometimes protruding out of the plaster.
6:Large defects (that look like large valleys) between the wall and the molding.
7: Joint compound used instead of gypsum plaster.
8:Some parts of the corners were rounded, instead of coming to a sharp point.
9: Some areas that were caulked were very lumpy and bumpy.
So my questions are: Is gypsum plaster (Durabond - correct??) a better quality, longer lasting product than joint compound (b.t.w., the first layer was grey & the final layer was yellow)? Can these problems be fixed by a skilled plasterer? And if so, what will they need to do to correct the defects?
Thank you!! K. 12/26/08
A:
Where do I start?
First off, I guess we'll address what was done. Whether or not they were actually a "plastering" company, it seems they just did an all over skim with Joint compound which isn't unusual these days. It's not how I would have approached it but not necessarily wrong. What is wrong, however, is how the job was apparently left. The problems you mention aren't material related but rather the fault of sloppy workmanship.
2:
Air holes are the result of suction from the dry old plaster. Moisture is drawn away from the mud (joint compound) so rapidly it leaves tiny blisters. These should have been polished out of the finish. Sanding them only cuts the top off leaving open holes.
3: I'm not sure what the larger holes are here and there. Could they have been holes in the old plaster that weren't filled? Send me photos.
4: Again, I'm not really sure what you mean about the frames.
5: Mesh tape should be used up to the frame to hold the new material firmly in place but not left to be visible in the finish.
6: Large defects are just that. These guys sound like they need a bit more experience.
7: Joint compound is commonly used, often rolled on and is a method used mostly by drywall contractors. I usually use a sanded gypsum plaster
over a completely meshed wall. The fabric is stapled right through the plaster to the lath and the whole product is polished slightly to recreate the original finish. This is, however, a repair and not a restoration as horsehair plaster is not the same plaster we use today. Everything used in modern construction is gypsum based. Horsehair plaster is almost exclusively hydraulic lime.
8: Rounded corners are one of my pet peeve's which is why I've been working alone all these years. That's my quality control.
9: Last but not least you simply got a bad crew.
As for your questions, Durabond® is a setting type joint compound not gypsum plaster. It contains 'plaster of paris', which in itself is a gypsum product,
and acetates. It's much harder than redimixed joint compounds and is an excellent product for the type of repairs you were looking for, unfortunately your's was done poorly by what you described. Both JC's come in a variety of whites due to manufacturing differences and have not bearing on the finish.
Can they be fixed? Sure, I haven't found a problem I couldn't fix but then I don't know where you live so I can't tell you to just give me a call. You should go to a reputable supplier and see if they can recommend someone who's been buying from them for a decade or more. (And by supplier I surely don't mean one of the orange or blue superstores out there, if you know what I mean.)
