I’m a plaster enthusiast but I’m no pro. Soon I will be plastering my own bathroom remodel, adjacent hallway, and one wall in two adjacent bedrooms. I’ve had experience with using blueboard, diamond mesh, scratch and brown with Structo-lite, then a finish coat with White Kote. I went out to buy blueboard and it doesn’t seem to be available anymore. Now they sell something called Rock Lathe. This is a 3/8 gypsum material measuring 4′ X 2′, which is slightly larger than blueboard. I can’t tell if the paper is the same as old fashioned blueboard but it looks similar. Is anyone familiar with Rock Lathe? Would I be smart if I used a bonding agent such as Plaster Weld? Or is that unnecessary? Thanks for your help.
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Don't know how you missed rock lath in the past. It's been around since the 50's, maybe earlier.
My father did plaster for a bunch of years, alas, not much with me. I don't recall him ever using anything like the plaster weld you mention. Went right over the board. (I'm curious, does the stuff that you saw have round holes in it for the first coat to go through, or is it just a solid face like regular rock ?)
Don K.
EJG Homes Renovations - New Construction - Rentals
When they did my parents' house back ca 1965 I can't recall if they did a two-coat or three-coat job, but it was basically the same as regular plaster over wood lath.
Thanks for your responses... DonK, neither the blueboard that I'm familiar with nor the Rock Lathe have holes for the first coat. Since it's a solid sheet with nothing to key into, I want to be sure the plaster is going to stick to the paper on the Rock Lathe. Sounds like it should.
IMERC mentioned that he has done a good bit of plaster back in the day.
I don't know how to send a message direct to him to get his attention, but maybe he will see this and add.
Let's see, if it were me, I'd plaster right over the rocklath. Seems to me that's what it's made for and I demolished and patched my share of plaster over rocklath walls and don't recall seeing anything special about how the original plaster was done.
IMERC, what do you think?
"Let's get crack-a-lackin" --- Adam Carolla
Rock lath is 16 or 24x48".. 16" IIRC is the most common.
RL is the brown coat so you gray coat directly to that and then yur white coat over that... you can color yur white coat to what you wish...
apply the coats with at least a 24" finishing trowel and a hawk... learn with a 16/18" first... it'll save ya some work but it will not come out as well... you'll get ribs from the trowel edge but don't worry as long as they aren't radical you'll be able to float them out... I prefer a mag style with rounded edges and ends... mine is a 26"... finsh float with a Darby.. Here I prefer at least a 48" and 60" is better still 'specally if you large flat areas..... if you have a size 28 neck and arms to match do the floating with a 72"...
when you mud .. if you get tears and ripples or the mud doesn't want to cooperate it's too dry.. it won't stick well either.. if it wants to slide down the wall... too wet... it's too wet if it squeezes out from the ends and edges of yur trowel way easy or you get a high low surface (roller coaster) but you don't think you are changing working pressure at all or by much... bubbles and pits is too much pressure with yur trowel for the viscosity of the mud...
low humidity will make yur mud early and crack... predampen the surface a little bit.. as in a wee bit... with a spray bottle of water... lessen the water draw out...
rainy days are good days for this... but some extended dry time is to be planned for and expected...
RL can be installed inside out.. the errant piece will show up in the final next week or next month... but it will show... paint won't help...
we used bonding agent in repairs but never in new work...
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming
WOW!!! What a Ride!
Forget the primal scream, just ROAR!!!
Good post!++++++++++++++++++++++++++++++++++++++++++++++++++
"Doubt is not a pleasant condition, but certainty is absurd." Voltaire
but where's my check....
been since the early to mid 60's since I did that...
wish I could have forgotten...Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
Your check is the same place mine is: already spent. ROAR!++++++++++++++++++++++++++++++++++++++++++++++++++
"Doubt is not a pleasant condition, but certainty is absurd." Voltaire
that figures....
didn't even get to touch it...Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
Neither did I.Same ole... different day.++++++++++++++++++++++++++++++++++++++++++++++++++
"Doubt is not a pleasant condition, but certainty is absurd." Voltaire
Rock lath has been around in various forms since the 30's. I haven't seen it for sale anywhere around here for years, it's all blueboard now. You could use sheetrock with the backside out and treat it with a bonding agent like Plasterweld and then just go to town with the white coat, I've done many rooms that way. Or do it like you stated, it sounds like like you know whats's up. Imerc pretty much covered it. A lot of plasteres don't even know what a "darby" is anymore...a large float, they just use an aluminum screed and a 'slick'. I made my
own darby once out of cedar and it worked well.
To answer your question, I would say that you don't need to treat the rock lath, just put it up and do your brown.
You're using white veneer, not a guage? Whatever.
It's good to see people still plastering. Good luck.
My 1929 house has plaster over rock lathe walls.
Thank you again for the responses. Jer, can I pursue something you mentioned? You made the distinction that White Kote is a veneer, not a gauging plaster. To be honest, I never thought about it -- I just saw White Kote as a 'finish plaster' meant to go on as a very thin layer that is troweled smooth. After reading your post, I looked up gauging plaster and veneer plaster in my reference book, "Plastering Skills" by Van Den Branden/Hartsell. But the definitions don't say anything about how each material behaves. So now I'm curious. Does a gauging plaster trowel as smooth as a veneer plaster? Sandier? Are set up times different? The book mentions that gauging plaster can be bought in a 'slow set' formula. Would that give me appreciably more time than the White Kote I'm used to? Other factors -- The hallway has a slightly rougher, sandier texture with shallow irregularly shaped voids that I must match. The other rooms are much smoother. In all of the rooms except the bathroom, the new plaster meets the old plaster -- so that joint must be screeded flush, sponged clean, and futzed with to make as invisible a joint as possible. Any advice on which material would be most appropriate? Thanks for expanding my education in this.
> The hallway has a slightly rougher, sandier texture with shallow
> irregularly shaped voids that I must match.I'm vaguely remembering now. When they did my parents' house they finished a few rooms with a different finish. I'm remembering that through most of the house they did a brown coat, a sand coat, and then a finish coat. The brown coat was, well, brown -- cement-based, and left with a rough finish (though not scratched). The sand coat was more or less white but had a slight sand texture/color. The sand coat was used to achieve the required thickness/flatness (level with the plaster bead). The finish coat (pure white) went over that in a very thin layer, so you could see a bit of the sand coat showing through in spots.The rooms with the rough finish just had the brown and sand coats, and the sand coat was done as a sort of "dashed" finish -- splat the coat on, press it down smooth, but make no attempt to fill the voids. A bi*ch to paint.Ceilings, IIRC were just done with the sand coat, smooth (relatively speaking).
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
> and futzed with to make as invisible a joint as possible. Any advice
> on which material would be most appropriate?Vasoline on the eyeglasses works well.
If Tyranny and Oppression come to this land, it will be in the guise of fighting a foreign enemy. --James Madison
I'd have to be there to look at the material to say what to use. A guage is simply a mix with the white neat plaster (a coarser form of pop) and a fine lime putty. Lime has to be soaked or 'slaked' for at least 24 hours in water mixed in the right proportions to make a plastic-like putty. Typical flatwork takes a 3:1 ratio of lime to plaster mixed in the classic 'ring' of lime and water that we all have seen done. There are retarders added to the water to slow the set of any quickset type of plaster. Plaster setting depends on how you mix it, the ratio, any retarders, the humidity and temp of the room etc,. and even the age of the plaster. Plaster does not have a good shelf life. There are many different types of plaster in white and grey, some courser than others and some with different hardness.
White veneer coat, like Kalcoat or Diamond coat is simply plaster with other aggrigates & additives to give it a workability the same way the lime putty does. You can retard the set if you want when you mix it with retarders mixed in with the water. Roughness and texture depends on what you're using and how it's being trowled. The lime finish can be wet trowled and polished to an actual gloss finish, somewhat like encaustica, marmorino or Venitian plaster. It's quite beautiful actually when a pigment is added.
Plastering is a skill in which timing is everything, knowing when to go back and spatter and 'sweeten' a wall with a fine wet mop and steel trowel or as Imerc mentioned about when and how to float the base coats.
Blueboard should be available, at least by special order from wherever you get sheetrock. Working with 4x2 sheets would be easier but seems like more trouble to me.
If you use sheetrock, and USG Diamond Finish veneer plaster, you can use the USG primer for the board, and do not need base coats, just a veneer coat of Diamond directly on the board.
Typically you only need a bonding agent on a surface that is too 'hard' for the plaster to adhere to. Paint, the front face of regular drywall, plaster top coat that is cured are common examples. There are bonding agents that you paint on the surface and ones that you mix in water that you use for mixing the plaster.
My impression is that blue board is designed for a single layer of something like Diamond Veneer top coat, while rock lath is a substitute for wood or metal lath.
Heed what IMERC said about Darbys. That will be the difference between a good job and one that looks like I did it.
Good luck! Post some pictures.
My impression is that rock lath is a substitute for wood or metal lath.
and the scratch coat of a three coat process...
note.... adding binders to the mixes can marble the final showing (as in something else to take care of) and give you multiple viscosities wthin viscosities that can make extra work and leave something to be desired in the final ... same for painting on too much of it or mudding over it while it is plenty wet....
Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
Terrific information... again, thank you. I read up on Gauging Plaster in my book, Plastering Skills, and even though this is much more involved than simply adding water to a bag of White Kote, I really want to give it a try. If the results aren't totally humiliating, I will post pictures.
look at it as you could have a uniquely textured walls...Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming<!----><!----><!---->
WOW!!! What a Ride!<!----><!---->
Forget the primal scream, just ROAR!!!
>>"I really want to give it a try.
Best of luck. If you do a lot of work on old houses, it is worth its weight to learn how to do.
Just as a well done paint job can often turn some sow's ears into silk purses, knowing how to replaster and repair plaster can turn what looks like an unsalvagable dump into a pile of gold in very little time.
"Let's get crack-a-lackin" --- Adam Carolla
I believe the book you have is the one we used in the plastering union way back when to teach from, and they still do last I knew. Put out by USG.
If you live in or near an older city like NY or Boston, there will always be plasterwork to do. Once you get the flatwork down, try some historic finishes and then ornamental work like cornices and castings.
Putting on too much, that's where I went wrong. I should have done another coat of structolite.