What Happens When You Have Rock Lath?

I have several long cracks in my ceiling and walls.

The House is a 1949 Cape Cod.  The backing is NOT lath but it looks like a cement board or another sheet of plaster.

Will Big Wally’s Plaster Magic work on this?

The plaster substrata that you have is called rock lath. The long cracks that you observe run at the border of the rock lath pieces. The rock laths are boards that are 16″ X 48″. The symptom that you see is typical of rock lath aging. It is not a very sound system. As your building moves the plaster cracks along these lines. There is nothing you can do to prevent this, you can only mask it. The good news is that barring other issues it shouldn’t fall down soon.

In order for Big Wally’s Plaster Magic to work it needs two materials to glue together. In this case the plaster is not delaminating from the lath making it a condition where the adhesive will not be useful. If the plaster is coming away from the rock lath or the layers of plaster are separating then you can use Big Wally’s Plaster Magic.

How long do I leave the Screws and Clamps in?

It’s important to leave the plaster clamped to the lath for a full twenty four (24) hours. Thia allows the adhesive to set completly. Remember clamp the plaster into soft contact with the plaster.

The adhesive shrunk into the holes overnight. Is this normal?

Short answer…Yes it’s normal…this allows you room to apply the joint compound when you are filling up the holes.

Big Wally’s Plaster Magic Stabilizes Plaster Better Than Other Methods

Be sure to watch our instructional videos at Big Wally’s Plaster Magic website.

When repairing plaster there are two major issues to consider.



Until the plaster is stabilized no repair will last. Once the plaster is stabilized almost any repair will last.

You test for plaster crack stability by:

  1. Placing one thumb bridging the crack
  2. Using the other hand press on the plaster on one side of the crack and then the other side of the crack
  3. If there is movement across the crack it needs to be stabilized.

There are four ways to stabilize plaster.

    1. Big Wally’s Plaster Magic is low odor, flexible, water based adhesive system designed to address the conditions found within plaster walls and ceilings.  Big Wally’s uses the wood lath or masonry lath to bridge the cracks and reinforce the plaster structurally. (In certain instances customers have used it to reattach plaster to wire lath.) Reattachment is accomplished by knowing the anatomy of the plaster walls and ceilings and using those existing elements assist in the repair. Big Wally’s Plaster Magic is flexible so it moves with your building. When using Big Wally’s Plaster Magic you do not need to apply mesh tape to the cracks, dig out the cracks (HINT: this actually weakens the plaster by ripping the internal fibers of the plaster), or apply anything to the surface of the plaster. Not doing these tasks saves half of the time of other methods.
    2. Screws and washers stabilize the plaster by compressing the plaster to the lath. Often this will crush the plaster further weakening it and only holds the plaster where the washer is. Screws and washers have rigid narrow point of attachment, only holding the area covered by the washers so you need LOTS of them. After they are installed they must be covered up and the cracks reinforced with tape or screening. This means either multiple layers of joint compound or plaster leaving a hump on your otherwise flat plaster.
    3. If you just use drywall tape (either mesh or paper) to bridge the cracks the plaster has not been stabilized except in a minor superficial way. All that has been accomplished is that the crack has been hidden for a short while; the plaster is still loose on the lath and moving.
    4. Using fiberglass sheeting or “wallpaper” to reinforce the plaster is just a surface treatment. The application is smelly, messy, and if you don’t like the texture too bad. You still need to use screws and washers (or BWPM) to stabilize the plaster if it needs it. It’s not cheap, not effective in the long term and if there is ever a problem with it there is no way to fix it.

    Big Wally’s Plaster Magic is the most cost effective method of plaster repair on the market today.

    Be sure to watch our instructional videos at Big Wally’s Plaster Magic website.

    After the plaster is stable the rest of your repair is cosmetic. How do you want your plaster to look?

    Customers Stories With Big Wally’s Plaster Magic

    We love to hear your stories. You, our customers have the greatest stories and give us confidence that we are on the correct path.

    This contractor was so excited to find out about Big Wally’s Plaster Magic that he drove 2.5 hours here from Boston. We would like to thank Nick for his story.
    It was well worth the trip from Boston to pick up your product. We used all of the tubes in the contractor pack and all the buttons (350 total) the walls were a mess.

    But not any more, the customer is happy and I’m happier, your product saved me at least a week of demo and sheetrock work.

    Enclosed are a few pics of the walls. And that’s my 75 year old father who founded the Company over 30 yrs ago.

    Dad helping out

    Dad helping out

    A don’t want to say what he said when we first opened up the walls, but his first comment the day after we applied Big Wally’s was ” Were was this stuff 30 yrs ago!”

    Thank you,
    Nick Hantzis, Owner
    Hantzis Home Improvements.

    Lime Washing and Finishing the Monumento de la Constitucion

    Day Six:

    Monday we started lime washing the monument. Before that happened we removed the burlap and plastic that protected the replacement plaster (render) as it cured.

    The south face in the morning sun

    Antwa (the man in the lift) started by lime washing the top piece of the monument from the lift. In the space of the morning Antwa applied two coats of lime wash to the upper part of the monument.

    Antwa lime washing the monument

    Antwa lime washing the monument

    After lunch we applied the first coat of lime wash to the body of the monument over the new and old plaster.

    Day Seven:

    This was our last day of production. I applied the second layer of plaster to the step between the monument and the granite blocks. Before the project is over one more layer will be applied.

    The final lime wash was applied to the body of the monument and the granite blocks received their first layer. Then we cleaned up.

    The monument before we started the restoration

    The completed monument

    Coenraad and Elizabeth invited me out to lunch (being the last day). It was quick back to the B&B for a quick change then off to lunch. On our way back to the plaza we ran into the project manager. He had arranged to have pictures taken for publicity about the Monumento de la Constitucion’s restoration. To say we were not camera ready was an understatement.

    As it turns out I was wearing the t-shirt I was given when I worked on This Old House, Newton 2007 . For those of you who are interested in history you might check out This Old House, Charlestown 2000. This was my first project with them.

    Coenraad and I posing for the finish shots

    After dinner one night I walked by the monument. Because lime wash is so luminescent I wanted to see for myself the night time glow.

    Isn't this beautiful?

    What a sight!