Cracking up – notes on prepping for Venetian Plaster and Lime Finishes in general.

Posted on June 2, 2009 by Aaron Cohen
Cracking up – notes on prepping for Venetian Plaster and Lime Finishes in general.

Here are the 5 biggest issues I see out there concerning prep work:

1 - Stop the cracks – Can you do an exterior?  Sure!  Can you do a shower?  Sure!  But you gotta stop the cracks.  So you have to know what you are doing.  Or hire someone that does.  And a very important point to bear in mind – lime does not crack by itself.  But it cannot bridge cracks. It adheres to whatever substrate it attaches to.  So when the substrate cracks the lime plaster cracks with it.  And never promise a crack free finish because if you do not actually do the substrate construction and preparation how can you guarantee the thin veneer of decorative plaster we apply will hold?  This often falls outside of our area of expertise and responsibility.

That being said, EIFS mesh and primer systems usually work pretty darn well, in my experience.

2 – Penny wise pound foolish  (AKA prep with the good stuff, you’re worth it!) – So you gotta fill a wall that has orange peel texture because you want to run a nice shiny plaster over it.  So you get out the joint compound because it’s cheap.  You skim.  Then you sand.  Then you prime.  Twice.  Then you can apply your lime plaster.  Hey but wait a minute, why didn’t you just skim with our Marmorino Classic and then do your finish right over it?  Because it’s so damn expensive you say?  But think about it -  if you skim with the good stuff you’ll already have your first coat of lime plaster on.  You’ll have the proper suction and you can do your final coats the next day.  The money you spend on materials (joint compound vs lime plaster) should be more than offset by the money you save on labor, no?

3 – Scrape don’t sand – Got some excess gunk on the walls before you start?  Or did you get some trowel lines from your first coat?  Before you throw up the giant cloud of dust with that sandpaper try breaking out a putty knife and scraping.  Less work, less dust, more better.

4 – Taping – it’s not paint – Yes it’s not paint so don’t tape right up to inside edge of where your wall meets your baseboard or crown molding or whatever you are protecting.  Otherwise you’ll bury your tape underneath your plaster and it will chip or crumble off when you remove your tape.  Allow for the thickness of the plaster material you will be using and tape away from the wall by 1/16″ or more depending on what material you are using.

5 – Do not assume the people doing your prep are going to do it properly.  Unless they work for you. And then only if you know what you’re doing.  Which is debatable.…

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Exterior Distressed Lime Plaster

Posted on April 18, 2009 by Aaron Cohen
Exterior Distressed Lime Plaster

Exterior Distressed Finishing:

This can be particularly challenging as we are generally trained in life to create uniform patterns and you have to break this habit to mimic the chaotic patterns we see in nature. I’ve seen some really awful work out there and it is generally a result of poor composition. It’s easy enough to make a 2×2 sample board look natural, but how can we do this on a much larger scale?

Here’s some tips on how to achieve randomness in your distressed finishing:

1- Study actual photos of crumbling plaster exteriors and interiors. Note the size and scale of the different layers, note the shapes and direction. I generally work with about an 80% vertical and 20% horizontal direction, very little or no diagonal direction.

2- The pattern on a sample board must be expanded to the size and scale of the walls. A sample board may be viewed as a miniature version of the wall to be blown up accordingly.

3- Move your body in a large scale. That is, be expansive, move your arms accordingly – don’t work with small, tight motions from the wrist or elbow. Instead work from the shoulder. Stay loose.

4- Create pattern over multiple layers, not just on your final layer. This will force a greater degree of randomness in your overall pattern. Here’s an example:

On this exterior project the client really wanted to see dark brown openings through a Terra Cotta finish. This created a finish with a high degree of contrast so we had to be particularly careful about not allowing the house to have a contrived pattern when completed. We needed to do the finish in two coats since it was a large exterior surface – approximately 20,000 square feet. Rather than cover the entire first coat with the dark brown we chose to cover only about 15-20%.

This “under-pattern” was designed to help the stucco installers find a more realistic shape and scale on their second pass of material. Also, note how the dark brown generally originates from the top of the wall or the sides. This is often what you will see on an actual stuccoed surface where the first coats of plaster are falling away from the surface. Kind of looked like a giant cow for a while and the country club’s community board got a little nervous, but fortunately our clients had faith in me.

This photos shows the work in progress on the 2nd layer: The dark brown is revealed in small, linear shapes beneath the 2nd terra cotta stucco layer. By following the pattern initiated in the first layer, we had a much easier time avoiding the contrived, obvious, unrealistic pattern I was concerned about.

And here is a detail of the finished exterior surface.

Final tip: PRACTICE!! On a 4×8 sheet of drywall, or your mom’s house. You’ll get the hang of it. Just don’t try to figure it out on a multi million dollar job site if you can help it. Unless you have nerves of steel. We don’t.

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