Vertical Overlay principles

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I have done a shower surround with cement board and a polymer modified mix.

What are the basic principles of doing vertical overlay?
When and why is a scratch coat necessary? This is one concept I don't quite understand.

Why wouldn't one want to do a one coat overlay on top of existing drywall?

itsreallyconc's picture
a scratch coat isn't

a scratch coat isn't necessary if you can figure out thru innovation how to securely attach mud to drywall,,, once that's done, the same mud must cure to an acceptable finish OR should in our home or our client's homes.

most would prefer to apply a 1-coat system,,, the same folks would also prefer putting 5gal of wtr into 4gal bkts thereby lowering bucket costs,,, we just don't have the technology or materials for either yet.

1 pertinent suggestion would be for you to post this thread in the ' Vertical Overlays, Rocks & Waterfalls Forum ' forum,,, it may be more relevant to those who are directly concerned w/that application,,, perhaps you can post the results of your experimentation for us as you progress,,, best wishes !

Lindy A.'s picture
Lindy A.
Nathan Griffin is the most

Nathan Griffin is the most knowledgeable, skilled, contractor I know of when it comes to vertical applications. If you go to his Vertical Artisans website you will gain valuable insights and learn his successful how/to techniques. There are numerous "free videos" on it that you can watch as well that are very entailed and there is also a "forum" pertaining to vertical applications that is frequented by those that are "vertically focused." I think that once you review the content of his site you will have found answers to all your questions/concerns and will be on the road to getting the job done in a professional appealing and lasting manner. His resouceful knowledge has true value.
Lindy A.

Vertical Overlays forum? Is

Vertical Overlays forum?

Is that a different website?

Lindy A.'s picture
Lindy A.
On home page, where you see a

On home page, where you see a listing of all the DCF Forum categories, you will see the one titled "Vertical Overlays." Again, I strongly encourage you to visit the website of "Vertical Artisans" that I referred to above as well.
Lindy A.

I am a member on vertical

I am a member on vertical Artisans free forum, which is more focused on carving than overlays. But thanks for the suggestion.

Lindy A.'s picture
Lindy A.
Oh ... I thought Nathan

Oh ... I thought Nathan focused on both carving and every other type of Vertical concrete (including overlays).
Lindy A.

There are artists there that

There are artists there that do overlays, but I actually have not seen anything that Nathan has done that is an overlay? Maybe I missed something?

Anyway I did find the thread for vertical overlays here.

Lindy A.'s picture
Lindy A.
I did the entire outside of a

I did the entire outside of a building once using overlayment materials.
(1) first, sheeted the building in Styrofoam panels, attaching them with screws through a washer (where they were countersunk in a ways).
(2) then wrapped the entire building vertically over the all the Styrofoam with window screening, attaching with a hammer stapler, in order to deflect any movement out over the entire expanse of the Styrofoam walls. Also added a ledge, using molding about 40" up all the way around the building.
(3) next, using a hopper gun sprayed on a heavy coat of overlayment material (integrally colored the mix a medium gray), troweled it smooth to totally encapsulate the window screening and coated the ledge with it as well, allowed to dry
(4) mixed up more overlayment material, integrally coloring it to a brick red, applied it over a running bond brick pattern I created using grouting tape, spraying it on heavy, troweling it down, allowing to dry, pulled tape ... outcome was a red brick pattern with a dark gray grout, that carried over the ledge I had made.
(5) above my faux brick with ledge, I shot a light gray overlayment with one hopper gun, splattering on a darker gray with another hopper gun, troweling them together sort of swirling them to get a two tone marble like effect.
(6) then sealed all the vertical exterior wall surfaces at one time.
This has been about 20 years ago ... has held up well, still looks good.
Can apply overlayment materials over various composites ... I have never done so over sheetrock since I don't believe it has much integrity to it (as compared to hardybacker, plywood, masonite, etc.) Only in the case of applying overlayment materials over styrofoam would it need reinforcing such as I did. Personally I think scratch coats even out vertical or flat work moreso for greater substrate uniformity than not doing a scratch coat at all.

Overlay Recipe?

Hi guys,


Awesome website and fantastic knowledge out there.

I am based in New Zealand and I am looking to g down the line of doing vertical overlays but need a mix design.  I have looked at all of the pre bagged mixes but it would cost a fortune to ship it to New Zealand.  I am hoping that someone may have a mix design that I can make up here myself.  I already do a lot of overlays ojn the ground but it looks as though there are some additives used to get it to sit up on the walls and not slump and also retardeents maybe to make it set slower?


Any help you could give me would be great.