Parapet detail: Santa Fe building, desert southwest

[Cole Greenberg]

It seems that nearly everyone in Arizona is finishing parapet walls on "Santa Fe" type buildings using W.R. Grace's Bituthene product, although Grace specifically says do not use it on parapets in the desert southwest. OK . . . but if not Bituthene, what? And in what detail?

[NW Architect]

They probably say that because of the heat factor - Bithuthene is designed as a below grade waterproofing. If one really wants to use a peel-and-stick, then Grace Vycor Ultra, their high temperature formulation, is a choice. Some other manufacturers have high temp formulas.

Its also worth avoiding poking holes in the stuff. I assume the parapets are faux-adobe made up of stucco with bullnose detailing. I've done such parapets. Make sure the top of framing slopes towards the inside.Run whole sheets of lath over the top and fasten only on the vertical faces. Tie on the bullnose corner accessories. I've also been known to work a drainable horizontal joint onto the walls as close to the top as possible and coat the top of the stucco parapet with an elastomeric coating

[Toolwhore]

Cole;

That is a very good question. Grace makes alot of products that look similar, but are made up of different compounds and used in different applications. I've been researching this subject lately as I have a project like that coming up soon (Prescott area) and have never worked on one.

NW Architect;

Great info. I've studied the Grace website and still wasn't quite sure of a correct method. Thanks, very helpful.

[Dick Seibert]

Cole:

Good question, I've never understood W.R. Grace's product designations, and their representatives have never given me a good explanation as to why some are called Bituthene, Vycor, I&W Shield Etc. They finally do seem to be sorting things out, my first reaction would have been to say Vycor, but after reading the attachment below I would say Proprufe, which I've never heard of before. I would give their reps a call.

This is a good question because I've worked on a lot of old buildings from the 20s and earlier and those parapets are always rotted out, I've opened up those building to find nothing holding the buildings up but stucco and plaster, with nothing but powdered sawdust inside the rotted walls, all coming from leakage in the tops of the parapet walls. I understand the problem though, metal caps look fugly up there.

Another possibility is to go away form Grace to Fortifiber and install their Fortiflash.

[Bill Robinson]

A link to the WR Grace website, well I guess they dropper the WR so call it Grace.
Contractor's Guide - Windows, Doors and Detail Areas**NEW**

The key is to protect the self-adhesive from the sun--UV, slope the top inward and make sure the peel and stick is rated for horizontal applications.

I have attached the Grace detail you will find in the Contractor's Guide.

The final profile may differ but it is easy enough to make that happen.
As the NW dude says, do not put fasteners through the horizontal portion of the parapet. And there should be no true horizontal surfaces, slope them.

Bill R

[AZ Contractor]

They probably say that because of the heat factor - Bithuthene is designed as a below grade waterproofing. If one really wants to use a peel-and-stick, then Grace Vycor Ultra, their high temperature formulation, is a choice. Some other manufacturers have high temp formulas.

Its also worth avoiding poking holes in the stuff. I assume the parapets are faux-adobe made up of stucco with bullnose detailing. I've done such parapets. Make sure the top of framing slopes towards the inside.Run whole sheets of lath over the top and fasten only on the vertical faces. Tie on the bullnose corner accessories. I've also been known to work a drainable horizontal joint onto the walls as close to the top as possible and coat the top of the stucco parapet with an elastomeric coating

This is a very good explanation of what to do. Let me reiterate the point of not poking and holes in the horizontal part of the parapet. Its very important not to. Wrap everything around the front and back and use your staples on the front and back, only.