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CCW 705 Waterproofing on this Parapet Cap is Best Practice.

by • June 17, 2014 • Exteriors - Siding, Stucco, Brick, Stone, Wood, Metal, Housewrap & WaterproofingComments (2)8697

Stucco Parapet Caps – Best Practice

If you missed my post last week on the Massive Stucco Failure I’d highly recommend reading that post before going further here…

In general, you are always better to cap your parapet walls with metal rather than Stucco’ing over them.  But, what if your client/architect doesn’t want that look?  I’m building a Spanish Colonial Style house on Lake Travis right now and my clients/Architect on the project really wants the traditional look even though I’ve got some flat roofs and stucco.  Here’s an elevation from the Architect.  It’s tough to see in this drawing, but the roof over the front door is a flat roof with a stucco parapet cap.

Spanish Colonial Styled Custom Home by Architect Rick O'Donnell

Spanish Colonial Styled Custom Home by Architect Rick O’Donnell

In light of those massive failures I showed last week, I thought I’d show you how to avoid those issues and do this Stucco Parapet Cap the Best Practice way!

First, have your carpenters frame the parapet cap with slope to the inside so any standing water will drain in the proper direction.  You don’t want a true flat cap.  Next, I have my frame carpenters wrap the house in Tyvek Commercial D and fasten it with a Stinger Cap Stapler.  This is my go-to house wrap when I’m installing stucco, or just about any facade really.  This crinkly version of Tyvek Commercial wrap is both jobsite tough AND will provide a nice drainage plan behind the stucco.  Here’s a great video I made a few years ago to show how well the crinkles move water out of a leaky assembly.

 

Tyvek Commercial D installed after framing.

Tyvek Commercial D installed after framing.

Next, I’ll bring in the roofer to do the underlayment for the pitched roofs.  My go-to roof underlayment is Carlisle’s WIP 300HT for any roof I build here in Texas.  I also have them install the roof membrane on flat roofs during this visit.  I use Carlisle’s white TPO which is perfect for our hot climate.  Always remember to work from the BOTTOM TO THE TOP when doing waterproofing.  You really want that Flat Roof membrane down before doing the parapet cap waterproofing.

We the cap waterproofing by stripping off any Tyvek to get to a bare substrate.

We start the cap waterproofing by stripping off any Tyvek to get to a bare substrate.

Anytime we have a 90 degree turn in a cap I want a good membrane at these critical junctions.  Tyvek Flexwrap is what I use.

Anytime we have a 90 degree turn in a cap I want a good membrane at these critical junctions. Tyvek Flexwrap is what I use.

Tyvek Flexwrap on corners first. THEN sheet membrane

Tyvek Flexwrap on corners first. THEN sheet membrane

I like to get to bare plywood before doing any peel & stick membrane as I know I’ll get good adhesion to the plywood.  I recommend using 3M High Strength 90 spray adhesive before adhering the Tyvek Flexwrap in the corners to ensure a good sticky bond to the plywood.  Lastly, we do the real waterproofing.  The Flexwrap is what I use to make sill flashing pans for  my windows and it’s a very versatile product that works great in this application.   The sheet membrane we apply next doesn’t stretch so Flexwrap in the corners makes this tough spot easy to detail.

3M High Strength 90 makes a great primer for any sticky flashing.

3M High Strength 90 makes a great primer for any sticky flashing.

OK, Now it’s time for the bulk of the cap flashing.  I like Carlisle’s CCW 705 peel & stick membrane.  This is a 40mil thick product and is very similar to an ice/water shield product you may have seen used on roof edges & valley’s up North to prevent leaks from ice damming.  It is a rubberized asphaltic product that has good self-healing properties around nail penetrations.  You really want this thick membrane under the stucco cap because water WILL get through the stucco cap someday.  There are a few other manufacturers of this type of 40mil product but you might need to hunt around to find it as it’s not typically stocked at the lumberyards.  I buy it from a Commercial Waterproofing Supply house in Austin called All-Tex supply.  You might also find a similar product at a roof supply house.  You could use WIP 300HT also.  But, whatever product you pick you want to ensure it wraps over the entire cap in one piece and hangs down 4-6″ for a good shingle effect.

With

We are using 36" wide rolls of CCW 705 and it's only practical to run them in about 6' lengths to ensure wrinkle free application.

We are using 36″ wide rolls of CCW 705 and it’s only practical to run them in about 6′ lengths to ensure wrinkle free application.

One of the reasons I like CCW 705 is that I can buy it in various roll sizes.  They stock it in 12″, 18″, 24″, 36″, and 48″ rolls at my supply house.  Sam my carpenter is running roughly six foot lengths so we can ensure a smooth wrinkle free (ish) install.  We always overlap the sheets by 6-8″, and if you’re concerned about adhesion you can spray the overlaps with High Strength 90 adhesive primer.

Overlap by at least 6" on the straight runs

Overlap by at least 6″ on the straight runs

_MG_9955

It's critical to use Flexwrap in the corners because of the cuts needed to the straight membrane.

It’s critical to use Flexwrap in the corners because of the cuts needed to the straight membrane.

_MG_9959 _MG_9960Now you can see why we really want the Tyvek Commercial D house wrap on first before waterproofing the caps.

Where the cap meets a wall we again want to run Tyvek Flexwrap.  Sam is using High Strength 90 to prime first.

Where the cap meets a wall we again want to run Tyvek Flexwrap. Sam is using High Strength 90 to prime first.

Flexwrap first, then flap the Tyvek back over.  This cap is done!

Flexwrap first, then flap the Tyvek back over. This cap is done!

There you go, that’s Best Practice for Stucco’d Parapet Caps.

Completed Cap is now waterproof and ready for the stucco crew.

Completed Cap is now waterproof and ready for the stucco crew.

_MG_2688 IMG_2700

This took some work and some dollars in product, but I’ll sleep well at night knowing these caps won’t end up looking like this someday!

 

Parapets walls were leaky & super rotted on this 10 year old restaurant I saw being remodeled.

Parapets walls were leaky & super rotted on this 10 year old restaurant I saw being remodeled.

 I’d love to hear your comments about this installation, and let me know how easy/hard it is to comment on my new blog below.  If you are getting to this post from another source I’d love for you to check out my archives at www.MattRisinger.com

Best,

Matt Risinger
Risinger Homes in Austin, TX

Risinger Homes is a custom builder and whole house remodeling contractor that specializes in Architect driven and fine craftsmanship work. We utilize an in-house carpentry staff and the latest building science research to build dramatically more efficient, healthy and durable homes.
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  • Andri

    Hi Matt. This is a great post to a difficult detail. I was curious to
    see how you guys did the actual stucco part. Especially how the lath was
    attached. This always seems like a crucial part to this detail since
    you potentially have to make wholes into the waterproofing in order to
    attach the lath with nails or staples.
    Regards,
    Andri

    • http://www.mattrisinger.com Matt Risinger

      Andri, Thanks for commenting. The stucco was applied traditionally (three coat system) with stapled lath. We went lightly on the staples on this install since it’s basically horizontal not vertical. Best, Matt