Detailing WRB at electrical conduit exits, stucco patch job
severaltypesofnerd
| Posted in General Questions on
Where can I find a guide to doing a great job at making sure an electrical penetration will never contribute to a leak or rot?
This corner has a 1/2 copper pipe, place for new outlet, place for motion sensor light, and cat5 cable for a security camera and mount for a hose reel. How best to detail the WRB penetrations?
Is there a good guide somewhere? The corner will be stuccoed with two layers of Grade D, then a rain screen, then wire, using conventional stucco nails, and one vertical expansion joint.
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Replies
Bryce,
You might want to detail these penetrations with Roflex gaskets. To see photos of penetrations sealed with roflex gaskets, click through the photo gallery accompanying this article: "Urban Rustic: Air Sealing the Exterior Sheathing."
For more information on Roflex gaskets, visit the 475 High-Performance Building Products web site.
And by the way, I hope you live somewhere very warm, where temperatures rarely or never drop below freezing. If you don't, you should swap out that sillcock for a frostproof sillcock.
Hmm, I don't see a product in the Roloflex catalog for 1/2 pipe.
I've used similar "Quickflash" products in the past. I'm not convinced the rubber on those will last the distance... all the old rubber I've seen from 20+ years is dried out and hard.
This house was built 1938. Climate is non-freezing, San Francisco Bay Area fog zone. Quakes are the big risk, and will crack stucco and disturb caulked joints. I've seen a lot of what works over 70+ years, and a lot of what did not.
I'll hide some of the penetrations under the very small eve, as natural protection always seems more robust for the long term compared to caulk/glue/rubber.
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For today I have to make one of the conduit penetrations work, with no special flashing, just common building materials. In that case, what would you suggest?
The rubber on Quickflash should last forever behind the stucco. it's the sun that does most of the damage to exposed rubber products. And, the rubber is far more tolerant of movement than caulk or tape.
"Making sure a penetration will never leak" isn't really compatible with "for today I have to make one of the penetrations work with no special flashing." If you want a lifetime solution, you need special treatments.
That said, you can hang a strip of paper with a half circle cutout at the top edge around the bottom half of the conduit, and tape the conduit to the top of the paper and run the tape 6" each way to seal the top edge of the paper. Then, cut a slot in the next piece of paper and fit it over the conduit so that it overlaps a few inches over the first layer. Tape that piece around the conduit too. A bit time consuming but it works.
I see a QuickFlash flashing sitting on the ground in the photo. These are one of the best solutions for sealing penetrations in the WRB. In addition to the one you've got for the electric box, they make them for pretty much any other sort of penetration. Vycor Plus and Vycor Pro are compatible with grade D paper, but I find the Pro version sticks better for taping the flange of the QuickFlash.
I would move the sillcock and electric conduit far enough apart that you can use individual Quickflash panels properly. If you need to have several wires coming out of the same spot, you can install a piece of PVC conduit that is large enough for all of them and seal the conduit with Quickflash. Then pull your cables through the conduit and seal around them. For electric outlets, I prefer to seal around the conduit, install the stucco, and then fasten the electric box to the surface of the stucco, trimming the conduit to just penetrate the box. For the hose reel you can stick a layer of Vycor to the Grade D paper right where the fasteners are going to penetrate. The Vycor will seal around the fasteners a bit better than the paper. Or if you are using fatter screws, fill the holes with caulk before installing the screws.
Also, you don't need any vertical control joints on that narrow wall. The corners act as your control joints. Fold a strip of self adhesive flashing tape around the inside and outside corners for extra water protection because corner beads always leak.
Finally, make sure that all of your flashing and sealing is done at the level of the first layer of paper. The second layer is just a slip sheet to keep the stucco from sticking to the first layer. Water should drain between the layers. If you are using a scrim-covered rain screen, you don't need the second layer of paper.
Local code requires the 2nd layer of paper, as it does not recognize the scrim rain screen. Thank you for the tip that the 1st layer is the air barrier.
For the hose reel I was considering a threaded stud which would sit proud of the stucco in just the right spot. Then I can caulk and seal without the need to drill later.
Unfortunately I have three penetrations for wires, because they're different spots, and because one is low voltage and can't share conduit with the line voltage.
Is there such a thing as a corner bead control joint?
Corner beads act as control joints. The whole point of a control joint is to relieve the stress of the stucco curing, building movement, etc. This happens naturally around a corner, where the stucco inevitably cracks as the corner moves. If you use a corner bead, the stucco simply cracks at the corner bead or the corner bead moves in and out with the building movement. The ASTM standards require control joints to separate the stucco into 144 sf panels. Windows, doors, corners and other natural stops in the system count as control joints. So, a small panel like the one you showed does not require any control joints - just the corner details. I like to use corner bead, but Cornerite also works, or just wrapping the lath one full stud around the corner. They all relieve the stresses, but the cracks that happen with wrapped mesh are a bit uglier than the straight ones on corner beads.
The hanger bolts you show are a good way to go with the hose reel. You can seal them at the WRB pretty well. For the wires, I would still install PVC conduit and seal that to the WRB, then pull the wires after the stucco is finished.
Bryce,
I find the most effective way to deal with penetrations, be they conduit, duct-terminations, outlets, or things like hose-reels, is to provide a solid mounting block of either plastic, fibre-cement, or PT wood that is slightly proud of the wall finish. Some like those for light fixtures, can be bought pre-made. The mounts are much easier to flash than a hole.
An example: http://www.sturdimount.com