Rethinking Window Flashing

(ONLINE, 10/23/15) Matthew Amann (online, 10/26/15): One of the major problems with any window flashing system is housewrap. I have seen too many times that non-backprimed cedar and other tannin-rich wood siding “clog” the pores of the housewrap, causing moisture intrusion and condensation problems.

I have had great success staying out of trouble by not following anyone on the window flashing, using acrylic adhesive flexible flashing, using tar paper instead of housewrap, and applying all three layers of waterproofing starting at the housewrap. I have seen too many windows caulked and flashed to bare OSB! What sense does it make for the primary waterproofing layer to start at the rot box?

Harrison McCampbell responds: Thanks for your input. I still recommend, and stand by, using a 30-lb. felt and covering that with housewrap (ideally, DuPont’s Stucco Wrap or another “drainable” housewrap). This, of course, must be done in concert with a properly installed flashing system around doors and windows and along finish-floor levels.

Editors respond: As Matthew notes, tannins in some woods like cedar increase moisture intrusion, but not for the reason he describes. Tannins decrease the surface tension of water, allowing water to more easily slip through the pores in a housewrap. Surface tension is what keeps water droplets in bead form; as a droplet, it is too big a molecule string to get through the microscopic pores in housewrap materials. When the tannin concentration in water reduces the surface tension, it essentially destroys the housewrap’s effectiveness as a water barrier. For what it’s worth, soap has the same effect. Some stucco installers will add a detergent to their stucco mixes to improve workability, but this practice should be discouraged.

Q&A: Setting a Toilet over Tile

by Terry Love (Apr/05)

BobboMax1 (online, 10/21/15): I’m completely against cedar shims—they’re subject to permanent compression over time. Or, when someone heavy sits unevenly on the toilet, cedar shims can be crushed and the wax ring can be permanently deformed at the same time. The cross grain of cedar is pretty weak in compression. I might accept oak shims, but otherwise, plastic shims are better. As for the taper, I think that’s a “so what?” As long as you can get the tip under the edge of the base, the taper doesn’t matter. I carry 1/32-inch sheet plastic for really thin shimming. I do find plastic to be more difficult to trim, but doing good work is sometimes difficult.
Because wax rings can be permanently deformed by a rocking toilet, I like the idea of the Fluidmaster Wax-Free Gasket, although I just bought my first one and haven’t installed it yet. I trust Fluidmaster to be a good supplier.
As far as caulk, apparently code does require it, but I think the requirement and the reasons given are bogus. Supposedly, if the wax ring leaks, caulking will contain the leak, which is supposed to be more sanitary. To me, it just contains the leak until the floor rots out—I’d rather be notified by a leak before that happens. Some clients do prefer the neat look and better “cleanability” of caulk, so my compromise is the same as Terry’s: I caulk three-fourths of the perimeter. This is particularly functional when you have to shim at the front of the bowl. One way to address dry rot due to leaks is by caulking the flange to the flooring, which is generally waterproof. On a reset, I’ve been known to use a putty knife and the old wax ring to seal the flange to the flooring.

Gkeway (online 10/21/15): I seem to recall that Rex Caldwell prefers to level a toilet using pennies. Regardless, I think this demonstrates a clear need in the industry for better plastic shims. For as much as toilets cost these days, I should expect the toilet manufacturer to supply shims with its products.

Editors respond: There is a product out there that may fit the bill. The Tile Buddy ( is a square toilet flange that includes a 1/4-inch-thick polypropylene shim that slips over the toilet waste pipe and provides support for the flange bolts. Lauren Hunter covered this in Products (Mar/15), reporting: “Multiple Tile Buddys can be stacked to equal the depth of surrounding flooring, allowing the flange to sit on top of the Tile Buddy at a height even with the floor. The square design also improves ease of installation for surrounding backerboard, tile, or other flooring surfaces by eliminating the need to cut or nip around a rounded flange. For renovations, the Tile Buddy features pre-scored lines that allow installers to snap the shim in half and slide each half under the existing flange to bring it level with the new flooring.”