I am building a two story addition, the top story will be sided with 1×10 clear redwood and the bottom will be stucco. For a double-layer of protection, I have installed Tyvek over the sheathing on the entire addition, and am planning to add 30 lb. felt under the siding and then stucco paper under the stucco. First question, I am told that the stucco paper over the Tyvek is a bit overkill, but it shouldn’t hurt, should it? Second issue, where the siding will go, should I put furring strips over the Tyvek before I install the felt or just layer the felt directly over the Tyvek? I have back-primed the siding.
One more question…at the bottom of the stucco, I used a 18″ layer of bituthene. I overlapped it 4″ with Tyvek, then stucco paper will go all the way down. Sound correct?
Thanks for your imput!
Jack
Replies
I don't know if felt over the Tyvek is a good or bad idea. My concern would be that Tyvek is designed to breath and I don't know if the felt will impede this significantly or not.
If you do use furring strips, creating a rainscreen, I would definitely not use 30 lbs felt behind the siding. Part of the function of the air space is to allow back of the siding to dry. The felt will not allow this to happen. Also unless it is a very deep airspace chances are the felt will make contact with the Tyvek behind allowing moisture to bridge the gap.
For your rainscreen to work properly, the siding over the furring should be open on the back so it can dry to the cavity, so the felt goes right over the Tyvek before furring strips go on. Also, the cavity has to drain out the bottom. Unless you also set your stucco lath on furring, this could be hard to ensure.
You could have a weep screed above the stucco to drain the siding portion, then another beneath to drain the stucco portion.
Bill
Thanks for your thoughts. I will heed your suggestion and put the felt over the Tyvek, then furring strips and finally siding. I have stucco-molding which is at the bottom of the siding that the stucco gets troweled up to. I plan on caulking the Tyvek to the back edge of the stuccomold, and the felt will be a 1/2" higher so that any moisture that gets behind the felt will make it's way down and out - effectively a weep screed. Let me know if you see a problem with this approach.
Jack
Stucco, the real stuff, Two or three coat, wants an air gap. Traditionally, the felt would pull away from the cement. With full sheathing under the felt, this couldn't happen.
If you're using "chicken wire", you want the felt over the furring. If you're gonna use diamond mesh, you could put it under the furring.
I worry about how the Tyvek will react to the petrochemicals in felt.
Felt is not an air barrior since you never seal the edges.
At the top of the stucco, use a wide flange mould, cut the house wrap 6" above it, and slip a 1' wide piece under the top wrap and over the wide flange.
Shingling the drain plane over the moulding at the bottom is correct, but I still wouldn't use tar felt over Tyvek. I dunno, it just feels hinkey to me.
SamT
Should I not put the 15 lb. felt over the Tyvek where the siding goes?
Jack
I don't know. I would get ahold of Tyvek and see what they say about tarred felt in contact with their material.SamT
Good recommendation...I called Tyvek where the people were incredibly helpful. For my application, they absolutely recommend 15 lb felt over the Tyvek, then furring strips, then siding. thanks for your help. Jack
SamT
Stucco requires 2 layers of felt. The reason is that new felt bonds with the stucco and water may get behind the felt if the stucco pulls away from the wall sheathing. (apparently older felt would separate from the stucco and stay on the sheathing, before my time though). With 2 layers of felt they separate, the first layer stays next to the sheathing, preventing water from getting behind the felt. Felt is not moisture proof and will breath. I'm not sure what the tyvek gets you on the first floor that 2 layers of felt and stucco dont. Make sure you trim out around windows/doors for an extra 1 inch thick material as when your stucco is done it's an inch or better with topcoat. (I use 2 by stock for trim).
I understand that the use of Tyvek under the felt stucco paper is a bit redundant, but I've seen it done that way in my neighborhood (West Los Angeles), and since I am using the Tyvek under the siding, what am I to do with the left-over wrap? I am a diy'er and am unlikely to have a use for it in the near future...I hope.