[farmerjohn1324]

The first story is block with stucco. The second story is wood framed with lath and stucco.

https://buymbs.com/p-118-mfm-window...jcsFgUm2600HfeA-sG1OVNJ9Km0bu4tgaAlZwEALw_wcB

 

[chandler48]

New construction windows and doors certainly need Tyvek wrap and window/door tape. The way you are describing it, the stucco exists and you are installing replacement windows. Fill us in on what you are doing, and post some pictures.

 

[Windows on Wash]

Stucco installs can be tricky. Lets see what you are seeing.

 

[farmerjohn1324]

New construction windows and doors certainly need Tyvek wrap and window/door tape. The way you are describing it, the stucco exists and you are installing replacement windows. Fill us in on what you are doing, and post some pictures.

Stucco installs can be tricky. Lets see what you are seeing.

The windows and doors are not on site yet. The stucco installer says he needs them in before he can work. Pretty sure he's doing lath on wood only.

 

[chandler48]

So this is new construction. House should be wrapped in WRB, before you install the windows/doors. Cut the Tyvek back 2" back from the bottom and sides of the window flange. Apply 6" tape onto the flange and the tyvek, including the 2" of bare osb. Now, the top Tyvek is cut flat onto the flange and taped down to form a flashing. Then your normal flashing is installed over the window, unless it is going to be vinyl siding.

Doors are installed over Tyvek wrapped into the opening.

 

[farmerjohn1324]

So this is new construction. House should be wrapped in WRB, before you install the windows/doors. Cut the Tyvek back 2" back from the bottom and sides of the window flange. Apply 6" tape onto the flange and the tyvek, including the 2" of bare osb. Now, the top Tyvek is cut flat onto the flange and taped down to form a flashing. Then your normal flashing is installed over the window, unless it is going to be vinyl siding.

Doors are installed over Tyvek wrapped into the opening.

Does the paper backing of the stucco lath taking the place of the Tyvek on the second story wood?

 

[chandler48]

Just plain paper, no. Is it considered a WRB (weather resistive barrier)? Ask the stucco guy. You will need a WRB to prevent water infiltration and to let the house breathe to the outside. I am not versed in stucco, so ask him what is normal.

 

[ClarenceBauer]

Paper backed Diamond metal lath is designed for exterior use.
For a second story building he should use 3.4 lb. per sq. yd. color code will be RED, Paper should comply with Federal Specification UU- B - 790 Grade paper.
Make sure your Stucco contractor installs the paper Lath as per ASTM standards
or your Stucco will CRACK.

 

[chandler48]

Does the paper backed lath suffice as a WRB ?? Curious.

 

[ClarenceBauer]

Does the paper backed lath suffice as a WRB ?? Curious.

The answer is yes.
UU-B-790a Building Paper, Vegetable Fiber, Kraft Waterproof & Fire Resistant.
My opinion it is not as good as 15# felt Paper as a lath backing reason being, is too many mistakes can be made when it is installed this type Lath.
Problems that occur on installation # 1 Joint laps are incorrect, # 2 When lath is cut to fit the space lath & paper are cut @ the same time causing a lap problem. # 3 If a mistake is made during installation it is very hard to see.
When the above mistakes are made the Stucco will crack & you will have water intrusion plus incorrect lap joints will cause water to go behind the barrier paper.

 

[Windows on Wash]

Closed corner drip caps too.

 

[chandler48]

I thought the cutting of the lath would make the membrane non continuous, so IMO Tyvek or equivalent would be a good idea for a WRB, and cracks in the lath membrane would be less of a problem.

 

[ClarenceBauer]

I thought the cutting of the lath would make the membrane non continuous, so IMO Tyvek or equivalent would be a good idea for a WRB, and cracks in the lath membrane would be less of a problem.

Non continuous backing is the problem when Lath is cut wrong.
You have to make two cuts, the paper is cut 2 inches larger than the lath.
When installed it must be paper over paper & lath over Lath, this is where the mistake is made on installation & it causes cracking.
I will agree that a water barrier should be installed first than inspected before lathing is started.

 

[carpdad]

This is just a general interest question.

Overlapping the lathe as such sounds like metal and paper layers are separated and the overlaps are paper to paper and metal to metal, like a finger joint? But since top layer (of the overlap) is metal anyway, can they be overlaped without the finger joint? That is, just overlap the top layer, paper and all, over the bottom layer?


Second is, for maybe easier install and the cost, tar paper is better? Tyvek's advantage would be it can breathe, but in this case, does the lathe's paper layer act like a vapor barrier anyway?

 

[ClarenceBauer]

This is just a general interest question.

Overlapping the lathe as such sounds like metal and paper layers are separated and the overlaps are paper to paper and metal to metal, like a finger joint? But since top layer (of the overlap) is metal anyway, can they be overlaped without the finger joint? That is, just overlap the top layer, paper and all, over the bottom layer?


Second is, for maybe easier install and the cost, tar paper is better? Tyvek's advantage would be it can breathe, but in this case, does the lathe's paper layer act like a vapor barrier anyway?

First question on over lapping.
If you don't lap paper over paper & metal lath over Metal lath you will create a bond breaker for that length of lath, vertical joints will act the same which will cause cracking along all seams that are lapped wrong.
The Lath paper will act just like the Felt paper or Tyvek.
Tyvek will have a much higher PREM rating. If Tyvek is selected you should use the quilted type for water drainage.
There is also some very good liquid applied water barrier on the market that when applied as per instructions work better than any of the paper type barriers & are self sealing when the lath fasteners are installed.