1. Lennar Corporation 2nd Installation set of Sealed Stucco System on two residential 2 story homes Report 2 – 08/24/17 The Stucco Institute Contact: Robert Koning - Director 8301 Joliet Street Hudson, Florida All material Copyrighted 2017

2. Sealed Stucco System Test on Two Residential Homes – Lennar
On June 29th 2017, Lennar Homes began installation of the second set of Sealed Stucco System installations on two homes in the Lakeside Subdivision in Hudson, Florida.
The two homes were located at (Lot 14) Tensaw Drive and (Lot 11) Tensaw Drive respectively.
The purpose of the installation was to demonstrate the Sealed Stucco System and to document
its efficacy when compared to an unmodified ASTM C-926 and ASTM C /8, 3 coat stucco system.
Until recently (circa 2004) ASTM C-926 stucco provisions were regionally modified. Without these modifications, they have now been failing for several reasons related to ignoring those time proven necessary modifications for installation, accessories, attachments, coatings and sealants.
These issues are solved by the sealed stucco system. See articles at 11 14

3. Sealed Stucco System Test on Two Additional Residential Homes – Lennar
Previously, on November 28th 2016, Lennar installed the Sealed Stucco System on two homes in the Lakeside Subdivision in Hudson Florida (13937 and Lugano Court).
The purpose of this installation was to continue the demonstration of the Sealed Stucco System and documentation of its efficacy as a code approved stucco system in opposition to an unmodified ASTM C-926 and ASTM C /8, 3 coat stucco system.
The results of the previous installations (see Lennar Report #1 – 12/16/16) yielded a crack free and fault free installation.
Since installations of these Sealed Stucco Systems have been servicing the Florida market for well over a 1/2 century without failure,
these results were not only expected – they were intended.
These homes contained 40’ long x 10’ high walls, solidly sheathed with structural panels (OSB), then covered with standard “Tyvek”.
StructaLath was then directly applied (no bond breakers or intermediate plies were added) to the wall with standard pan head lath screws.
No control joints, or corner beads were used (corners were traditionally “rodded”).
A mid-wall transitional weep screed was used to transition the StructaLath/ block wall intersection. Its purpose was to provide a transition screed for the dissimilar bases and was not installed for drainage purposes.

4. Sealed Stucco System Test on Two Residential Homes – Lennar
Stucco was then tightly applied by hand using the 3 stroke application methodology, (troweled up, down, and up) to ensure all voids, gaps, air pockets or spaces of the lath were filled with stucco mix. All drainage cavities were intentionally eliminated.
GENERAL DISCUSSION
Lennar and other major builders have been subject to a rash of litigation claiming “defective” stucco installations applied circa 2005 forward.
Although the subject is rife with complexities and variables, the majority of the problems are related to the seemingly (although incorrect) code compliant installation methodologies applied by those who remain untrained in the proper design and application of Florida specific code compliant installations.
Since the beginning of metal lath use, traditional plasterers installed their stucco assemblies directly to lath that was applied over a layer of felt paper. “V” grooves were cut and “brush sealed” at all intersections of dissimilar materials to allow for proper sealant setting, tooling and bonding. A proper coating (painting) was then applied to the correct thickness.
These jobs were all done with flat un-galvanized lath, nailed tight to the wall (no furring) and have continued to perform flawlessly for over 70 years.
When the ASTM C-926 and 1063 eventually made their way into the code, regional plasterers knew it was a western developed standard and could not be applied as developed for Florida’s general environment.

5. Discussion
The standard was then, as today, developed for lath over open framing, (or non-structural sheathing) and finished with colored stucco, i.e., no paint. Accordingly, water that enters the system through cracks, will migrate down the back of the lath and exhaust out a “weep” screed at the bottom of the wall by way of a “drainage plane”.
Initially, Florida plasterers knew that this methodology would never work in their environment since all water migrating from the surface through to the back of the stucco assembly would carry migrating salts. The result would be rusting of the lath and metal accessories.
Since the aforementioned ASTM standards are “International”, they need to be selectively modified for compliance in selective regions.
Original ASTM language such as “the decision to use them…” was included to allow such modifications. Later, the provisions were collectively gathered and singularly stated as “unless otherwise specified”.
These modifiers have always allowed time tested and proven regional installation methodologies to continue.
The basis of the Sealed Stucco System is simply a recommitment to those proven details, provisions, methodologies and traditions.
To continue historical installation methodologies in the building envelope science, the painting contractor then “rolled” two coats of the specified coating to its required mil thickness.

6. Discussion
Sealants (as opposed to “beauty beads”) were applied and tooled in place.
The sealants, applied into the “”V” grooves provided by the plasterer, along with the required coatings, melded into a outer “skin” that was not only waterproof, but bridged further cracking and stabilized the wall covering system.
Recent coating inefficiency (or more correctly, “deficiency”) is the prime source of the current stucco problems.
The Sealed Stucco System addresses and corrects this oversite with training and mandatory coating/ sealant requirements.
Aggravating the situation is the fact that we now use OSB as a substrate whereby plywood or angular wood sheathing planks were the sub-stucco material of our predecessors.
Although OSB and Plywood fall into the “Vapor Semi-Permeable” (materials with a permeance of 10 perms or less and greater than 1.0 perm), OSB has some characteristics that are not conducive to high moisture conditions if found trapped behind a stucco assembly.
First, consider a stucco assembly in Florida’s average annual environment; 88.5o Avg. High – 70.7o Avg. Low with Annual Relative Humidity from 88% Sundown – 59% Sunrise.
Next, consider a stucco system that has a drain plane that allows for the introduction of moisture laden air behind the assemblage. Coupled with a deficient face barrier (exterior coating) allowing for the migration of vapor through the stucco and around the accessories, the problem is exacerbated.

7. Discussion
Given such a system, the vapor conditions on the inward side (behind) the stucco will mirror those on the outboard (atmospheric) side of the assembly.
This collective high humidity will remain after sundown whereby radiant heat loss and/or sub-wall cooling, will cause the trapped vapor to condense at ≈ 84.5o.
The back side of the metal lath and metal accessories will be the first (and best) condensing surface. This chronic condition will lead to rusting of the lath, expansion of the metal and bulging (tented) stucco ruptures in the wall region.
Plywood has somewhat more forgiving properties for passage of the moisture.
In the report,
“Moisture performance properties of exterior sheathing products made of spruce plywood or OSB”(Tuomo Ojanen & Jarkko Ahonen, 2005), some important properties of OSB were noted:
Water vapour permeability
The vapour permeability of both OSB and plywood were in a relatively low level under dry conditions, but the level increased significantly after exposure to certain relative humidity levels. There was a significant difference between the products in this respect. The vapour permeability level of plywood was under 80 / 58 % RH condition measurements from 5 to 11 times higher than those measured under dry cup

8. Discussion
conditions for the same product. With OSB these values were only about times higher than under dry cup conditions. When the relative humidity test conditions were 97 %/ 72 % RH, the vapour permeability of OSB had increased to be about 4 to 9 times higher than in the dry cup tests, while the plywood vapour permeability level was 12 to 20 times higher, depending on the product. The back side of the metal lath and metal accessories will be the first (and best) condensing surface. This chronic condition will lead to rusting of the lath, expansion of the metal and bulging (tented) stucco ruptures in the wall region.
Plywood has more ability to increase its permeability (and therefore pass) higher levels of relative humidity to the interior under higher humidity levels. OSB is simply a better vapor barrier.
Additionally, the study examined the capillary capabilities of OSB:
Capillary water absorption
The final moisture content level of these four OSB products was about 2.5 times higher than that of plywood products.
Lastly (and of most importance), the effect of moisture and dimensional stability was examined:

9. Discussion
Dimensional Stability The dimensional stability of the product has an effect on the air and moisture tightness, thermal performance and even on the strength of the structure. High swelling of the material could be detected mainly in the board thickness. The relative dimensional change on the longitudinal direction was significantly lower than that of the thickness. The relative change of OSB board thickness under capillary contact was in the range of % and with plywood it was from 3 to 6 %. Most of the swelling of plywood boards took place in the hygroscopic area, but about half of the swelling of the OSB boards took place between 87 % RH and the capillary saturation conditions.
Change in the thickness of OSB board to an attached brittle stucco system will induce cracking, will induce water, which will rust lath, which will induce more cracking, etc... The dog chases its proverbial tail.
I told you all that to tell you this…..
In Florida, If you do NOT keep the water and vapor blocked at the face of the stucco system (face barrier system) – you will allow bulk water and vapor to migrate through and behind the stucco with devastating results. We have known this since we began stuccoing!!
Now you have arrived at the reason, purpose and need for the (old school) Sealed Stucco System.

10. The Sealed Stucco System Requirements
Installed by trained personnel
This need not be the stucco contractor. It can be the builder, superintendent, stucco contractor or other. What’s required is the certifier be trained to ensure (certify) that the components (regular materials) are assembled and applied to the required Sealed Stucco System Requirements.
Applied directly over the house wrap
No need for a bond breaker of other separation materials. Stucco installed over an approved house wrap seals and hydrates better than those over felt.
No need for troublesome accessories
No need for control (panel) joints. Most regional experts have always eliminated control joints from their stucco assemblies. If you want to use them for aesthetics, you may, just follow our installation guidelines.
No need for casing separation at windows, just follow the required “V” groove and sealant requirements
Windows are corner sealed to eliminate future joint leakage
No need for 7/8” – 3 coat application
The system required a full 5/8” thickness installed monolithically using traditional “Double-Back” methodology or you can scratch and finish the application if you wish
Highest pull-off resistance, (220 psf) easiest installation, proven over 40 years of trouble free service
The sealed Stucco System returns stucco to the art it was by involving all trades to intermesh the final product into a face barrier system.
Fully Code Compliant
See code compliance documents on or

11. Exemplary Photos of Installation

12. Lot 14 House Wrap Installed
Casing Beads or Weep Screeds installed as upper wall terminations at roof line. Casings or Weeps used as a screed stop only, this is a Face Barrier Systems so they are not part of a “drain-plane” system.

13. Lot 14
Mid-Wall transition Sub-Flashing. Minimum 6” wide Bituthene strip under Weather Resistive Barrier (WRB)
Mid-Wall transition Sub-Flashing. Minimum 6” wide Bituthene strip under Weather Resistive Barrier (WRB)

14. Lot 14
Application of Mid-Wall transition accessory. Used for screed and transition purposes on a face barrier system – not installed as a “weep” screed.
Rolling out and cutting of Application of StructaLath.

15. Lot 14 Rolling out and cutting of Application of StructaLath.

16. Lot 14 Application of StructaLath.
Application of StructaLath. Note lath lapped over CMU and stub nailed – no screed or casing needed.

17. Application of StructaLath.

18. Lath – All Houses
Sealing around penetrations. Note incorrect dryer vent type for stucco application.
Sealing around chase – ready for stucco

19. Lot 14
Attaching lath with screws
All lath installed, ready for stucco

20. Stucco Mix
Mixer was 9 CF. Cement Representative had instructed the crew to use 3 bags per mixer load (3:1) for all scratch and brown coats and 4 bags to mixer load (2.25:1) for finish coat. Both ratios being too rich.
We reduced the cement to 2 bags per mixer load (4.5:1) ratio for all scratch and brown coats and 3 bags per mixer load (3:1) ratio for the finish dash coat with dash-brush. Stucco contractors have been using way too much cement in their applications. Note: Sand box (shown) not needed, fill mixer to top of mixing paddles for 9 CF

21. Stucco Application
No Slickers allowed for any application. Cement Plaster (Mud) applied by hand using the “up-down-up” method. Mud pressed tightly (sealed) to WRB in order to eliminate all gaps, voids or crevice's.
No Slickers allowed for any application. Cement Plaster (Mud) applied by hand using the “up-down-up” method. Mud pressed tightly (sealed) to WRB in order to eliminate all gaps, voids or crevice's.

22. Stucco Application
Author showing crew how to “prep” a corner bead flange prior to application of stucco.
Author showing crew how to “prep” a corner bead flange prior to application of stucco. Second side. Note: These beads are not allowed over the frame wall – all upper outside corners were traditionally rodded to ensure a water tight corner.

23. Stucco Application
Second Coat after first coat began to set. Applied, rodded and then densified.
Densification. A critical step.

24. Stucco Application
Densification.
Application of the dash finish coat.

25. Stucco Application
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.

26. Stucco Application
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.

27. Stucco Application
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.

28. Stucco Application
Cutting “V” Groove – Followed by Brushing to seal channel for sealant tooling.
Stuccoed Wall with finish.

29. Stucco Application Stucco Application with Finish.

30. Stucco Application
Stucco Application with Finish cured ready for paint 10 days later. No wet curing, no cracks, no faults, no voids, application ≈ 5/8 to 3/4”.
Stucco Application with Finish cured ready for paint 10 days later. No wet curing, no cracks, no faults, no voids, application ≈ 5/8 to 3/4”.

31. Lot 14
Sealed and Coated to ≥ 12 mils – All upper window corners sealed.
Sealed and Coated to ≥ 12 mils.

32. Lot 14
Sealed and Coated to ≥ 12 mils.
Sealed and Coated to ≥ 12 mils.

33. Lot 14 Sealed and Coated to ≥ 12 mils – ALL Window Corners Sealed.

34. Lot 11
Completed as Lot 14
Completed as Lot 14

35. Lot 11

36. Lot 11

37. Lot 11

38. Lot 11

39. www.myfloridacode.org Code Discussion Forum SEALED STUCCO SYSTEM
Videos of the stucco applications and related articles are posted at
For more information on the standards and installation practices, refer to the Sealed Stucco System at:
The sealed stucco system is simply the traditional stucco application process used in Florida’s type climate for over 40 years with some modern modifications and products.
The system has been laboratory tested and approved.
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