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RE: GSBN:Straube Plaster Report

I would ask Don Fugler if it is OK to distribute this report widely.  He
would likely prefer to have you download it from a CMHC website, thereby
quantifying and tracking the interest in SB (and supporting future work).
Don? What do you think?

John Straube
Civil Engineering Dept and School of Architecture
University of Waterloo
T: 519 888 4015 		F: 519 888 6197

-----Original Message-----
From:	the black range [mailto:blackrange@zianet.com]
Sent:	Sunday, December 03, 2000 10:25 AM
To:	GSBN@...
Subject:	GSBN:Straube Plaster Report

Rob Tom mentioned the John Straube Report on Plaster and Stucco.  The
Conclusions it reached are below.  I have the 17-page report in a PDF file
(I bet John does too) available via email.  Should I post it?  (It's a big
file...) - Catherine Wanek

Moisture Properties of Plaster and Stucco for Strawbale Buildings CMHC
John Straube 			PG. 17

6 Conclusions
Based on the test data, several conclusions can be drawn:
1. Cement : sand stuccos are relatively vapour impermeable, in fact a 40 mm
thick cement stucco will act as a vapour barrier.

2. The addition of lime has a dramatic effect on vapour permeance. The pure
lime samples are very vapour permeable.

3. Applying an oil paint to a moderately permeable 1:1:6 stucco will
provide a permeance of less than 60 metric perms (1 US perms) and thus meet
the code requirements of a vapour barrier.

4. Applying latex paint to a 1:1:6 stucco reduces the permeance to about
200 metric perms (3.5 US Perms).

5. There was no large differences in behaviour between quicklime and
hydrated lime, although they behaved differently during application.

6. Quality elastomerics appear to high vapour permeance and low water
absorption. The performance of these products after a year or two of
exposure should be investigated. The use of vapour permeable elastomerics
can be recommended based
on these tests.

7. Siloxane appears to have no effect on the vapour permeance of cement and
cement:lime stucco while almost eliminating absorption. The use of siloxane
can be recommended based on these tests.

8. Linseed oil is not a very effective water repellent and does not
restrict vapour permeance. Thicker layers, and more coats should be

9. Calcium stearate as a cement additive reduces the vapour permeance and
has little effect on water absorption. Its use is not recommended based on
these tests.