[GSBN] Exterior plaster sealer

[RT]

On Fri, 21 Jan 2011 13:00:02 -0500, <gsbn-request at greenbuilder.com> wrote:

> Date: Fri, 21 Jan 2011 06:51:14 -0800
> From: John Swearingen
> Subject: Exterior plaster sealer?

> I'm familiar with DdB's house, one of my favorite sights along the  
> coast, and I can tell you that wood will not bend enough to clad this  
> house!  I've long been a fan of siloxanes, [snip]

> John "Bend it Like deBoer"  Swearingen

(full text of the Skillful Meany's mind-bending message and originating  
thread may be found at:

         http://greenbuilder.com/pipermail/gsbn/2011q1/001222.html )

I'm a fan of the building geometry method (ie ventilated rainscreen  
cladding systems ... enclosed porches,lattice screens, berms with  
coniferous plantings etc. on windward elevations) vs the painted-on  
chemical stew method (ie latexes, oils, waxes, silanes/siloxanes etc.) of  
keeping wind-driven rain off of moisture-susceptible wall materials.

Especially when trying to keep plaster (and the materials behind the  
plaster) dry ... simply because plasters can develop cracks (from both  
structural stresses (ie seismic or wind loading) and those induced by  
temperature & shrinkage stresses or just plain poor plastering practises)  
long after the application of the sealer which is typically applied  
shortly after the building's completion.

(If you can find the charts that show the volume of rain that can pass  
through various crack widths for various wind velocities, you'll  
appreciate the "minimise potential crack exposure" approach which applies  
to cladding as well as plumbers.)

As for the "inability-to-bend-to accommodate curved surfaces" issue which  
the Meany mentions, one notes that when faced with the prospect of  
cladding difficult compound-curved shapes in difficult climates (ie onion  
domes in the former USSR or ornate Victorian and Queen Anne style homes on  
the North American north-east Atlantic coast ) rather than try to  
steam-bend large pieces of wood,  small shingles (either diamond-shaped  
sheet metal with fold-locked seams on the four edges (best) or  
multi-layered wood shakes or shingles ("good 'nuff")) were the  
traditional, time-proven effective methods of choice.


For a plastered SB wall where there aren't a whole lot of places one can  
whack in a nail to hold up furring strips and nailers, the rainscreen  
cladding system is probably best conceived of as a pre-fabricated (or  
pre-cast or tilt-up) panel system, the individual panels clipped to the  
building with points of attachment at sill, ribbon joist, door & window  
jamb/head/sill and top plate locations.

ie instead of nailing furring strips to the building and then nailing  
cladding pieces to the furring strips, integrate the furring strips and  
cladding to create self-stiffenned panels  or ribbed/waffle shapes if  
pre-cast or tilt-up panels).

This approach affords one the opportunity to make the cladding panels in  
an easier-to-work on horizontal orientation, protected from the elements  
if desired, without any exposed mechanical fasteners which can lead to  
localised deterioration of the cladding at the fastener penetration  
points, not to mention deterioration/failure of the fasteners themselves  
... all of which is amenable to doing a better job.


-- 
=== * ===
Rob Tom
Kanata, Ontario, Canada
< A r c h i L o g i c  at  Y a h o o  dot  c a >
manually winnow the chaff from my edress if you hit "reply"
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