[GSBN] Drainage within a plaster system
Ian Redfern
ian at adobesouth.co.nz
Thu Jul 11 00:56:42 UTC 2013
Good afternoon John, Sven and All,
I like the concept of a thin drainage plane behind a rain screen which this
product will provide
HOWEVER secudrain is designed for horizontal loading where the product
resists crushing forces yet maintains in plane drainage e.g. Interlayers of
roads or landfills.
The apparent confusion is the pull apart strength (tensile strength) along
and across the sheet, not the tear off or SHEAR effect of vertical loads
where the rain screen plaster coats hang onto the outer skin of the cloth -
as John and found this stuff will tear apart !
So
My suggestion is to pin this over the (structural) scratch coat that is
direct plastered onto the straw, then overlay this with cintoflex D and lay
up the two or three coat lime plaster rain screen and finish this off with a
lime wash
The rain screen will be supported by the cintoflex (refer Bruce Kings book
for loadings and fixing tests) along the soffit line, and will need
additional fastening along the bottom plate above the J flashing. The
cintoflex will probably need some "anti billowing" fixings of say roberto
pins into the bales at up to 400 centers across the face of the wall
ian
www.adobesouth.co.nz Ian Redfern
Adobe South
A: 5 Lancewood Rise, Onerahi, Whangarei
P: 09 436 4040 M: 027 490 2324
E: ian at adobesouth.co.nz
From: John Swearingen <jswearingen at skillful-means.com>
Reply-To: Global Straw Building Network <GSBN at sustainablesources.com>
Date: Thursday, July 11, 2013 9:23 AM
To: Global Straw Building Network <GSBN at sustainablesources.com>
Subject: Re: [GSBN] Drainage within a plaster system
Sven...are you confusing "machine direction"? Doesn't it refer to tension
in the plane of the material. The sandwich materials like this that I've
seen can all be pulled apart by hand (we do it regularly), and that doesn't
seem strong enough for a major seismic event...
John "Cross Machine" Swearingen
On Wed, Jul 10, 2013 at 2:05 PM, Sarah Johnston <sarahjohnston at ihug.co.nz>
wrote:
> Thank you all for your thoughts...
>
> The plaster keys into the geotextile and the geotextile is well bonded to the
> mat. The specs say that the tensile strength (Machine Direction) is 7.5 KN/M
> for the mat with the geotextile bonded to both sides. I do not know what this
> number equates to in potential thickness of plaster hanging on it.... Any
> thoughts anyone??
>
> The secuDrain
> http://www.cirtex.co.nz/files/file/375/Std+Secudrain+131+C+WD+401+131+C%2C+Rev
> +5_en.pdf does seem like it should be better and the specs suggest the
> tensile strength is twice as good as the duraflow. The reason I have not been
> considering the secudrain over the duraflow is that the samples I have do not
> seem to reflect the data on the website. The duraflow was far more difficult
> to pull apart.. I guess it all comes back to trying them both on a wall, then
> test them.
>
> If we have living green walls like John suggests... Would that make us
> 'greenies'?
>
> Sven
>
> On 11/07/2013, at 2:47 AM, John Swearingen wrote:
>
>> The drainage mat is very thin, and I'm not understanding how you plan to
>> "embed" the mat to the base coat, and then bond the exterior plaster to the
>> geotextile, both securely enough to keep the plaster layer from falling off
>> in a good shake? BTW, I would consider using their "SecuDrain" rather than
>> Duraflow especially if you can get it with geotextile on one side only.
>>
>>
>> Have you thought of wrapping the building in something like DuraGreen? Never
>> mind the plaster, grow plants.
>>
>> John
>>
>>
>> On Wed, Jul 10, 2013 at 2:33 AM, Sarah Johnston <sarahjohnston at ihug.co.nz>
>> wrote:
>>> My intention would be to apply a 30mm clay/sand/straw plaster with this
>>> product embedded into/ onto the top of the plaster. Or 20mm of lime/cement/
>>> sand/ fibre plaster in place of the clay. This would be the typical
>>> structural plaster and the thin plaster over the drainage mat would be to
>>> visually hide the mat and stop the wind from driving rain through the mat,
>>> thus adding to the typical plaster rather than weakening the system.
>>>
>>> I am hoping this product would be robust enough to be able to hang the thin
>>> plaster on it with no wires creating any potential weakness in the weather
>>> tightness of the plaster system. Due to the legal climate in NZ, the
>>> engineering is achieved by means other than the plaster system, cross
>>> bracing etc. While the plaster is not considered to be structural, the
>>> system will be exposed to seismic activity due to the fact that Christchurch
>>> is still experiencing pretty good shakes on a regular basis. (There have
>>> actually been over 11,000 shakes of 2.0 or more since the 'big one' three
>>> years ago)! Do these engineering numbers support my hope???
>>>
>>>
>>> http://www.cirtex.co.nz/files/file/663/Duraflow+GNG+700+Series+Data+Sheet.pd
>>> f
>>> <http://www.cirtex.co.nz/files/file/663/Duraflow+GNG+700+Series+Data+Sheet.p
>>> df>
>>>
>>> As this drainage mat is in addition to a fairly typical plaster system I
>>> am hoping the small amount of moisture which could potentially find its way
>>> through the outer plaster, across the drainage gap and into the typical
>>> plaster system would not be enough to become any issue with no typar type
>>> product. I just need to find out how to get a sample big enough to test....
>>>
>>> I look forward to reading through more of your "ranting and raving on this
>>> topic," John. and any other input would be great!
>>>
>>> Sven Johnston
>>> Sol Design Ltd
>>> www.soldesign.co.nz <http://www.soldesign.co.nz>
>>>
>>>
>>>
>>
>>
>
>
>
>
>
>
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--
John Swearingen
Skillful Means Design & Construction
2550 9th Street Suite 209A
Berkeley, CA 94710
510.849.1800 phone
510.849.1900 fax
Web Site: http://www.skillful-means.com
Blog: https://skillfulmeansdesign.wordpress.com
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