[GSBN] Drainage within a plaster system
John Straube
jfstraube at uwaterloo.ca
Wed Jul 17 13:36:46 UTC 2013
The problem with this product is that the core solid plastic is a vapour barrier. In between the two fuzzy fabric layers. The other problem is that the entire structural load is being taken by glues between the fabric and the plastic core, and relying on adhesive to provide the primary and only load transfer from the skin to the backup in a seismic zone. Sure if feels strong when you are peeling it off, but in real walls after a few years of heat, cold, and moisture, that glue is not strong. Even, if it did not have all these limits it would not be that special.
What is wrong with just using nails to attach the exterior "cladding" stucco through the vent/drain gap and water barrier like a normal rain screen? This is easy to do: nail through metal lath in the exterior plaster, and have it embed in green stucco, or embedded wood furring straps. Wire, as John Swearingen described is also excellent (it just seems a little more work, but I have not done it).
Graeme's wisdom on the need for good detail is pretty sage. People forget that when you move to drained systems, the water control is mostly at one layer hidden from view: this requires some good care and attention. Adding drainage to an already functional storage system like Strawbale, however does reduce the demands somewhat as even when we have a small mistake, the water ends up on a pretty good wall!
John
On 2013-07-17, at 2:24 AM, Sarah Johnston <sarahjohnston at ihug.co.nz> wrote:
> This would be an amazing product if it came in wider than 4 inch wide rolls. This is a solid plastic barrier which snakes back and forward with a geotextile bonded very solidly to it on both sides. This would form a perfect barrier to moisture ingress while allowing the plaster bonded to each side of it to dry readily. Anyone know of a wider product like this?
>
> http://www.maccaferri.com.au/webfiles/MaccaferriAu/files/Colbond_Wick_Drain_Brochure.pdf If you scroll to the bottom of the page there is a good cross section of the profile.
>
> Thanks for your thoughts Graeme, all very good points. Once we find the best material to create the drainage, we will be able to start looking at how to make the details work and hopefully a lot of the questions will be easy to answer with the right material. Time will tell :)
>
> Ceers,
> Sven
>
> On 15/07/2013, at 11:58 AM, Graeme North wrote:
>
>> An interesting concept and one that has good potential.
>>
>> The point of this proposal is to reduce the eaves required to protect weather exposed walls form wind driven rain, but comes with the attendant increased risk to leaks around more exposed joins and openings so a bullet proof set of details will be needed.
>>
>> It is an idea worth looking into carefully, but it does need careful weighing up against other rain-screening options, or simply putting on adequate roof overhangs. I have installed cavities over strawbale, and they are a bit of a hassle to work through, but do work.
>>
>> and John you are right about earthquakes coming at us from all directions - the recent Christchurch earthquakes here had a vertical component of 2g!
>>
>> I reckon that things to consider are:
>>
>> How to attach the material to the bales so that it will carrying the weight of external plaster?
>> Does the internal "mesh" in this product deflect water towards the exterior? Always?
>> How do you deal with any joins in the material - both vertical and horizontal?
>> How do you insert openings? Face mounted joinery I can see, but not rebated.
>>
>> and as always, on site installation would need very careful attention to workmanship but that is not insurmountable.
>>
>> A robust solution to this, or a similar idea, would be great.
>>
>> cheers
>>
>>
>> Graeme
>> Graeme North Architects
>> 49 Matthew Road
>> RD1
>> Warkworth 0981
>> tel/fax +64 (0)9 4259305
>>
>> www.ecodesign.co.nz
>>
>>
>>
>>
>> On 15/07/2013, at 3:57 AM, John Swearingen <jswearingen at skillful-means.com> wrote:
>>
>>> Sven, remember that seismic loads come from all directions, and exceed gravitational loads...in our testing, the first failure location was between the foundation and the wall.
>>>
>>> John
>>>
>>>
>>>
>>>
>>> On Sat, Jul 13, 2013 at 11:52 AM, Sarah Johnston <sarahjohnston at ihug.co.nz> wrote:
>>> Thank you for your thoughts John and Ian.
>>>
>>> I believe you are both correct. I did fail to mention that it is my intention to structurally connect the exterior plaster to the perimeter beam at the top of the wall with a batten fixed through the entire plaster and drainage plane system. Once the peeling effect is minimized at the top of the wall, the 'normal' gravitational loading will be in the 'machine direction' of the fabric. My gut feeling is that this fabric would work very well in this orientation. The big question to me is the movement of mother earth. How much out of plane movement can this withstand?? I will let everyone know if/ when :) I get successful text results.
>>>
>>> Give it go.... Sven
>>>
>>> On 11/07/2013, at 12:56 PM, Ian Redfern wrote:
>>>
>>>> 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.pdf
>>>>>>>
>>>>>>> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> _______________________________________________
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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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>>>> <CA533371-6F57-4A6A-A105-6E9517FA9FC0[20].png>_______________________________________________
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>>>
>>> Sarah Johnston
>>> Sol Design, Ltd.
>>> 50A Connolly Street
>>> Geraldine New Zealand
>>> 03 693 7369
>>> sarahjohnston at ihug.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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>>
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>
> Sarah Johnston
> Sol Design, Ltd.
> 50A Connolly Street
> Geraldine New Zealand
> 03 693 7369
> sarahjohnston at ihug.co.nz
>
>
>
>
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John F Straube
jfstraube at uwaterloo.ca
www.JohnStraube.com
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