[GSBN] quoining: anyone doing it on SB construction?

Sun Aug 24 15:53:10 UTC 2014

Hi all
Indeed, in our less extreme climate here at the Southern part of Africa, I
like the idea of reinforcing the corners with a masonry element... I have
seen many old adobe building especially on some of the old farms, where the
corners have taken a beating with big chunks of missing wall at the corners.
As such I see the corners of any building as potential weak spots. 

>From a functional point of view I think straight corner pillars can work
well. So while not strictly quoining, it is a close relative. Masonry corner
pillars can also be used to help with bracing in non load-bearing structures
if the timber structure is well anchored to these elements. We typically
separate the bales from being in direct contact with the masonry work and
any moisture that the still partially curing mortar may still be giving off,
by painting on a waterproofing paint to the side of the pillar interfacing
with the bale wall and by fixing a vertical timber member along this
interface. Besides creating an easy attachment point to the sides, this
helps create a separation gap between the straw and the colder masonry and
we will then grout up the gap with well compacted cob. With the stonework,
which we make sure is solidly mortared, well grouted and stone not overly
porous, we have not experienced any moisture issues here. We have found that
by adding crusher dust to the lime sand and cement mortar mix, this helps
keeps the mortar very tight. One can also protect ones masonry from
rainwater ingress with breathable clear mat coatings.  

Personally I don't like using the various kinds of non biodegradable rigid
foam products that can be used to provide an insulation barrier within
masonry elements and so there would clearly be some level of thermal
bridging that would happens at these masonry corners. However, the solid
masonry adds to the thermal mass, which is good in our climate and so we
have not attempted to provide insulation barriers within the masonry. I
would also understand that placing such non breathable elements within walls
in general, creates its own issues with the breathability, which could
result in moisture build up within the wall. In this regard we also avoid
using HVAC systems, which in our climate, with our budgets and with our
level of technology is simply inappropriate. So have any of you any ideas
for how one could reduce the thermal bridging for such masonry elements,
without relying on such synthetic rigid foam products? Another issue I might
add besides the biodegradability of the rigid foam insulation products in
our country is that the manufacturers are still using ozone depleting
blowing agents in the manufacturing of these products! 

With brickwork perhaps a 50mm cavity will help, but this is not practical
when doing solid stonework, which both aesthetically and environmentally I
prefer to the brickwork. Our standard way of building in this country and
most of Africa is with masonry not timber like you folk in the US and
Scandinavian countries. I am also not really sure how useful weep holes are
in brickwork, as while their use is standard practice in our building trade
here in the Cape, I have often seen with existing masonry structures, that
these are the precise areas where there are moisture problems on the inside,
particularly on the wind driven weather sides of buildings. It seems that
more water actually gets driven back up the cavities via the weep holes than
actually drain out of them....or perhaps it is because the damp proof
coursing at these points is not always done satisfactorily? I also wonder
how the weep holes may negatively affect the insulation value provided by
having a cavity in a brick work wall. 

I would be most interested to hear what others think about these issues and
what other solutions people have come up with.   

regards,
Andy Horn

Eco Design - Architects and Consultants
1st floor 79 Roeland Street, Cape Town, 8001
www.ecodesignarchitects.co.za

-----Original Message-----
From: GSBN-bounces at sustainablesources.com
[mailto:GSBN-bounces at sustainablesources.com] On Behalf Of Lance Kairl
Sent: 24 August 2014 08:24 AM
To: 'Global Straw Building Network'
Subject: Re: [GSBN] quoining: anyone doing it on SB construction?

Brick Quoins on Strawbale walls.

Sorry the attached photos are not that great.

The top photo was to replicate a traditional homestead, And the lower was to
have the new extension blend in with the "free stone"
cottage.

Our method;  only done on Post and beam.
Reduce the size of the bales at the corners, and or at openings where Quoins
were to be installed.
Made sure there was sufficient room to render the straw and still allow
brick quoins to be installed. 
( usually a post adjacent to the opening or a corner post in that location
allowed the  brick ties to be fixed).

At the completion of 1st coat render , Quoins installed, And second coat
render used to fill in up to the quoins.
Yes up to, the bricks form a column , not actually stepped in and out like a
traditional quoin. The Column had the face Quoin bricks off set to the
infill bricks so the final render coats could cover the set back bricks.

How much extra work , allot .
But does it look good.
No it looks  FANTASTIC.

Disadvantages, Bricks can leak during rain events......work thru the detail,
hence rendered straw behind, have a small cavity behind the bricks, and
drainage holes.
No real thermal bridging , but reduced insulation value at the locations of
the Quoins.

Regards Lance Kairl
House of Bales
Australia.

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