[Strawbale] Strawbale and brick walls

[Rob Gort, Bouwcarrousel BV]

Hi Marcus

It depends also of your design (e.g. did you think about a good roof overhang, and did you imply measures to prevent moist crawling up from the ground level into the bales and bricks?), the local weather conditions (heavy showers, strong winds with rains, long periods of fog etc.?). When your design is good, the masonry work is done well (without cracks, holes etc.) and your outside lime layer is also being plasterd without cracks, it should function allright.
But, when you have your doubts in any of these respects, then your architect has a point, especially when the brick wall is rather thick.
When water / moist can enter the wall system (and bricks can absorb huge quantities) because there's a leak somewhere (e.g. caused by a neglected crack in the lime plaster) than surely a problem can arise. Because the brick wall is so thick, it 'll take substantial time for the damp / moisture to disappear out of the wall system again. When this time period is more than about a week, the rotting proces could start (also depending of the temperature, the quality of the bales etc.). 
You could think about putting a damp foil in between the straw bale insulation wall and the brick wall, and also some space (a couple of cm's) between this foil and the brick wall, and make about 2 till 4 small ventilation holes in the brick wall of 1 cm diameter each, every time repeating this at a distance of say every 3 m, so a bit of wind can enter behind the brick walls (this is more or less the Dutch way of building with masonry work). This is offcourse only a good idea, if the brick wall does have no real insulation function.

Succes
Rob Gort
Bouwcarrousel bv
www.bouwcarrousel.nl



  ----- Original Message ----- 
  From: Marcus 
  To: strawbale at amper....muni.cz 
  Sent: Wednesday, September 12, 2007 8:53 PM
  Subject: [Strawbale] Strawbale and brick walls


  Hi there,

  I am helping a friend who is planning a new two storeyed brick/strawbale house with an earth roof. We have knocked down an older building on the existing site and have a lot of bricks. What he has in mind is to use the bricks to build the load bearing part of the structure and use strawbales for insulation. So the walls will be very thick.

  The query is... that an architect friend said he wouldn't recommend putting strawbales in contact with the brick wall as moisture will wick from the brick walls into the straw causing a damp problem. He based his theory on the fact that wooden beams in Germany are known to be susceptible to rot when they go through brick walls. I can imagine that with an older house with
  insufficient damp-proofing, moisture can wick up the walls to the height of the beams and cause a problem BUT... with a new house, with good damp proofing, I can't see where the moisture would come from.

  The house would have earth plaster on the inside and outside (with a limewash finish) so there wouldn't be any barrier to stop  vapour going through the walls.

  Does anyone have any ideas about this or have heard any experience of people cladding brick houses with straw.

  Any ideas would be greatly appreciated.

  Marcus 

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