Light Clay

The framing of the house created some interesting areas that were challenging to fill using straw bales, so we decided to do a little light clay instead.  In the upper level, the framing of the roof joins in with the framing of the floor, leaving a narrow wall space that widens out with the curve of the roofline, so filling this oddly shaped wall space with light clay was a great solution.

Light clay is a mixture of loose straw coated with clay slip and packed into a form.  The form is removed right away to allow for quick drying time, and there you go… a nice flat straw surface solidly held in place by the clay.

The process is fairly simple.  We spread loose straw on an old piece of plywood, mixed up some clay and water into a nice thick slip, poured it over the straw, and tossed it with a pitch fork.  We were looking for an end result of long straw that would stick together when squeezed, with no clay dripping or running off, but with the colour of the straw no longer golden.  Like a salad dressing… lightly coated.

 

We did the first foot of wall, adding screws or nails into the framing to give a little something for the straw to tuck into, and packing it in securely but not densely.  After we took the forms off, we let it dry out for a week, then did the rest of the wall up to the window bucks.  Our wall section widens out once it gets above the roof framing, but we didn’t want to fill the whole space at once and risk the centre staying moist for too long.  We put the forms back on higher up and did our second lift in another few hours.

This was the first time I had done any light clay, and I know it is another whole natural building method in it’s own right.  We have helped some friends build their house with chip slip, which is the same as light clay but uses wood chips instead.  The mixing of clay and straw has been used as an infill material for timber framed buildings from at least the 12th century in Germany and elsewhere in Europe.

It was really great to so easily utilize a variation of natural building in our predominantly straw bale house.  I think we would have done more in some of the other awkward spaces, but the timing of the summer sun was a bit late for ensuring a complete drying out of the clay slip, and we ended up making lots of small oddly shaped bales to stuff with.  But that will be another post~ the results of baling above this light clay wall and then plastering over the whole thing was quite positive.  The flatness made for a lovely plastering experience, compared to the lumpyness of the bales… but that will be another post as well!  Stay tuned as I catch up on a busy summer and fall of building.

1 Comment (+add yours?)

  1. macwestk
    Nov 23, 2017 @ 05:23:56

    Very interesting. We did our power shed in light straw clay and loved working with it. On another topic, would you mind sharing your experience in finding house insurance for your straw bale house? A group of us on Gabriola who have houses built using one or more of LSC and slip chip, blown cellulose and natural plasters and straw bale have been discussing insurance and looking for amenable insurers for alternative and natural builds. Any help would be appreciated.

    Reply

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