[Cob] (Cob) termite protection of earth floors

[Simon Matthews]

Thanks for your experiences Barbara, there is some very interesting
information in what you have written.

We too are building with light straw clay walls around a timber frame.
To date we have built a 6 metre by 4 metre (18ft x 12ft) room on the
side of a shed as accommodation and to test out the building methods and
materials for when we build the main house.

One of my big nightmare scenarios is termites boring through the floor
and eating the furniture. The termites are pretty determined here and
are very adept at getting to softwood.

For our room we placed at great expense a layer of commercially made
pyrethrum impregnated plastic sheeting directly on a smoothed subsoil
clay base and then four layers of soil and sand mix. To this we applied
three coats of unboiled linseed oil. The floor was quite porous so
really soaked the linseed oil in. The floor has been fantastic, no
problems with damp or termites and it is really strong and durable.

I can't say for sure if the plastic has done anything as we have done
the same treatment to sections of the tin shed floor which abuts our
room without the plastic sheeting and have not had any problems with
damp or termites although we do store all our valuable timber on some of
the plastic sheeting and not directly on the ground.

After about eighteen months of use we 'refreshed' the floor with one
more application of linseed oil. I know what you mean Barbara about the
smell. We also had the problem that the Linseed oil didn't soak in and
remained wet on the surface. To counteract this we put newspaper down
over the whole floor and left it there for a few weeks while still using
the room. The newspaper worked a treat at soaking up the excess oil. 

Next time i will thin the oil down or might try to get the Bioshield
Hard Oil. Do you know what type of oil it is, is it based on Tung Oil?

The reason i am asking about the Boric Acid is a friend of ours is just
starting to build a straw bale house and will be living in a shed while
they are building. They saw our earth floor and loved it, unfortunately
they will not be able to use it in their house due to building
regulations but want to use it in the shed without paying the exorbitant
price for the plastic sheeting we have used. I am also interested in the
extra layer of protection that putting Boric acid in the floor mix
should give.

Simon