BELIEVE YOU CAN » A Straw Bale experience!

A Straw Bale experience!

Straw bale building is quite easy and a practical solution in for people looking to build a low-cost natural home.

Raising Bales

The secret of Lime or Cal is a little harder to learn. Even though lime has been used for thousands of year the best lime of all is water proof, hard smooth surface as plaster and new with olive oil and porcelain!

I have been working on two large straw bale workshops at an eco-village in Portugal. These are big structures, 500m2 area and up to 10m height. Their technique relies heavily on machine power to move sections or to mix earth, straw, lime for plastering. One advantage is you can plaster the wall of such a building in one day.

I also recently built a timber frame straw bale donkey house all by hand. This is more natural building. It was run as a teaching and skill sharing workshop and this helped cover the cost of the materials. At the ecovillage project this is different. Labour is mostly brought in and so the cost is high.
Straw Baling Methods

These are some of the methods I learned:

Lime plastering on straw

The bales of straw must be compressed and holes filled to elliminate air gaps. Keeping the straw dry at all times is really essential.

In the farm environment we put chicken wire net on the bale wall to protect against small animals and make it easy to plaster with clay. Even so when our donkey got hungry he tried eating the wall, until it was fully rendered!

Earth plaster is applied direct onto straw. wall sections can be pre-fabricated and a wash of pure clay then 1cm of clay+earth+straw is applied to the sections which are layed flat on the ground.

When the sections are build together on this goes a half clay half lime mix and then a final coat of lime.

Plastering with Lime

There are many types of lime. Most common is hydrated lime

and hydrolic lime. Hydrolic lime is more specialised and used for its water resistance. Traditionally “cal viva” or live lime that comes in bags of rocks was used. This reacts on contact with water and must be allowed to stabilise before use and mixed as a paste to the sand+straw choice of materials.

The beauty of the lime used at Tamera ecovillage is that it is both water proof, hard and smooth almost shiny finish. This is by far the best lime plaster I have seen anywhere in Portugal. What makes it special is the inclusion of olive fibre pressing and porcelain dust.

Lime on clay plaster - inset is final lime + porcelain render

This makes a tough veneer like render as smooth as well very fine plaster, effectively the best and better than anything I´ve yet seen in Portugal.

thin wet coat of straight clay direct onto straw
1 cm of clay + sand + straw
1 cm of half lime (+olive oil fibre) half clay
4mm of lime special + porcelain plaster

This product can be gotten from www.fradical.pt. I recommend it and will be using this myself from now on.

Before I tried using boiled prickly pear cactus added to lime to make it water proof. We also have added linseed oil but nothing compares to the olive fibre.

Building a Straw Bale house is practical + affordable

Let me know if you are into Straw Bale building. I will keep you in touch with what I´m up to and will contact you for the Spring seminar.

If you like the idea of creating or strengthening a straw bale builders network here in Portugal please get in touch!

Jonathan Eveleigh

irene freeman

August 3rd, 2009 at 6:27 am

Wht happens if there is a fire-Is the straw house protected against fire and rain etc??:

Matt

October 2nd, 2009 at 9:08 am

Hi. I am in Spain and am curious if you are working on any projects right now? I would like to come participate, help out, and learn the techniques. I am currently living in Andalucia, Spain, so it would be a pretty short distance for me to come there. Thanks.

Alvaro

October 21st, 2009 at 2:41 pm

Hi Jonathan,
I reside in the UK but am thinking of moving back to central Portugal
and buy a building plot. There I would like to build a straw bale house of about 120 m2. Do you have information about building permission for this kind of construction? Is there any place I can get more information/assistance in Portugal?
Thanks for all the info you could provide.