Bajareque Cabin Build – Part 3

Bajareque Walls and Earthen Plasters

Ventura, a local expert in traditional natural building, mounds up sifted dirt for the earth mortar, excavated directly from where we’re building. The rocks in the background will also help fill the walls.

An end-section of the wall. From left to right we have the door-frame, well oiled, a wooden spacer to separate the door-frame from the corner post, and the corner post, to which the lengths of bamboo (note that this bamboo isn’t hollow in its middle) have been strapped using both a local vine and some sisal string.

The wall goes up – with this method we placed about 50cm of rock and then flung the earth mortar at it using a trowel. The mortar contains sifted earth, pine needles and pumice sand.

Hands are the best weapon for flinging mud, and it works best with an opponent:
The higher up you go, the less you can fling as it shakes the whole structure – instead it works better to lay the mortar, place a rock in the mortar and then push more mortar to cover the rock and the bamboo.

The window frames – oiled cypress boards, to be filled later:

A trowel helps for the details:

This stuff is magic – pads of prickly pear cactus (known locally as nixte’en – nish-teh-unh – also tuna, or nopal), sliced and diced into 1″ cubes then fermented in water for one week:

After a week, strain out the scum and floating debris, and you’re left with an extraordinary transparent gel that works as an excellent binder and waterproofing agent for natural plasters. The gel lasts for up to a month before losing its strength.

But be careful not to lose it all – if you happen to slop even a little of it over the edge of the container, it’ll start pulling the rest of it with it and in seconds a giant transparent snake of goop will slide itself out onto the floor. It reminded me of the special effects in the movie “The Abyss”.

Applying the 1st coat of plaster:

We used local clay (25%), sifted horse poop (20%), 1/4″ white pumice sand (55%) and prickly pear juice. It smelt pretty foul at first but the odor soon disappeared.

Beautiful.

On the outside we put a lime and prickly-pear juice render to prevent rain-splash damage near the base of the wall. The earthen plaster above it comes from recycled adobe bricks, which provide a near-perfect earthen plaster ready mix! We just added a bit of sifted horse poop (for the fibre) and some prickly-pear juice (for adhesion).

A stick insect enjoying the earthen tones:

Thanks for visiting, see my next post for more.

 

 

Bajareque Cabin Build – Part 2

The Roof

The rafters and ridge beam come from a local tree called tzajokché (pr. Tza-hock-chay), which needs chemical protection from bugs but is otherwise ideal due its long length, straightness and low density. It’s also local and quickly renewed if the harvest is well managed. Another popular tree for this is lema’, which is even lighter but more prone to insect attack.

Here’s the wall frame and most of the rafters up:

The roof stringers are the same material as the wall straps: Mexican weeping bamboo. However, we treated these ones in a solution of boric acid and borax to keep bugs and mould out. The bamboos in the wall don’t need any chemical protection because they’re encased in mud, which keeps out both insects and moisture – even killing what bugs might have gotten in during the build! I’ve seen 50-year-old houses demolished and the bamboos were as good as new.

So next comes the palm thatch from the coast, about 40 cents per leaf – this truck can carry about 2,500 of them:

And a human can carry about 25 of them! I consider myself tougher than most but I couldn’t carry more than 20. This guy, a 50-year-old father of six, carried more this day than any of the younger guys, many of whom carry building materials as their full-time job. I have utmost respect for their strength, stamina and resilience.

Next comes the thatching, a job best done in cloudy weather as it keeps the palm leaves fresher.

Each palm leaf is tied on using the outer edges of the leaf itself. A top thatcher can attach about 500 leaves a day with a couple of helpers to prep the leaves:

Looking out from under the eaves:

Lunch break – tortillas, chile, beans (yum!) and a 3-litre bottle of Guatemalan cola (yuck!):

And it’s done:

It’ll gradually turn grey over the next month, and it’ll weigh around half what it does at this point too – we had to put in extra bracing to help the rafters cope with the wet weight.

Next comes the walls – in part 3…

 

Bajareque Cabin Build – Part 1

We began building in early 2012 – this is the first of the cabins for The Yoga Forest, a yoga and permaculture retreat centre in San Marcos La Laguna on Lake Atitlan Guatemala.

The view from the cabin-to-be:

Starting the cut:

…and fill:

Excavating for the reinforced concrete foundations:

While reinforced concrete isn’t very natural, it was the only foundation that I and the lead builder felt comfortable with on such a steep slope. I’ve since learnt more about natural foundations and how to work with slopes so the next cabin (immediately next door) will have a lot less concrete and steel in its foundations.

We hit some hard dirt in some of these holes, which at least makes for a solid foundation, if not an easy dig:

One of the concrete footings – 1.75m deep to eliminate the effects of soil creep on such a steep slope:

The foundations complete, for now
– we intend to dig a french drain one day but at this point we just wanted to get the cabin up:

Now we can start with the more natural part of the build!

The structure is bajareque (pronounced ba-ha-reck-kay – read my earlier post about it here). In short, it’s a hardwood post frame, strapped on both sides of each post with many lengths of thin bamboo that are tied on with a fibre extracted from the leaves of the Sisal agave cactus. The void space is then filled with rocks and an earthen mortar, making a very affordable, natural and earthquake-resistant house.

They can be very beautiful too and that’s what we’re planning for this cabin.

Here’s the frame up and the bamboo going up:

This post is getting a bit big now, so read on in Part 2…

A bajareque wall with the Appropriate Technology Collaborative

The Appropriate Technology Collaborative‘s 2012 visit to Guatemala brought 17 volunteers from around Michigan to Lake Atitlán, where they installed a solar electric system to power the computer lab at CECAP‘s vocational training centre in Santa Cruz La Laguna, and built an exterior wall out of bajareque at the nursery school of San Marcos La Laguna.

The problem – a neighbour’s land where the kids would escape!

Before

The solution: a bajareque wall made from hardwood posts, bamboo, rocks, mud, natural rope and elbow grease!

Mixing the mud – many feet make light work.

Applying mud to the wall.

Applying the first layer of earthen plaster with a large wooden trowel.

Project finished! Our local team of natural builders – Juan, Noé, Ventura and Chepe.

And the whole crew – the volunteer team from the Appropriate Technology Collaborative

The whole project was a great success and we’re looking forward to making more such walls in the school and in other public spaces with future ATC volunteer teams. We hope to document the process so that others can copy the technique.

With the help of a pair of longer-term volunteers, this coming week we’ll be putting a small tin roof to keep the rain off, a lime and prickly-pear plaster to defend the bottom of the wall from raindrop splash-damage, and a clay plaster for the rest of it. I shall add photos as it happens.

To see more info and photos on the trip, check out the ATC blog by John Barrie, ATC’s founder and director, and also Tina’s blog.

Bambareque

Bambareque is a fusion of bamboo with the traditional bajareque buildings of the americas.

Bajareque is the wattle and daub of the americas – mud, sticks and stones combined to make simple one- and two-storey buildings. Its most endearing features are its low-cost, renewability, earthquake-resistance and ease of construction.


Cross-section of a bajareque wall from the western highlands of Guatemala

The combination of materials in bambareque is not original, but the name is. I built my first bambareque building – a composting toilet – in 2008, to see if it could add some of the benefits of building with bamboo to the excelent qualities of bajareque. It’s still in great shape and so, due to its use of a cheaper and more renewable resource and having better seismic resistance than traditional wood-framed bajareque, I think it deserves its own name.

In this area (western highlands of Guatemala), bajareque buildings are built by first assembling a frame of hardwood posts. A thin bamboo (Mexican weeping bamboo) is then strapped horizontally onto both sides of the uprights using wet agave fibre ties (aka maguey). Pine needles are draped from the bamboo before filling the cavity with rocks and a mix of mud and pine needles. The mud mix is then applied as an earthen plaster to seal and preserve the organic materials within.

Earthen plaster applied over a bajareque frame

I’ve yet to visit them but I have heard of 500-year-old bajareque buildings in Guatemala that are still standing, although most don’t last that long. Before the 1960’s, most rural dwellings in Guatemala were bajareque, then adobe took over until that too was superseded by reinforced concrete and cinder block. While block and adobe appear more substantial, and are generally more desirable to most rural Guatemalans, bajareque has superior resistance to earthquakes and it’s also considerably cheaper. Ironically, bajareque has seen a revival among wealthier central americans for building their weekend homes, which are often finished to an exceptionally beautiful degree.

A typical bajareque house in El Salvador – note the bamboo rafters.

Replacing the wooden frame in bajareque with bamboo makes it even cheaper and more ecological. The main difference it makes to the building is due to the size of the bamboo – it’s a lot thicker than the hardwood posts they usually use, which are normally three to four inches thick at most (8-10cm), whereas building-grade bamboo is about six inches in diameter (15cm). This creates a much larger cavity, and thus more work to fill it, but it also creates a more insulated wall.

Another difference is that bamboo doesn’t like being buried in the ground, since it’s more vulnerable to humidity, insects and fungal decay than the traditional hardwoods used for bajareque. The bamboo is pre-cured in borax and boric acid but the moisture in the soil will eventually leach that out. My original solution to this problem was to bury it in cement but I’ve since come up with several other lasting solutions:
(1) insert shortened hardwood posts soaked in burnt oil into the base of the bamboo uprights and insert the other end of the stick into the ground;
(2) bury large rocks into the ground (>60cm deep) leaving 10cm proud, glue rebar into them with epoxy, then bend the rebar into a hook, drop the bamboo onto the bar till it sits on the rock, and then fill the bamboo’s base with cement;
(3) tie the bamboo to a reinforced concrete foundation and fill the base cavities with cement.

Four years later, I’m more convinced than ever that bambareque is a sound building method and hope soon to begin building a bambareque community refuge in San Marcos La Laguna, for families whose houses are at risk from from landslides during Guatemala’s heavy rainy season. The venture is funded by The Appropriate Technology Collaborative, who is also bringing a team of volunteers to help build and document the design.

Another project currently underway is a bambareque cabin in The Yoga Forest, a retreat centre and edible forest garden in the hills above San Marcos La Laguna.

For more information on bajareque, check out the World Housing Encyclopedia’s “Vivienda de Bajareque” by Lang, Merlos, Holliday and Lopez.