Saturday, December 22, 2007

Building with adobe blocks

When we arrived here a week ago that's what we saw. Its a very imposing structure and the picture doesn't give a good sense of the scale of the building. Along each side of the building there are two apartments that will eventually house 2 "families" of orphaned children. Each apartment is completely self contained with kitchen, living area, bedrooms and laundry facilities. The intent is to have 8 kids per apartment and a foster parent couple in each apartment. There are 2 small "bachelor suites" at the front centre of the building. The back of the building houses a huge meeting/eating area with an institutional size kitchen at one end and a large workshop at the other end. The upper level has some smaller apartments for volunteers and the intent is to eventually house some of the older orphans in that area as well. The centre of the structure is a large open courtyard with all of the apartments opening onto it.

It has taken 3-1/2 years to construct the building to this stage using a crew that currently numbers around 20. There's a lot of work to laying adobe blocks. The crews only work from about the end of November to late April because that is when their gringo volunteers are available.

Those walls are well over 14" thick. An adobe block starts out life as the local red clay mud. In the case of this construction site "mud" is actually pretty dry dirt that is run through a hydraulic press to convert it into a block about 5" high x 14" long x anywhere from 3-8" wide. Then the blocks are laid crosswise side by side to slowly build up a wall. Then the wall is covered with successive layers of concrete. One of the really neat features of adobe construction is its ability to heat sink. Because there is so much mass in the structure it stays relatively cool during the day and relatively warm at night. Noticeably warm first thing in the morning and noticeably cool during the heat of the afternoon.

I got to participate in several distinct phases of the construction process, from making blocks through placing them to forming for a roof and finally pouring the roof. The traditional way to make blocks is to form mud into blocks and wait a month for the sun to completely dry them. This project uses a press so we could make blocks for a half an hour and place them for the rest of the day. The traditional way to make a roof used to be to lay poles across the span then place clay tiles across the poles and then to pour concrete on top of the tiles. That evolved into using poured beams to replace the poles and now the usual practice is to pour the entire roof with integral beams. We formed the surface of the roof, then laid chicken wire so the finish stucco would have something to carry it, then laid 2'x2'x8" styrofoam blockes to create voids and beams, placed steel in the beam areas and finally formed the sides to create a slab roof that is about 4" thick carried by 12" deep beams. There is probably 60% of the roof volume taken up by the styrofoam so it is not as heavy as it appears but still a lot of overhead concrete to form and place.

Since I have some experience with pouring concrete - actually a surprising amount of experience once I start into the process - pouring the concrete was the least educational part of the whole process. I was glad to see that they didn't adhere to tradional processes for pouring the roof. There is a 1/4 yard mixer out behind the site that runs constantly during the day with one man continuously shovelling sand through a screen and another running the mixer non-stop. He dumps into wheelbarrows and the mud goes off to grout blocks or get trowelled onto walls. I've seen them lifting concrete to the roof using a pail and a rope so I had visions of us lifting 6 yards of cement to the roof. I was very pleased to hear that there would be a pumper truck onsite for the pour. The picture is of the truck set up to pour the roof of the bell tower.

We also poured the sidewalk yesterday. 80' of sidewalk, 4" thick & 6.5' wide when the temp is over 80 degrees - you don't have much time to work the surface in those conditions. Fortunately the water was on yesterday or we would have lost about 1/2 of the sidewalk pour. It was a near thing as it was. The local guys are so good with concrete it is a treat to work with them and learn from them. They use so much "cemento" in all their construction and they know what they can get away with. They use too much water for my liking so they end up with a lot of cracks but they are the local experts and there may be some other problems that they are avoiding with the excess water.

And on the subject of local expertise - - concrete counter tops and concrete sinks. You have to see them to believe them. They polish the concrete so it looks like granite and the sinks are integral with the countertop. This stuff is like Corian on steroids - looks great and is indestructible. It would be great for a cabin or for a laundry area but maybe a little "heavy" both visually and physically for most kitchens.

For more information this is the website for the project:

and this is Bob Masons website that deals with the orphanage project from its inception:

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