Whew…who know there was so much to know about bricks? Today we conclude this Seven-part series by taking about the all important roof.
Once all the bricks have been laid in the bóvedas, the masons begin layering the upper surface, to form the top of the roof. This system has been developed over the years to create a waterproof, strong rooftop that can double as a mirador (view terrace) or the floor of the second story.
First is Lechada
The first sealer coating is a very runny mixture called lechada. The workers mix grey cement, sealer and water, and then mop it onto the top of the bóveda. The lechada (milky-looking) liquid runs into all the cracks and crevices to seal the top side of the brick and grout.
Building up the sides; Filling in the spaces
Workers make a small retaining wall two or three bricks high, all around the roof edges, and then fill in the areas between the beams with jal (pea gravel) until the roof surface is flat, and level with the tops of the arches. Next a very wet, loose mixture of jal, yellow sand, cal (powdered lime) and cement is poured over the roof until the retaining wall is full. Small channels are included in the finish work on this layer, to direct the flow of rainwater into downspouts or off the roof onto the garden and away from windows and doors.
Workers carry buckets of the jal mixture up to the roof until a layer 6-8" deep has been poured over the entire roof.
While some of you still North of the border are imagining a ready-mix truck pumping the mixture onto the roof, that's not the way it happens here. Two men on the ground continually stir the concrete mixture and fill five-gallon buckets for the other workers. Those workers carry the heavy buckets up ladders to continually pour the roof. Occasionally pulleys can be utilized to reduce the labor required for the job, and still get enough buckets of the mixture to the roof, quickly enough.
More Lechada and then the tile
Once dry, the jal layer is sealed with another mopping of lechada. Then when the lechada is dry, the masons cover the roof with 8" square flat clay tiles (ladrillo de azotea), laid on a base of concrete.
Sealing and Waterproofing the Surface
Next come two coatings of grey cement mixed with sealer and water, followed by a finish sealer. This could be a commercial product called Fester, terra cotta or white sealer—and because of the difference it makes in the way the roof repels water, you should know the difference between the types of sealers and know which your contractor is using. .
When this sealing process is done well, the job can be guaranteed for five or six years. If it is done very well, with top quality materials and best sealers, the roof should be waterproof for about 10 years, maybe longer, although due to the effects of the sun and heavy rains, a simple additional sealer coat should be applied after four or five years.
Special thanks go to General Contractor Juan Gilberto Higuera and the maestros of The Little Company in Ajijic who explained procedures to me, answered questions and provided technical information for this article.
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