Construction 6: Roof

 18 January 2015

         

  If I had to reduce to a single phrase the Mexican art of house building, as we have come to know it, it would be this: ‘Use what you have, to cobble up what you need, to make what you want.”

 

            Scrap wood, for example. Lalo has brought with him fifty or sixty planks that he owns and that travel with him from site to site. We have purchased lots of beams in assorted sizes and a number of flat pieces that start as paneling but soon devolve into any number of shapes and uses. If a brace longer than any of the existing boards is needed, two pieces are laid end to end, two more sandwich the joint and are nailed into place: Voilá, a long brace. A short brace is produced with a handsaw. Scraps are tossed to one side and eventually create large piles: one down by the entrance road, one up by the bodega, and assorted remnants of formerly long pieces lie here and there where they have been sawn off. If a master carpenter needs a shim of a certain size, he points to where it will go, sketches it with his hands, and in an instant his helper finds the piece he needs and tosses it up to the maestro. If the piece is a little too big, the sharp edge of a trowel or one of the omnipresent machetes lops off a hunk or shaves it to perfection.

 

            If a ladder is needed, two long boards are laid side by each and one of the assistants nails on cross pieces. Almost before the request as ceased to echo, a ladder of the perfect size, sturdy as the top of the line at Home Depot, is in place and workmen are scrambling up it. If a ramp is needed for the bucket brigade to bring wet cement to where it needs to be poured, presto!, a ramp is in place. If plasterers need scaffolding so they can slather the upper section of a wall, the verticals, the cross braces, and the floor planks are dug out of the storage piles and —bang, bang, bang—three men with trowels are throwing mud against the wall.

 

            It is not that there is a lack of tools. The maestros bring their own. Every master carpenter has a hammer stuck in his belt from which also hangs a small sack of nails. There are enough trowels and mortar-mixing boxes around to fill the need. First thing every morning Ermilo unlocks the work shed and out c

ome a couple of buckets stuffed with hand saws, pry bars, wire-twisting tools, rebar clippers, and chisels. There are few power tools too: a chain saw, a power planer, a vibrator tube to shake poured cement so that it settles firmly into corners and niches. There are three extension cords, two of them ending in bare wires that are twisted together to bring power to the far corners of the site from the plug on the porch of the casita. The cobbled cable shorted out so often that Linda and I sprung for a new 20-meter cable from one of the three small Construrama stores that are sprinkled around San Pablo. But most work is done by hand, and most of the component parts are crafted on site.

           

            Though there have been many points of discussion in building this house, on one thing we have all agreed: it has to have a roof. Roofs in Oaxaca come mainly in three styles. There are flat ones, but they invite puddling during the rainy season, and standing puddles eat away at all sorts of materials, so that—eventually—leaks are guaranteed. OK, no flat roofs. There are simple sloping roofs, so that the water runs off in a single direction and falls to the ground where it can rut the down-sloping yard in predictable, unidirectional ways. This sort of roof is called a techo a una agua. Most people prefer a techo a dos aguas, which means the roof has a peak in the middle so that the water runs off on both sides. Our casita has a techo a dos aguas, sloping to the front and the back of the house. The water drips off the roof tiles into the two hanging gutters, and descends on rain chains to the collecting basins, from which gravity delivers it to the cistern under the porch.

 

           

Cynthia, it seems, likes angles. As do we. The dining room of the casa skews at a 60 degree angle from the kitchen. The bedroom wing T’s into the living room. The laundry room and pantry angle off of the kitchen and shlump into the back patio.

 

            Our under-construction main casa seems to be developing a techo a 8 aguas. We’re not yet sure how many collection basins there will be, but the men are as I write trenching for pipes to carry the aguas to the 100,000-liter capacity cisterns under the front terraces.

 

            Mexican roofs come in 5 basic materials.

 




            (1) Thatch: favored in the lowlands and in jungly areas as roofs for vernacular (i.e., poor folks’ traditional) architecture. They dry quickly, let lots of air circulate, let smoke and heat escape, and provide convenient nesting sites for otherwise homeless insects, lizards, and spiders. Not very useful

up here in the scrubby lands with weather that is 9 months dry and 3 months very wet.

           

            (2) Corrugated tin: cheap, impermeable, easy to put up, noisy when it rains, used widely for sheds and small basic houses. We have put lámina on our bodega, the garden shed & detached storage closet along the back fence. Cynthia had the men put a brick edging around it, so from below it cheats and looks like it might be a brick or tile roof.

 

            (3) wood: common in the forested lowlands, planks laid close together and joined with .... stuff (asphalt, adobe, patches of plastic, whatever). Popular in the Michoacán highlands where the Tarascan Indians use planks to cover their houses, and for lowland houses in the former British areas like Belize and the Mosquito Coast. Not practical for us.

 

            (4) concrete poured over some sort of framework (pre-fabricated panes, wood planks, carrizo poles, nets of rebar): great for sustaining weighty add-ons, like water tanks, or solar heating panels. We’ll have this type of roof under our water heating gizmos.

 

            (5) Baked Mediterranean-style ceramic tile over any of the above, in just about any combination. Yup, that’s us. Mostly.

 

            The casa’s front and back porches are getting baked tile over carrizo. Ditto the front and back studies, so the lines will flow smoothly with the porches. Says Cynthia.  First they erect a basic structure of beams resting atop either brick walls or freestanding wooden pillars. We have both: walls for the house, pillars on the porches. Resting on the support beams comes a lattice-work of thin beams—thick poles, really—supported by the beams. Over these the carrizo is laid and lashed into place. Impermeable fiberglass glass sheets are unrolled over the carrizo, and tacked onto the thin beams to hold them fast. Over these sheets the tiles are laid in overlapping rows. From underneath, these roofs look like rustic carrizo. From on top they look like European-style tile roofs. From the middle, through which the rain would like to pass, they look like an impenetrable barrier. Or so we hope.

 

            The corridor separating Linda’s and my studies and bedrooms from the public rooms is getting a sloping concrete roof, except for a line of glass tiles that let light fall on the bookshelves that will line the corridor. We have decided to defer thoughts about mold.

 

            The public wing—the living room, dining room, and kitchen—is also getting a tile roof. The beams rest on top of the walls. At least they appear to be resting; so far no hopping about, though we haven’t had a seismic tremor for a few months now. Insulating, impermeable, rigid structural panels rest (see above) on top of the beams. A reinforcing web of steel rebar is laced over the panels. A 5-7 cm layer of concrete has been laid to cover the rebar and seal the panels. The cement was all mixed by hand, of course, carried in buckets up rickety ladders to the roof, poured into place, and smoothed by hand trowels. A bucket brigade of six kept the cascade flowing. At sundown after the cement had been laid, the men hauled hoses up to the roof and wet it down to keep it from drying too fast and cracking. Another contingent appeared the next morning at first light to repeat the process. And so on for a couple of days. The tiles should go on this Saturday or maybe on Monday, a process that should take several days.

 

            Building the casa’s roofs, like building the foundations, the cisterns, and the external shell of the casa, requires swarms of workers, tons of rebar, many tons of cement and gravel and sand, truckloads of tiles, a small forest of planks and beams, buckets of nails, and an intricate and sophisticated dexterity of sequencing that keeps everybody working and the parts growing in precisely the order that makes them all possible, one over the other, from bottom to top and then from top to bottom. It is ensemble ballet, with a choreographer (Cynthia) and a director/conductor (Lalo), ov

erseeing a corps de ballet of up to thirty dancers. I mean workmen, maestros and assistants. Building this complex of roofs requires knowledge of engineering, materials, and physics. It also requires mastery of the art of scrounge and a total disregard of cautionary behaviors.

 

            Linda and I are in a continual state of amazement at how hard these people work, how talented they are, how efficiently they manage the complexities of all this, and with how little they accomplish so much.

 

 

 


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