Construction

The kit behind a slab pour:

block walls go up a course at a time, but a concrete roof is cast in a single day, and that day sets the shopping list. Building materials carries the cement, sand, block and rod that end up in the slab. The props that hold the formwork up and the frames a mason stands on sit under stairs and scaffolding, with the stepladders and extension ladders that come out for the finishing work. Tools splits into manual tools, the trowel, float and plumb bob of a mason’s kit, and electric tools such as rotary hammers and angle grinders. The wheelbarrow and the two-wheeled hand truck that moves cement sacks are under wheelbarrows and carts.

Mixer drums by the sack, props by their height:

those two measures decide whether a machine fits the job. Mixers are sold by how much cement they take per load. A half-sack drum suits mortar and small pours; a one-sack drum is what a contractor brings to a slab, because it takes a whole bag of cement at a time. Many of the petrol mixers that rental yards send out run on a Honda engine. Telescopic props are sold by their height range, so measure from the floor to the underside of the formwork before buying, and pick props that reach that height without running out to full extension. Scaffold frames from different systems do not fit together, so a set has to match itself, or match what you already own.

Renting against owning a mixer and a set of props:

for a family pouring one roof, renting wins. A one-sack mixer rents for around Q300 a day, and a new half-sack petrol mixer costs a little over Q4,000, so about a fortnight of rental pays for one of your own. Props work the other way round. A new telescopic prop is about Q250, and a rental yard can set a minimum order of more than a hundred, which is more than a single house needs. That is why used props and scaffold frames pass from one small builder to the next: straight steel tube has little to wear beyond its thread and pin, so a complete used set sells not far under new, while a used mixer is worth what its engine and drum are worth.

Bent prop tubes, worn ring gears and lighter batteries:

a used prop should slide its inner tube freely, lock with its pin and turn its collar along the whole thread. A bent inner tube or a stripped thread makes it scrap, and props listed without their pins are only part of a set. Sight along each scaffold tube for bends and look at the welds where they meet. On a mixer, start the engine cold, run the drum with a load in it and listen at the ring gear and pinion that turn it: broken teeth knock, and a drum pitted with rust or with concrete set hard inside was left unwashed after a pour. Copies of the batteries for the big cordless brands circulate and feel noticeably lighter than the real thing, so buy a cordless drill with its own battery and charger.

Props and a mixer once the last slab has cured:

are worth more to the next builder than stacked in a yard. Give the number of props, their height range and whether every one has its pin; for scaffolding, the number of frames, their height and how many cross braces and boards go with them. For a mixer, state the drum size in sacks, the engine make and whether it pull-starts cleanly. Photograph the threads, the welds and the inside of the drum. Someone coming from Sololá or Chimaltenango for a mixer will want to hear it start and watch it turn a load before agreeing a price, so have a few buckets of sand and water beside it for the test.