Lenter: chhat dhalai from shuttering to tarai

The diameter and the bar count belong to the structural drawing, and no counter can supply them. How that arithmetic is done for a house of a given size, and why an engineer has to do it, is on the sariya for a 1000 sq ft slab guide.

The cover height comes off the exposure class the drawing names. Cover is the concrete between the steel and the finished face of the member, and IS 456 asks for 20 mm of it in mild exposure and 30 mm in moderate, with larger figures as the exposure gets worse. The block holding that gap is the one item on the order whose entire job is to stay the same height while wet concrete goes in around it, and IS 2502, the code for bending and fixing bars, is what it answers to. The figures class by class are on the cover block guide.

The cement type is the word in the statutory block on the bag, OPC, PPC, Portland slag or composite, and it is read against the drawing before anything is mixed. Which of them a reinforced pour may be made with, and the one type kept off it, is on the cement for a roof slab guide.

The fourth is the day itself, and it is the one a shop can actually move. A slab is poured in one continuous go, so a house that runs short of tar at noon has a problem no delivery can fully undo. That is why all of it is counted before the morning and not on it.

A lenter order arrives on the phone and it is written down in the same pieces every time. The diameter and the count for the cage, bar by bar. The binding tar and the cover blocks that go with it, because a cage is not a cage until it is tied and stood off the shuttering. The cement type as it reads on the bag, and the bori count against it. The day the mixer comes. And the village the vehicle has to reach, which decides whether the load goes on a tempo, a tractor or a truck.

The sariya and the cement usually leave on two different days, and that is deliberate rather than untidy. Steel can stand on a site for a week while the cage is being cut and tied, so it goes early. Bags are wanted closer to the pour, because cement waiting in a damp corner of a half built house is cement nobody wants to open on the morning of the dhalai. One order, one call, often two vehicles.

Two things are worth saying out on that call even though they are not material. Say the day the mixer is booked for, because that is what the whole load is timed against. And say the village by name rather than the block, since the last stretch of road is what settles the vehicle.

Tarai starts on the day of the pour and runs somewhere between 7 and 21 days, and which end applies is decided by the bag. Nuvoco prints 7 days. Shree Cement splits its own figure, 7 where the bag reads OPC against 10 to 14 where it reads PPC or PSC, and puts a roof slab in hot or dry weather at 14 to 21. Each of those is a minimum, so the longest of them satisfies the rest. The tarai guide has the period each maker publishes, maker by maker.

The shuttering comes down on a separate clock. Nuvoco puts the vertical shuttering of a column, a wall or a beam side at 16 to 24 hours, a slab bottom at 3 days with the props put back at once, and a beam bottom at 7 days, all of that above 15 degrees. So there is a stretch where water is standing on top and props are still holding underneath, and tarai is not a pause in the work. Whatever goes up after the slab reaches a site that is running, which is why the next delivery is worth fixing on the lenter call itself.