First Class, Second Class, Third Class: What Kiln Grades Mean For Your Wall

Two Bricks, Struck Together

A brick class is a performance band: a minimum crushing strength and a maximum water absorption, tested in a laboratory. At the kiln, where no laboratory stands, the same bands are read by ear, by thumbnail, and by eye. I begin every purchase the same way, with two bricks lifted from the stack and struck together. A clear ring, almost metallic, and the stack stays in the conversation.

A dull thud, and the brick goes back on the pile and the seller's price for that stack quietly loses its audience. On my last trip to the bhatta, the seller quoted three grades at three prices in one breath, first, second, third, as though the words explained themselves.

This article exists because they do not, and because a first-time buyer hears them as praise and blame rather than as numbers. The bricks for wall calculator counts bricks without asking their class; this page is the missing half of the purchase, the part that decides what the counted bricks are worth.

The Tests I Run By Ear And Hand

The field tests take two minutes and a stack of bricks, and each one reads a property the laboratory measures formally. The ring test reads firing: a well-burnt brick is dense and homogeneous, and it rings; an underfired brick is porous and soft, and it thuds. The scratch test reads surface hardness: drag a fingernail, then a coin, across the face.

A sound face resists both; an underfired face powders and marks. The drop test reads brittleness and strength together: a good brick dropped flat from about a meter onto hard ground survives or breaks into large pieces, while a weak one shatters.

The eye reads the rest. Color should run an even cherry red through a broken section, not pale at the edges and black at the core. Shape should hold its edges and corners. A heap where every fifth brick fails one of these tests is priced as the class below its label, whatever the label says.

The kiln sells words: first, second, third. The stack in front of you sells evidence. Buy the evidence.

One more field test deserves its place, the soak. Weigh a dry brick, soak it for a day, weigh it again. The gain is its water absorption, the single number that predicts how a wall drinks rain and how mortar bonds to the face.

A buyer who runs the soak on three bricks from a stack knows more about that stack than an hour of negotiation reveals. I skipped it for years myself, buying from kilns I had watched season after season. A first-time buyer has no such history, and the soak is the history, compressed into a bucket and a scale.

The Same Classes, In The Standard's Language

IS 1077, the Bureau of Indian Standards specification for common burnt clay building bricks, sorts bricks into designated classes by compressive strength and caps the water absorption each class may show. The traditional first, second and third class names used at every kiln map loosely onto that system, and estimating practice attaches the following working figures to the three names. Formal project specifications cite the standard's own class designations, so treat this table as the buyer's translation, and the standard as the authority.

The three traditional classes, with their working figures:

I buy bricks by ear. The standard buys them by crushing strength. A good buyer learns both languages.

Notice what the table does to the kiln conversation. First class is not a compliment the seller pays his best stack; it is a floor of 10.5 N/mm² and a ceiling of 20 percent absorption, and a stack that fails the ring and scratch tests has failed to present evidence for either figure. Class also interacts with size: a grade quoted for a brick that runs short of the ordered dimensions is a smaller brick at the same price, and the size survey in Brick Sizes In Pakistan And India shows what that shortfall does to a wall count.

Two More Signs The Stack Gives Away

Efflorescence is the white salt bloom that appears on a brick face after wetting and drying, as salts inside the clay migrate outward. A light dusting on a sample is common and mostly a cosmetic matter; a heavy bloom across many bricks in the stack warns of high salt content, which later shows through plaster as pale patches that return every season.

Kilns rarely volunteer the test, and it costs a buyer one brick and two days: soak the brick, let it dry in the sun, and read the face. The standard treats efflorescence as a graded property with its own limits, one more case of the laboratory having a word for what the eye can already see.

The opposite failure also has a look. Overfired bricks come out of the kiln's hot heart dark, glassy, and often warped, their edges fused and their shape twisted. They are hard, sometimes harder than first class, and nearly useless in a wall line because a warped brick will not sit in a true course and drinks almost no mortar bond.

Sellers blend them into stacks as ballast. A buyer checking shape, brick by brick down a row, is checking for these as much as for the soft underfired pieces at the other end of the firing range. Grade, in the end, is a band with two edges: too little fire and too much fire both fall outside it.

Which Grade Goes Where

Placement follows load and weather. Load-bearing walls and walls that face the rain carry first class, because both strength and absorption are being spent there every season. Internal partitions, which carry little and stay dry, are the honest home of second class, and many boundary walls run second class between sound pillars.

Third class belongs to temporary work, filling, and garden edges, places where failure is an inconvenience rather than a repair. The downgrade that should never happen is silent: first class ordered, second class delivered, the difference pocketed in transit. The defense is the two-minute test routine at the truck, not at the kiln, because the truck is where the stack becomes yours.

Standing At The Kiln With Three Prices

The concrete use case is a buyer with a count in hand, say the 8,584 bricks from the boundary wall article in this series, facing three per-thousand prices and a seller in a hurry. The grade decision changes that bill by more than any negotiation over the last fifty rupees per thousand, and it changes the wall for decades.

Run the tests, match grade to placement wall by wall, and let third class leave the yard for someone else's garden path. Then protect the purchase on the road and at the stack: the ordering guide on Wastage And Breakage covers the rejects conversation to have before loading, which is the same conversation this article starts, finished at the point where money changes hands. A wall is bricks plus judgment. The count supplies the bricks; the class, checked in both languages, supplies the judgment.