Clay jally for walls: light, air and shade

What a clay jally does on a wall

A clay jally is a wall with holes in a pattern. That sounds simple, but the pattern does three separate jobs, and knowing which one you need most helps you choose a design.

It shades

The solid ribs of the jali block direct sun. On a west wall in June, that is the difference between a room that bakes all afternoon and one that gets a pattern of small light patches instead of a slab of sun. The preview above shows how those patches move and stretch through the day.

Low sun (early morning and late afternoon) comes in almost flat, so light patches reach far into the room. High sun at midday falls steeply and the patches stay close to the wall. In north India the west and south walls take the most heat, so a jali there does the most work.

It lets air through

Because the wall is open, air keeps moving even when the windows behind it are shaded. A jali high on a wall, or in a stair tower, lets warm air out at the top. That is why older houses in the region used perforated brick on stairwells and kitchen yards.

It screens the view

From outside in daylight, a jali reads as a patterned wall; it is hard to see into the darker room behind. From inside, you can see out through the openings. At night, with lights on inside, this reverses, so plan curtains or blinds behind a jali if a bedroom faces the street.

Choosing a clay jally design by job

• Most light and air: Opal Jali and Petal Jali, or the white Design 8 ring.
• Balanced: Flower Jali and Square Jali. Square throws neat rectangles of light, Flower throws petals.
• Most privacy and rain cover: Camp Jali. The hooded face blocks a straight view and sheds rain.
• Changing light through the day: breeze block Design 4. Its deep funnel lets light in at an angle, so the patch moves a lot as the sun moves.

Rain, monsoon and the clay jally

An open lattice lets in some rain when the wind drives it sideways. Three things help: a chajja or roof overhang above the jali, a sloped coping on top of a free-standing jali wall, and a floor inside that can take a little water near the wall. On walls facing the monsoon wind, the Camp Jali is the safer pick.

Clay jally in cold places

In the hills, think about where a draught is welcome. Stair towers, parking floors, utility rooms and verandah sides are good spots. Living rooms and bedrooms usually are not. Fired clay takes in a little water, and repeated freezing can damage a block that stays wet, so keep jali under an overhang at higher altitudes.

Laying and looking after it

A clay jally wall is laid like brickwork, in cement and sand mortar, usually in stack bond so the pattern stays continuous. It is a screen, so it goes inside a frame and carries no load. Read the full method in how to lay a terracotta jali wall, and count blocks with the jali brick calculator.

Cleaning is water and a soft brush. If you want extra protection outdoors, a clear breathable sealer for terracotta can go on after the mortar cures.