Exposed brick and jaali facades leak or stain when the brick absorbs too much water, the joints are loose, or salts travel to the face. Specify bricks to IS 1077 with low absorption and efflorescence ratings, shelter the wall with eaves and a damp-proof course, use a cavity where exposure is severe, and do not rely on a sealer alone.
What is a jaali, and what is an exposed brick facade?
A jaali is a perforated screen, in stone, brick, concrete or metal, that filters light and air and gives privacy. An exposed brick facade leaves the brickwork as the finished face, without plaster or paint. Both are traditional in India and have returned in contemporary design. The post on contemporary Indian house design places them among six local moves, and this post is about how to detail them so they last.
The same walls face Kolkata’s monsoon. The issue is water: where it enters, where it goes and what it carries with it.
Why do exposed brick walls leak and stain?
Because brick and mortar are porous, and because water carries salts. IS 2212:1991, the Bureau of Indian Standards code of practice for brickwork, says unrendered walls permit more water to pass through than rendered walls, and so should not be relied on to give protection from rain except under sheltered or moderate conditions. It says a cavity wall will provide a perfect barrier to rain penetration. In Kolkata’s monsoon the weight of the argument falls on shelter, good bricks and tight joints, and on a cavity for the worst-exposed walls.
Staining has a second cause. The Brick Industry Association, a US body, says efflorescence needs three things to coexist: soluble salts within or in contact with the brickwork, water, and a path with a driving force that moves the water to the surface. The salts often come from the mortar, the backing, the soil or the trim, and not only from the brick. IS 2212 adds that soluble sulphates in bricks can react with cement in the mortar, causing expansion and cracking under repeated wetting and drying.
How should exposed brick be specified?
Name the standard, the class and the limits in the specification, and ask for the test reports. The checklist below is built from the Indian Standards.
- Class and strength. IS 1077:1992 gives eleven classes by average compressive strength, from 3.5 to 35 N/mm2. For an exposed face use a higher class.
- Water absorption. The standard limits it to 20% by weight up to class 12.5 and 15% for higher classes, after 24 hours’ immersion under IS 3495 Part 2. A brick that absorbs 20% can still comply, so for a visible face ask for a lower figure than the limit.
- Efflorescence rating. The standard limits it to moderate up to class 12.5 and to slight for higher classes. IS 3495 Part 3 rates it nil, slight, moderate, heavy or serious by the share of the exposed face covered, and treats slight as not more than 10%.
- Joints. Specify the mortar mix, the joint profile and the pointing. IS 2212 describes raked joints for later plaster and pointing styles such as flush, weathered, tucked and ruled. A joint that sheds water is better than a flat one that holds it.
- Bricks from one batch. Order the whole facade’s brick together, since colour and absorption vary between kilns.
- A sample panel. Build a panel on site, approve it, and keep it as the standard.
The studio’s visualisation for the Lauhati nursing college shows banded brick running between stone piers, with dark vertical fins that order the long facades and shade the windows. The project is ongoing and shown in visualisation, so it is a design, not a built wall. See the Lauhati nursing college.
How do you detail the wall so it stays dry?
Shed the water before it reaches the brick, and give any water that gets in a way out.
- Eaves and drip. A projecting slab edge, sill or coping keeps rain off the upper wall. Add a drip groove under projecting edges.
- A damp-proof course at the plinth, so water in the ground does not rise into the wall. The post on wall dampness in Kolkata explains how one works and how it fails.
- A cavity or a rat-trap bond. BMTPC says rat-trap bond, popularised by Laurie Baker, leaves a cavity behind each facer, and that where the stretcher face is left exposed the inner surface is protected from damp. The studio found no rain-penetration test of exposed rat-trap walls, so do not treat it as a guarantee.
- Flashings and weep holes at the tops of walls and over openings, so water that enters can drain.
- Movement joints. Long walls need them, and the sealant must be matched to the joint.
The post on rat-trap bond walls covers that wall type in more detail.
How should a jaali be specified?
Decide what it is for, and make the opening behind it work. A jaali has three jobs: filter sun, give privacy and let air through. The 2025 Megaron study by Bay-Sahin and Shah, which simulated a conceptual building in Kilis, Türkiye, found that jaali lowered temperatures by up to 2 degrees C in the cooling season, and that open windows were crucial. That is a hot-dry climate, so it is a guide to the mechanism and not a number for Kolkata.
Specify these points:
- The module and the opening ratio. A tighter pattern gives more privacy and less air.
- The material. Brick and terracotta suit humid air. Metal needs a coating that survives rain. Concrete needs cover to its reinforcement.
- Support. A jaali carries its own weight and wind load, so show the fixing and the frame.
- Cleaning. A fine jaali collects dust, leaves and nests, and needs to be reachable.
- The window behind it. It must open, or the screen does little for ventilation.
The studio’s built examples are the terracotta jaali ceiling in the Muchipara apartment, and at Hotel Nirvana in Bongaigaon, a wall pierced with scattered square windows that lets light into the rooms and corridors behind while keeping the front calm. The Hotel Nirvana page has the project facts. The post on Hotel Nirvana’s terracotta facade tells the project story.
Do sealers help?
Only as one measure among several. The Brick Industry Association says coatings are not recommended as the sole treatment to control efflorescence. IS 2212 treats rendering or a cavity, not a coating, as the remedy for rain penetration. The sealer advice the studio found was from manufacturers, so it is marketing, not independent guidance. If you use one, ask for the technical data sheet, test it on a sample panel and check that it keeps the wall able to dry.
What should you do next?
If you are planning a facade in brick or a jaali screen, the studio’s architecture service covers the elevation, the specification and the detail drawings. The contact page has the studio’s phone, email and form.
