Among the recurring themes of Green Sense essays, one aspect that many readers get puzzled by is the periodic emphasis on leaving the walls un-plastered. A look by architect SATHYA PRAKASH VARANASHI

It may not be possible to leave the walls un-plastered all the time, but exposing the masonry whenever possible reaps many benefits.

This wisdom comes from observing how the rural buildings in many parts of India have lasted for decades and centuries, with stone or brick exposed. The material does not deteriorate by itself, unless faced with heavy rain, sun and wind, which were in those days protected by deep overhangs and verandahs. Water, the commonly suspected culprit in letting a building decay, does not seep through the masonry itself, but primarily through the joints. Traditional structures built with thick walls minimised this possibility, the thickness itself being a deterrent to the movement of water. Also, the more commonly used lime mortar would get stronger against water permeability over age, ensuring buildings lasted long without much maintenance.

Today, with thinner walls, we need to solve these challenges differently. In case of heavy rainfall areas, the mortar used to build the wall could be completely mixed with water-proof admixtures, such that the joint beds resist water penetration throughout their depth.

Even if the wall is only 8” thick, such an integrated water-proof mortar does the magic. Alternatively, the mortar could be the normal one, with the mixed mortar batch used only for finishing the joints.

Water-proof powder

A rich mix of 1:2 mortar with the water-proof powder mixed as specified by the manufacturer, is pressed into the joint with a special narrow ‘karni’ with good pressure from the hands to form an impervious high density surface on the face of the joint. This procedure is termed as pointing, done primarily to water proof the joint and also of course to make the joints appear neat.

Accordingly, pointing could be done with few optional finish – finish only the groove; touch upon the broken edges of the masonry; surface finish the face of the masonry along with the joints and such others.

Groove pointing suits exposed walls the best; however the expert team may decide the type of pointing based on case by case.

All kinds of pointing for the joints demand skilled workmanship, as such cannot be left to some team at site casually. In heavy rainfall areas, water-proof coating like shylax or other chemicals have been applied, to protect the wall and joints together. Such full wall application should be minimised, for they tend to show off by creating different kinds of surface shine.

There have been long standing sentiments against exposed walls, mainly rooted around the dampness seen in such walls.

The solution to the said problems are simple. It is only a matter of following the proper code of practice, the workers being sincere to their job and not compromising on the material quality.