Bricks, eco-friendly paint, glass partitions…



Architect Navneet Malhotra is a perpetual student. He loves to break myths and unmask the true cause for bad work by constantly sharing experience… “Path to gaining knowledge is through sharing,” is his motto.


I would like to use fly ash bricks in the construction of our house as I am keen on using environment-friendly materials. I am told these bricks less sturdy, absorb more water and have a weaker grip with the mortar and plaster than conventional red bricks.

I have a couple of questions regarding these bricks? Firstly, do they pose problems when chasing for electrical and plumbing pipes? Secondly, is it true that they are heavier than conventional bricks and therefore require a heavier foundation to support them? And finally, does their colour bleed into the surface?
Sandeep Anand Goyle, Faridabad

I am glad to know you are considering using fly ash bricks to construct your house. These bricks are made by adding 6 per cent to 9 per cent cement to the finest grade of fly ash — which, as you may be aware, is waste generated by coal-based power plants. These bricks are beneficial to the environment in several ways: they prevent cultivable top soil from being used for non-biodegradable ‘bricks’; save timber and coal used to bake these bricks and consequently reduce carbon emission; and protect the land from being covered in fly ash, which has very little nutrients.

If made well, fly ash bricks are denser and stronger than conventional bricks. They have been found to be more consistent in size and shape, and their body more evenly made with smoother surfaces. Being denser, they absorb less water than conventional bricks, and, no, their grey colour does not bleed into the plaster of the wall.

Fly ash bricks have not become as popular as they should be because a few manufacturers reduced the recommended percentage of cement, making the product weak and brittle. I also stopped using these bricks when I saw them crumble under the hammers and chisels of plumbers and electricians. But all manufacturers are not the same. You will find fly ash bricks that are much stronger than conventional bricks in the market. They are marginally heavy, about 2,000 kg/m3 to 2,050 kg/m3 as opposed to 1,800 kg/m3 to 1,900 kg/m3 of conventional red bricks. This difference in weight will have negligible impact on a low-height (under 20 m) residential structure.

One simple (but not accurate) method of checking the strength of the bricks is to hold one in each hand and bang them together. (Make sure your fingers are safe!). If either of the bricks breaks, don’t use them. Another (safer) test, albeit with even lesser accuracy, is to drop the brick onto a hard surface from shoulder-height.

There are a few precautions you’ll need to take while working with fly ash bricks. Some of them don’t have the frog (shallow depression) seen on one of the large faces of a traditional brick. Manufacturers often put their initials in this frog to make them easily distinguishable. A brick is placed frog up to ensure that the wet mortar that sits in it, ‘grips’ the surrounding bricks.

The absence of the frog and their smooth surface necessitates special precautions while working with fly ash bricks. Make sure they are wet when being used for making walls or when plastering. The thickness of the mortar (masala) between the bricks should not be less than 12 mm. Masons often put a generous layer of mortar on the horizontal surface, but skip a couple of vertical joints in each row to save cost, time and improve productivity. Do not accept this.

Even though a good fly ash brick will have no problem with chasing or cutting of shallow trenches for pipes, it still helps to have a chase-cutting machine handy. Alternatively, you could use a regular hand-held stone-cutting machine to reduce the impact of a chisel and save time. Be sure to use a double layer of chicken wire mesh on all masonry-concrete (column-wall, roof-wall and beam-wall) junctions.

I have been looking for eco-friendly, low VOC /low toxicity type of paints. During my enquiries with paint companies, I was given to understand that water-based paints, enamel, and lustre are ‘green’. Is this correct? I just want to ensure a healthy internal environment, and was therefore trying to avoid toxic paints on walls, woodwork, etc.
Nitin Kichlu, Mumbai

There are two basic categories of decorative paint: water-based and solvent-based. After conducting a little research by calling a few vendors and friends in the paint manufacturing business, I realized that the ‘lead free‘ and ’non chrome‘ paint is a toxicity-free green product. So to think that a water-based paint such as oil-bound distemper is free of toxic materials, won’t be correct. This information, unfortunately, is not highlighted on the paint container. Manufacturers of industrial paints, as per my friend Divey Ahuja who is from this segment, have to compulsorily mention all the ingredients used in making the paint on the container. As this is not true for ‘domestic’ paints, most manufacturers fail to mention the lead or chrome content on the packaging.

As per the LEED rating system, VOC or volatile organic compounds must be less than 50 g/lt for a flat, interior-grade paint and less that 150 g/lt for a non–flat, interior-grade paint for it to be considered green. Unfortunately, wood polish, varnish and lacquer have even higher levels of VOCs.

Karan Kapoor of Asian Paints informs me that water-based paints generally have less VOCs as compared to solvent-based paints. This corroborates your finding as well. The operative word is ‘lower’, which, you’ll agree, is not the same as ‘completely free’. Therefore, if you are still looking for paint that is completely natural and free of VOCs and toxins in the scenario, consider a ‘traditional’ one like limewash and whitewash, or imported chalk paint. But, limewash will probably not give you the desired finish… so I guess we will have to live with lower paint toxicity till the manufacturing industry wakes up to the present needs of the customer.

Our interior contractor had promised to hand over the office in 30 days, but now, after 20 days, he says the moisture in the air is delaying the drying of the plaster of paris on the walls, which is why he cannot start with the painting. Is there any truth in his statement? Can we accelerate the drying in any way, perhaps by putting a couple of room heaters in front of the wall?

One more issue I need to resolve involves glass partitions. He insists that the flooring will have to be laid out before he can order fixed glass partitions for the office and its entrance door.
Rohit Nandwani, New Delhi

With the rains and the high humidity, it is not surprising to hear that the plaster is not drying as fast as you’d like it to. Using heaters will definitely expedite the process, but don’t place them too close to the wall, facing a single spot. This will only cause water to evaporate from that small section, leaving the surrounding plaster wet. This increases the chances of cracks due to differential shrinkage. Placing the heater at least 5 feet to 6 feet away from the wall will result in more evenly distributed heat.

Ideally, the entire room should be heated. You could have asked your contractor to experiment with solutions such as dry wall cladding. The price of such systems (gypsum board or sun board) will be about Rs 60/sq ft while the POP plastering will cost you about Rs 15/sq ft to Rs 20/sq ft. This may sound like an expensive solution at the outset, but think of the additional rental costs and loss of business… it may make your choice easier!

Coming to the second part of your problem, most full-height glass partitions and doors (with or without frames) need to be of at least 12-mm-thick toughened glass. Raw glass sheets have to be dressed, cut and sized before being sent out for toughening. And once toughened, they can’t be altered at all.

So if the floor has not been laid yet, it will difficult for your contractor to take the exact dimensions of the glass partition. Solution? You could start by placing level-markers at different locations to match the finished floor level of the office. Now start by laying one row of tile under each location where a partition is proposed. Cut cheap, thin plywood to the exact size of the glass panel. These stencils can be used as a ‘format’ to cut the glass to size before it is sent for toughening. Later, they will come in handy for finishing the false ceiling, floors or walls.

In case you are short on time and don’t mind taking extreme measures, you could install the panels in critical locations — such as the main door. As long as the office is secure and air conditioning effective, you can start work. Internal partitions can always be installed later.

I have a set of old carved wooden chairs that I wanted to re-upholster. The new furniture that we’ve ordered is straight-lined, so the chairs will be an absolute misfit. My husband would rather let them go, but I am sentimentally attached to them. What do you suggest?
Kiran Sharma, New Delhi

You could easily modify these chairs to match the new look. You can add or remove arms, or alter their backs and even the silhouette. If the chairs are as sturdy as you say, they’ll outlast most of your new furniture. My advice is to tweak the old, and save time and money.