Increasing numbers of social thinkers are writing today about how we are living in a materialistic world, suggesting consumption and depletion of resources. By gentle twist of words, we can also say that we are living in a material world, with maddening choice of materials. Selecting and shopping what we need is no more a simple task, but demands researching and rejecting among the options. The idea of selection would vary case by case, with eco-friendly construction having its own set of criteria. Over the decades, specific qualitative and quantitative standards have been evolved to judge and classify materials under the green category.
In principle, all the building materials come under 3 categories – natural, processed and manufactured. Mud, wood, stone, sand, slates, lime, bamboo, rattan, thatch and such others which we use mostly in their natural state with minimum re-sizing come under the natural category. Even today, these materials dominate the larger building stock of the world and are among the best choices towards a sustainable future. However, if they can meet the quantitative demand for materials in this ever expanding urbanization is a matter of debate. Also, while items like wood are renewable sources, few of them like stone are exhaustible. Much of contemporary architecture of today can not be achieved only by natural materials. Notwithstanding these counter positions, we may safely assume that using natural materials compliments our objectives of sustaining the Earth resources – an option with least energy consumption, minimum procurement wastage and negligible residual wastage.
The next category called processed materials suggests an altered state of the material, process itself ranging from the basic to the advanced. Village brick making with firewood alters the raw clay into burnt bricks permanently altering the characteristics of mud, hence can be called as processed material. So are products from iron ore, paints from vegetable dyes, pottery from clay and tying ropes from natural fibers. They consume some energy and produce some waste, but get customized for the intended use, hence become more efficient than being in the original state. Like the natural category, the processed items also lead to depletion of natural resources, hence judicious degree of processing and usage may balance their adverse effects.
The worst kind that leads to maximum resource consumption, waste generation and energy requirement are the third kind – manufactured materials. Excepting some raw materials used in the production process, much happens through chemicals and artificial means to bring a new material to the earth. The high ended industrial process not only demands skill, but also wide spread marketing to make the production financially profiting, a goal normally fulfilled by the market economy. The artificiality of the material ensures, the raw materials used never get to return to earth and regenerate. Popular items of today including steel, cement, glass, aluminum, plastics, construction chemicals, vitrified tiles, adhesives, insulation items and many more of them are flooding the building scene today.
No wonder, the green house gas emission from building industry has been on raise – a matter to be taken more deeply.
Materials for stairs have to meet multiple demands: be safe, uncluttered, non-slippery, durable, and easy to maintain.
Among the factors critical to good architectural design, appropriateness of materials could be rated as very important. How we design needs to be complimented by what we build with. In a steel staircase, the decision on support member is pre-determined, but the step or tread member could be a studied decision, based on the location of stairs and type of users. The only pre-condition appears to be that the step should be in a single piece.
Wood is not only the most traditional staircase material but also the most popular one found in different countries. Wooden steps are non-slippery, can be given desired degree of smoothness and ensure a feel good factor. Bolts and nuts make up good fixing detail, while nailing also can be employed in select places.
If a building has marble flooring, a matching look can be achieved by using marble for the steps as well. They appear rich and classy! The slabs can be placed within the angle frame, provided with rounded off or double-layered edges with rough finish at the nosing to reduce the danger of slippage. Marble tends to appear fresh where we keep walking upon, leaving the corners and sides with less usage with a brown patch over the years.
Natural stones like granite when locally available can make a style statement, matching with the floor or contrasting with it. It has a good colour blending with steel and comes in a single piece like wood or marble. Highly polished granite can be slippery, hence should be avoided. Alternate single piece stone slabs of kota, tandoor and such others can also be considered, if additional frame support can be provided to counter their tendency of cracking.
It’s glass too
Nowadays glass has joined the list of optional materials, possibly more for shops and galleries, where certain fancy looks stand to advantage. Elegant and long lasting, thick plate glass is a novel idea, strikingly different to all the traditional materials.
Railing materials have lesser options, with wood and steel being the two major choices. The top handrail has to be in good quality wood, for the comfort of hands and good grips. Balusters, as the support members are technically called, can also be in cast iron, but should be designed with the desired gap to make them child safe.
It is only in the lower part that the members need be closer, leaving a choice of design otherwise. Once the design of vertical support is sorted out, additional members like wood, glass or thin steel sections can be employed to provide good aesthetic appearance.
Unlike for normal flooring, where many materials fit, appropriate materials for stairs are limited. They need to meet multiple demands: be safe, uncluttered, non-slippery, durable, and easy to maintain.
Filler roofs are designed using the same principles as RCC, except for replacing part of the concrete with some alternative material.
Last week belonged to queries about filler roofs, following the preceding essay introducing the idea. No wonder there were so many questions about it, considering it is an exciting solution, though less heard of. While the regular RCC is widespread even in remote villages, it is surprising that filler roofs are hardly known around and have minimal visibility.
By the early 1980s, many roofs were cast with filler material in Kerala and later in Bangalore too. With nearly 30 years behind them, their durability has been repeatedly proven. Incidentally, when a commoner wonders if the roof is strong enough, what actually he enquires about is whether the roof will structurally perform well with load transfer, tension, compression, deflection and such technical matters. Since filler roofs are designed using the same principles as normal RCC, except for replacing part of the concrete by some alternative material, worries about strength can go unquestioned. It is the designing for tension load, hence the spacing of steel reinforcement that would differ as per the sizes of filler material.
No new problem
Behaviourally, the slab acts like any other slab, and as such does not pose any new problem not seen in regular RCC roof — be it with possibilities of water seepage or cracks! In either case, normal RCC or filler, such issues need to be attended to, should they appear unfortunately. Quality of construction at site is a pre-condition which can affect both the mainstream and the alternative practices, and as such should not be used only to degrade the alternative!
Availability of the hollow clay filler blocks could be an issue, to be explored by the potential user, but any local clay roof tile supplier could be of help. Alternatively, a variety of locally available materials could be inserted as filler, including stabilised sun dried mud bricks. When we place glass bottles or perforated jali blocks, we get skylight effect.
Cement blocks have already been experimented with, which then could be plastered and concealed. There are many filler roofs done with mud pots or bowls as filler material, where we get the looks of an artistic ceiling, at a lower cost.
While concreting, the filler blocks may move due to labour movement, which demands careful on site handling. Depending upon the room size, there could be savings in the steel cost; however the cost of block and increased labour would ensure our savings are spent! In large span roofs, where it is desired to avoid the beams, one may design a thicker slab, then introduce filler concept to save on concrete.
When the whole roof gets cast as clay filler slab, it’s possible that some family member may not like the red look at the bottom of the roof. Such people have the choice of getting the ceiling painted white, giving a designer false ceiling appearance, thanks to the fluted profile of the block!
Filler slabs do not demand greater technical skills or supervision than the normal slabs, and hence can be employed widely.
We are talking common sense. When we need to buy something, if it costs high, either we shop for a different item or reduce the quantity of purchase. In the case of roof, concrete is not replaceable on most occasions. So, the least we can do is to reduce the RCC quantity, which can be done by partly replacing concrete by any other economical, beneficial or attractive material. Since the roof thickness gets filled so, technically such roofs are termed as filler slabs.
Incidentally, even though all RCC roofs are a single monolith cast of concrete along with steel, the area between the steel reinforcements play no role in load transfer. Yet, we cast the roof in full because it cannot be cast with innumerable voids in between, considering the form work or the temporary supports that are required for casting the roof.
One solution popularised by Lauri Baker, the pioneer architect of cost effective architecture in India, was to place two numbers of low grade Mangalore roof tiles in between the steel rods. Once the centering is done, the filler material is placed and then the steel rods tied as per the required spacing. Since then, architects and engineers have placed everything possible under the sun, including bottles, computer key boards, cement blocks, mud pots and such others to achieve filler slabs. The criteria in selecting the material has largely been the cost and its looks.
Since the heat gain from the roof is the highest, if the filler slab could be done using hollow materials, we get multiple advantages – passive solar cooling where the voids reduce the heat transfer, lesser roof weight thanks to the hollowness, different looks when seen from the room below, reduced sound transmission between the floors thanks to the voids in between and reduction of steel consumption considering greater distance between them. Accordingly, nowadays a special block called hollow clay roof block, also called as maruthi block or filler block, has gained popularity. These are manufactured by clay brick and tile manufacturers, mainly in Kerala and Karnataka.
Once the roof centering is complete, it is levelled by a layer of stabilised mud or very weak cement mortar. First the roof blocks are placed end to end as per the structural engineers design, placing them closely and compactly. The minor gaps in between are sealed with the same lean mortar to reduce curing water flowing down after the roof casting. These blocks come with specific spaces to run the steel rods, in both the directions as required by room spans. A layer of thin steel rods is placed on top, electric conduits are tied and the roof is concreted as usual.
Following the stipulated 21 days of curing and de-shuttering, the construction proceeds just like any other roof. Filler slabs do not demand greater technical skills or supervision than the normal slabs, hence can be employed widely
They are quite strong and also add character to a building
Simple: The construction process with soil cement blocks is like building with any other block, except taking care of joints and corners
With reference to mud buildings, though rammed earth has a greater history behind it, building a stabilised mud block (SMB) or soil cement block (SCB) wall is much easier and convincing to a new client. Commonly, mud blocks measure 9”x9”x6” with minor size variations, edge profile and cornice decoration options, as may be required for the project.
The soil is prepared the same way as for ramming, but here it is packed into the molds within a small machine. The machine comes with a pressing lid, operated by two workers throwing their weight on it, so the soil gets adequately compacted. After compacting, the fresh blocks are lifted out of the machine and kept in the open outside for drying under the sun. All this can be managed within a 60×40 site or even smaller sites if the road sides can be used.
All the three major institutes, viz. ASTRA, Auroville and DA, have developed their own versions of the block making/pressing machine, with the ASTRA model being popular in Bangalore. It is advisable to have three labourers as a team to start making blocks few weeks before the wall construction, get the blocks sun dried and stock up at site. Ideally, the soil dug up from the site itself should be used for blocks, to save on transporting mud from outside.
There are testing labs such as Mrinmayee which can study the sample soil to give advice about the water content and quantity of cement and stone quarry dust to be added to stabilise the soil. However, in case the soil is unfit for blocks or it is in short supply, blocks may have to be ordered from outside.
The construction process is like building with any other block, except for care for joints and corners. Unlike what many people fear about, the SMB wall is not a weaker option! While a normal brick can be cut by the mason using his ‘karni,’ here we need a cutting machine. Even electrical grooves cannot be done by a small chisel and hammer, but once again demand machines. No water can seep through the block, as such external pointing is important only to ensure water-proof joints. The joints with stabilised mud mortar can take any number of nails, a routine household requirement. Of course the joint lines, both horizontal and vertical, are visible in the building, adding a character to it.
Alternately, the wall can be mud-plastered if an even surface without joint break is desirable. It can also be painted with any colour, if the mud looks need to changed. It is interesting to note that a mud building offers the option to completely conceal the mud looks or celebrate the earthy looks, once again scoring over other choices. However, we need not highlight the intentions of using mud construction and what option most owners choose!
Applying traditional mud-based construction methods in modern urban contexts
We owe the early studies about mud architecture to CRATerre at Grenoble, France, the ASTRA group at Indian Institute of Science, Bangalore, Development Alternates at Delhi and Auroville at Pondicherry. The work at ASTRA during the 70s directly focused on how to apply the traditional mud-based construction methods for modern urban contexts. Very soon, they realised that mud cannot be used directly in its raw state. The process of stabilisation does the magic and the powdery soil becomes hard.
About this process, I tried to write on my own, but nothing came as good as what K.S. Jagadish, among the early researchers at ASTRA, IISc., wrote in his book ‘Building with stabilised mud’ (I.K. International Publishing, 2007). To quote him, “Since mud is the most widely distributed resource for building construction, it is useful to explore ways of ‘stabilising mud’ without employing energy-intensive techniques like brick burning. Stabilised mud may now be defined as mud which does not soften due to the action of water, by the use of a small quantity of a binding agent. Cement, lime, cement and lime, lime and pozzolona, bitumen and organic binders are some of the typical stabilisers which can be used.
Criterion:The performance of a soil-based building block depends to a large extent on its density
The performance of a soil-based building block depends to a considerable extent on its density. Low-density blocks are rather porous and will not have good strength. It is hence necessary to densify soil while making a stabilised block besides adding the stabiliser. For this purpose, the soil has to be subjected to adequate pressure at suitable moisture content. This process is known as ‘compaction’. The compaction can be done inside a machine mould to produce a standard-sized ‘mud block’. Alternately, the soil can be directly compacted in a wall using a moveable mould in what is known as ‘rammed earth’ construction.’
Though today in Bangalore, we build more with compressed blocks, the rammed earth practice pre-dates it as a vernacular method. In recent times, Bangalore-based Mrinmayee centre has improvised the ramming technology further, attempting to popularise it.
It’s a simple mechanism with two side plates anchored together within which soil is poured and a flat wide-based hammer is used to manually compress it. All the components are removed and re-fixed again for the next section of the wall.
Only one horizontal course up to 60 cm can be built in one day. As per the plan, the openings can be left for windows, grooves can be cut for electrical wiring or nails can be hit for hanging art works.
There of course are few precautions to be followed, but at the end, one can get a rammed earth house which is no less beautiful or strong compared to a conventional one. May be, the mud house could be better!
In more ways than one, stone is among the most complete and eco-friendly construction materials
There are millions of buildings all over the world built completely with stone, right from foundation and walls to floors, stairs, columns, beams, roofs and parapets. But for re-sizing, constructed stone is the same as what nature has provided us, with no processing at all, unlike mud and wood which get partially altered by us.
Staying cool in summer and warmer in winter, it responds to local climate very meaningfully. After the life of the building, stone returns to earth equally easily.
India is a fortunate country, in having abundant supply of stone as a possible building material, both in variety and quantity. Eastern Maharashtra may be rich in basalt, Rajasthan is full of marble, while Kerala has extensive laterite deposits.
The pink sand stone of Jaipur region is synonymous with the pink city itself. Local inhabitants have discovered what the nature has in store for them and accordingly, each region has historically developed the art of building with stone.
Rocks and boulders
Bangalore region sits on the Deccan plateau, with both sheet rock and boulders. As such, granite size stones, boulders, slabs, hard aggregates and other variants are commonly available here.
Depletion of natural reserves is a major cause of concern today, with excess stone quarrying denuding the large rocky countryside. As such, while we may credit stone as a complete eco solution, it will have to be used judiciously in future.
There are better alternatives for columns, beams and roofs, where we can spare stone, leaving it mainly for foundations and walls. We often come across walls with both side stone left exposed with thickness up to 15 inches, while stone composite walls with 12” thickness are more popular. Much thinner walls at only 8” is possible with slabs, but they cost twice the regular ones due to cutting and dressing.
The criteria of cost resulted in many houses with random rubble walls, an 18” thick wall with irregular stones and no straight jointing. They appear very natural, however demand an experienced mason to build them and waterproof the joints.
What most of us see as stone wall, in recent times, could actually be normal brick wall finished with a large slab or small cut stone pieces, known as cladding. It ensures speed and even surface, can be applied for lintel or RCC edges to hide the concrete look and create different patterns.
Cost is a major concern here, also the aesthetics. Such walls often lack the real stone look, due to the slab face and tend to appear decorative.
Methods of building with stone could be different, but the basic precautions to be taken are similar. Learning about these principles itself can be an exciting journey into architecture!
Every other builder or designer claims that he can work with all materials, when actually, the facts are otherwise
Working with a material is not as easy as it appears. We need to know the characteristics, how best to use it, common problems and possible mistakes that we may commit. It’s like a chess champion knowing the opening game, a cook negotiating with a vegetable or a potter working with the type of clay.
The master works with ease, where the novice still struggles. Unfortunately, in the construction field, everyone poses as a master with every second builder or designer claiming they can work with all materials! In all of my 16 years of consultancy, I am yet to meet a contractor claiming inability to build with stone, even when they accept not having ever built a stone wall earlier.
This long introduction became necessary, in the light of occasional discussions the professionals have been having about disseminating information in public.
We still remember what happened to the image of soil cement blocks during its early years, when it was made and built without proper care.
Often, we see exposed brick walls so badly done, and I want to say, “Someone please plaster it off immediately!” This happens mainly when a helper is assigned to build a wall and a brick layer becomes a stone mason overnight.
All material technologies demand certain lead time to understand how to use them, before a builder can start with them.
Real picture: Architects, masons and others need some time to understand material technologies before starting the building work
As such, while writing about construction is useful, it may also lead to creating overconfidence among the practitioners, who may try their hand on field without adequate preparation.
Composite walls that we discussed last week face this danger more than any other wall type. Most masons get no chance of visiting a building under construction with the said technology, so end up re-discovering the wheel of learning all over again, making the same old mistakes in the process and killing the great new idea for ever. Unfortunately, while people have gained expertise during their practice, no major attempts have happened to record their knowledge as a code of practice or builders notes to help others learn.
Even if we have such texts, it can only compliment the hands-on work. Design, however cerebral it may be, finally ends up as a visible and tangible act.
Architects and owners observing a finished building during day light, builders learning about the experience of others and masons actually building sample walls under expert supervision are all among the mandatory preparations a project should undergo before embarking on the alternative path.
Working with a material is not as difficult as it may appear, if we can prepare well.
People working with clay crafts can tell us the finishing like glazing and pattern-making makes the pottery better, but costly as well. It is true in building construction too where the finishing costs are double of basic superstructure, hence our emphasis on leaving the material exposed.
In a composite wall, the outer and inner layers need to be tied to each other by a single stone going through the thickness of wall or a small piece of reinforcement rod or there should be adequate randomness in the wall core such that two layers do not fall apart. The course height would vary between stone and bricks, so only occasionally both would be at same level, which is acceptable.
However, when they reach lintel or roof bottom, both the materials need to reach together. It demands pre-checking the course height and the mortar joint thickness, adjusting it to match with levels as needed.
Periodic checking of levels with water tube levels is a simple measure to ensure quality of finish. To maintain uniform joint thickness, a piece of wood of desired thickness could be used as a standard reference.
If both sides are to be exposed, the electric conduit pipe should be laid within the wall during construction itself!
Composite walls in stone and bricks have all the potential we need, but one precaution: once done, there is no changing; hence the first time itself, we need to get it right.
Soil was processed to get building mud, dried under sun resulting in un-burnt mud blocks, fired up to get burnt bricks, then evolved into better types like chamber and wire-cut bricks. India exhibits, historically and otherwise, a wide range of brick structures.
In composite masonry walls, needless to say, bricks are among the most commonly used. The outside demands burnt clay blocks or wire cut bricks with high surface density and resistance to wear and tear, while the inside could be the normal table-molded bricks suited for plastered finish.
Granite stone, either as size stones or as slabs, is popular in composite walls along with bricks in Bangalore contexts, both being local materials. Just working with stone and bricks, often keeping stone outside for elevation and then reversing at other places, making it the internal wall, is actually fun! The resulting external and internal patterning can be so interesting; no additional efforts would be called for to create the building elevation.
Leaving material exposed
Why are we repeatedly emphasising on leaving the material exposed? It is not only to reduce heat gain, but equally well to reduce construction and maintenance costs.
People working with textiles can tell how cheap the basic cloth is and how finishing it demands money. Hence, using khadi or simple kora cloth is always an economical solution.
Let us at least feel happy that composite walls have been rediscovered and are gaining popularity
Attractive: Indoor and outdoor walls can have different textures
Everything in nature requires protective external cover, just like our own building walls. The difference is simple – nature has designed millions of plant and animal skins while we have only a handful of wall solutions.
Let us look at a dry coconut, complete with its inner shell and thick outer protective layer. The outer skin is so hard it requires sharp tools to peel it off. After we de-husk it, we see the inside being soft and fibrous, in total contrast to the outside finish and surface. Let us peel a banana, scrape a cucumber, study animal skins, or cut a pumpkin.
The story is the same, with the outside skin designed for harsh external environment for survival, while the internal surface is finished simpler, relating more to the soft pulpy contents inside. There is no logic that demands both to be same. Instead, the inside and outside being different is the logic.
Now let us look at our own building walls. Nearly all that we build today has a wall plastered and painted both sides, almost similar but for the type of paint. Incidentally, architecture from the past exhibited at least some variety. The grand palaces of Rajasthan, all built with stones outside, did not have stones visible inside. They were smooth finished, with stucco, niches, mirror, paintings or anything else that the room wanted. The rural houses in northern Karnataka have walls in stone, built with minimum masonry joints, but inside finished with mud plastering. Laterite walls left exposed are a common scene in the vernacular architecture of the west coast, which are rendered with lime mortar inside. Fort walls were constructed with stone on both sides.
Off with colonial ideas
With all this background, why have we forgotten the lessons from the past? We can cite many of them including the imposition of uniform ideas from the colonial powers. Leaving it all aside, today, we can feel happy that composite walls have been rediscovered and are gaining popularity.
It is building a wall with one type of material or finish outside and another type inside, both decided as per the needs of respective contexts.
Over the last 15 years, our firm has explored numerous combinations of singular or composite walls with soil cement blocks, granite size stone, normal table molded bricks with plastering, wire cut exposed bricks, hollow clay blocks, Besser cement blocks, hollow jail or perforated walls, stone slab walls, rat trap bond walls and such others.
Right decision needed
Each material and construction type needs to be judiciously finalised, based upon location, cost, heat gain, elevation aesthetics, maintenance and the desired final finish.