Monthly Archives: June 2013
Designing parapet and compound walls attractively, balancing aesthetics and cost, is an architectural challenge
All of us are aware about the importance of a picture frame. Edging a picture on all the four sides, be it a photograph or artistic painting, the frame can be neutral, thus highlighting the picture. Alternatively, the frame may also adorn an antique wood look, sleek modern touch or thin line minimalism. These options are important in the process they compliment the picture.
Likewise, a building also gets framed by the front compound wall and the top-most parapet wall. The compound wall is the nearest element to the observer and the terrace parapet wall is the farthest one; between the two sits the elevation of the building, as such framing it. The idea of elevation, formed majorly by wall finish, proportions of opening, window types and such others seems to begin with the compound and apparently stops at the parapet, connoting the end of the building.
Despite such a major role for these two, we notice most buildings either have non-descript ordinary walls or a design repeated from some other context that appears unfit in the given situation, simply suggesting that the two walls have not been given their due creative credits. The compound and parapet may have more of aesthetic appeal than ecological perspectives, yet can be designed more sensitively from varied parameters such as cost, culture and context.
Considering the fact that compound and parapet are comparable to being the frame of the building, it is better to develop them upon the same design style. Similar looking walls look better than dissimilar ones, the latter appearing visually disconnected from each other and the building too. Specificities like required height, other elements like gates, voids within, pattern of wall top, option for planter boxes and such others ensure the two walls are not exactly the same, but can look similar.
In an eco-friendly architecture with un-plastered walls, try exposing the materials in these also, just like in the building, to get all the benefits of such walls. Simple solid walls could be cheaper, but most often neither highlight the elevation nor compliment it. Alternately, it is not worth designing a costly wall either. As such, designing parapet and compound walls in attractive and creative modes, balancing aesthetics and cost, is an architectural challenge.
Neither the parapet nor the compound wall carries any load, and privacy across the walls is not a criteria. So, these walls can be thinner than the actual building walls to save money; they can take small openings within to reduce the material usage; technically do not need any plastering and painting; the top line need not always be a horizontal straight line, but can take stepped patterns, and varied material options can be explored in designing these walls, often using more than one material in designer fashion. It is important to realise that they are not separate from the building elevation, but are part of it.
- Most buildings either have non-descript ordinary walls or a design repeated from some other context that appears unfit in the given situation
- Compound and parapet walls can be thinner than the actual building walls to save money and can have small openings to reduce material usage
The common queries about rainwater harvesting are more to do with its logic, especially the way common people perceive it. Why store water when it is raining outside? What if we have to order tanker water in summer despite doing rainwater harvesting? These are not aimed at dismissing the idea of using rainwater, but trying to hint at the possible limitations of water harvesting. Of course the answers to such queries are simple – much depends upon the way we use the stored water.
Using the rainwater during the monsoon reduces our dependency on the public water, treated and moved from far-off places, besides saving on our bills. As the rainy season ends, we should not use our stock of water, but save it till the time public supply starts to dwindle. By pumping up limited quantity every time the overhead tank goes dry, we can manage this stock for many weeks.
The Rajasthan way
There is a better alternative for those who can afford upfront investment and seek long-term water supply. Rajasthan is known for a concept called ‘tanka’, a large-capacity tank fully underground that collects rainwater and stores it. Applying this idea for today, there can be such tankas upwards of 20,000 litres capacity dug within the site. The main criteria are to ensure total darkness in this chamber, which enables water to stay fresh for long, and ensure it gets full by the time rains stop so that we get maximum storage.
Tankas are better fitted with mono-block pump with only a suction pipe getting into the tank, though submersible ones can also be used. However pure the rainwater is, there will be certain dissolved particles and traces of dust from the terrace that may escape the first flush that will settle down at the bottom.
Since there is no outlet at the bottom to clean, manual cleaning is necessary when the tanka has no water. To get in for cleaning, keep a small, i.e. less than 3’x 3’ trap door either in the side or on top of the tanka as per site condition.
In many places, especially house sites, the setback or garden spaces left around the house may not be enough for the tanka or we may not like to lose such areas for an RCC roof. In such cases, the tanka can be dug under the house and fitted within the house walls, as if it is a basement space. The walls need to be structurally designed as retaining walls, to take care of soil and water pressures. Not only we save space, but also get to save water.
Investing on a tanka is worthwhile across many years, and may not suit budget buildings. However, those planning for a rainwater sump can plan to extend the water storage capacity. With water today, the advice is simple – save more, store more and use less.
Unless we speed up our efforts towards water conservation and judicious consumption, the problem is bound to increase.
It is good to see rain water being saved and used in urban areas on a wider scale nowadays and the resistance towards its storage reducing in the rural areas. Also, in many urban areas, rainwater harvesting is compulsory. However, this simple solution to the water crisis does not appear to have kept pace with the increasing crisis. As such unless we speed up our efforts towards water conservation and judicious consumption, the problem is bound to increase.
Among the basic causes, many city residents are apprehensive and hesitate to use it for daily needs like cooking or bathing, despite all that has been covered in the media about water harvesting as a larger proposal.
Many people collect the raw water from roof tops and let it percolate within their site. Some store the treated water in a sump for gardening, car wash and such allied purposes. Ideally we should be collecting the filtered water in a sump, pump it up to the terrace water tank otherwise done for public water supply and use it for all building and living needs. Only then we are saving the rain water to supplement daily needs. The rain water is perfectly suited for such total use.
There are a few systems to filter the water such as pop-up filters fitted within the pipes; gravel, sand and charcoal beds; and cloth filters. Let the water be filtered by the chosen system and flow into the storage sump which can be placed next to the public water sump.
Many people have installed two sets of pumps and pipes, spending much money. A single mono-block pump with single delivery pipe to the overhead tank is adequate. The pump can easily be fitted within the setback area.
There can be two suction pipes with gate valves, one fitted to public water and the other to the rain water tank. To pump up water from public supply, we need to open the valve of that sump and keep the rain water pipe closed.
When it rains and water collects, open the rain sump valve and close the public supply sump valve. It is important to keep pumping up the rain water whenever it fills the sump to maximise the benefits of harvesting.
Considering that the rain water is free, we can construct it to any volume as our funding may permit, but it is safer to maintain a minimum of 6,000 litres.
In cities with tanker water supply that can be ordered by phone, the tankers come with 6,000 litres and they would fill only one sump tank. In case of grey water tanks, they need not be placed close to the rain sumps, since no pump or pipes can be shared between the two.
It is fair on people to feel that managing both public and rain water is a difficult logistics, but if we realise how simple it is, it is our duty to manage it.
In case we require a sump for public water supply, it can be positioned slightly lower than the setback ground level, to regain the site space for a green patch, vehicle parking, outdoor seats or such other possibilities.
It is strange to see how we tend to classify design and construction decisions as important or ignorable and then act upon them accordingly. Those felt to be less important issues suffer for no fault of theirs, water sumps being part of this list of the ignored.
If we ask building owners how much time and attention they have paid towards the water sumps, the majority would be surprised and then may say how minimum it has been.
In most projects, the team would discuss the location of the sump without going over the options, specifications and the budgeting which if discussed could be judiciously resolved. Building owners simply go with the project team who, more often than not, advise larger sumps to avoid possible future complaints, of course at the cost of the owners.
Surprisingly, one reason for the sump size to get reduced is lack of space in the setback to build a larger one! It is a fact that 24 hours supply with good pressure eliminates the need for a sump for individual houses and surprisingly, per person per day need for water would be the same irrespective of water coming directly or through the sump.
In case we require a sump for public water supply, it can be positioned slightly lower than the setback ground level, to regain the site space for green patch, vehicle parking, outdoor seats or such other possibilities. Only the manhole cover, required to get into the sump for maintenance, needs to be at the normal ground level.
To enable stepping down, no mild steel members should be inserted, though the plastic frame steps can be tried. However, using a ladder to get down instead of inserting any kind of step members eliminates wall joints, hence reduces the danger of seepage. With new kinds of mechanised tank cleaning systems now being introduced in large cities, the need to get into the tank is slowly being eliminated.
Unless the soil condition demands so, there is no need for a RCC tank, which today has become a mindless routine practice among many builders. With lesser consumption of money and material, normal brick tank with mesh plastering does the same performance. If the inside is painted with anti-fungal paints or paints specially prepared for water tanks, maintenance jobs also reduce drastically.
Most of us are familiar with the morning sound of water pump, called the monoblock pump. Nowadays it is being replaced by the submersible pump, a three-times costlier option with more silent operation. Technically the monoblock option continues to be a good one considering its pricing and long life, if the muffing sound is not unbearable. In the event of minor repair, it is also easy to check them out.
However, as time changes, our practices also change. Let us accept the new in case of technical advantage, but question if it harms the nature to benefit only the few.
Instead of a blind practice, the frequency of municipal water supply and family size should together decide the ideal volume of storage required, to avoid both dead investment and unhealthy water.
What has a water storage sump got to do with an eco-friendly approach? If you think they are unrelated, you are in for a surprise. It is that grey area most house owners do not think about and builders simply follow a routine without ever wondering about the right practice. The fear of water scarcity in cities like Bangalore adds fuel to the fire with people building larger and larger sumps, spending much money on them. The idea of sump impacts water consumption, construction costs, water stagnation, setback space utilisation and such other indicators of a green home.
We all know that stored water does not stay fresh for too long, a point to reckon with while planning capacity of idle storage in sumps and tanks together. As per survey data, urban dwellers use 150 to 200 litres per day per person, so a family of five needs around 750 to 1,000 litres of water every day. This figure covers all tasks including drinking, cooking, cleaning, bathing, vehicle washing, gardening and occasional extra use due to guests or events. There are many families living with less consumption by avoiding car wash, lawns, high flow fixtures, large built-up area, hardy plants or activities in flowing water. However it is safe to assume the average consumption for size calculations.
How it works
If the city water supply comes every alternative day and we have an overhead tank for 2,000 litres and a sump for 5,000 litres, in every refill less than 2,000 litres out of 7,000 litres gets replaced. Over time, there will be more of old stagnant water than fresh water in the tank. In other words, instead of a blind practice, the frequency of municipal water supply and family size should together decide the ideal volume of storage required, to avoid both dead investment and unhealthy water.
For most families, a sump for 3,000 and overhead tank for 1,500 litres is more than sufficient for municipal supplies. It also fits into the theory of sump being double the capacity of the overhead tank. Virtually, every family has the habit of daily pumping up as a morning routine; as such, the previous day’s consumption, which may never cross 1,500 litres, gets refilled in the tank. In the event of power cut or being unable to pump up on a given day, the tank storage would suffice for the second day also. The sump and tank together can hold up to 4,500 litres, adequate for a minimum of five days for a family of five. If water gets supplied every two or three days, at least half the stored water gets replaced during the supply time, reducing the risks of water stagnation.
The eco-conscious can further reduce this total storage capacity based on the lifestyle of the family, but should not be increased unless specific reasons demand so.