"Matters for consideration when doing Additions and Alterations Works"
If the changes to the existing fabric of the house are major, it could be beneficial to rebuild completely. Apart from getting a brand new house, the financial merits of a higher property valuation means that whatever you are spending, is locked into the property. Most additions and alterations have only some effect on the valuation of the completed property, and sometimes insufficient to cover the total amount of money invested in the property. In a nutshell, its like putting in money with no recourse for recovery (if and when you sell the property). It would be wise to check out your investment position…talk to your mortgage financer.
Apart from the numbers, there are also a number of pragmatic considerations in rebuilding an old property:
Thanks to the efforts of the Building and Construction Authority, today’s buildings are built to a much higher standard than in earlier years. For instance, concrete is now factory mixed and subjected to much better supervision and quality control. With higher industry training and regulation, you will find that nowadays reinforced concrete is more compact (with fewer air pockets within the mix) and has higher structural strength.
The differing standards of the ‘old’ and ‘new’ parts of a house could in some extreme cases underline the problems for major A&A works in old houses. When a new section is ‘joined’ to an existing property, the old (and possibly poorly built) structures may cause minor fissures to open up within the old fabric as they cannot withstand the mechanical forces which are asserted by new structures. These are sometimes seen as cracks on the floor, wall or ceiling finishes.
A slight foundation settlement may also cause hairline cracks to appear on brick walls, or floor slabs, between ‘old’ and ‘new’ sections of a house. Whilst a major settlement could result in structural failure, it is relatively rare and usually the challenge is more of a visual imperfection.
Many a house in Singapore, has over the years since being built have parts of it extended in the form of simple extensions. These could involve outdoor terraces, new party walls, kitchens and other outdoor extensions. And quite often, these outdoor areas are built without proper firm foundation.
The problem starts when new owners of a property decides to enclose an otherwise outdoor space, into indoor areas. When these spaces are enclosed, usually the finishes are upgraded and that’s when hairline cracks, which didn’t matter previously, start to affect the aesthetics of the house. Sometimes the onset of a major A & A is precipitated by the many cracks that appear despite many attempts to correct it. It is important for you to highlight to your builder specific areas (like cracks) that require to be fixed, and not hope for it to miraculously ‘disappear’ after the completion of A & A works. Superficial plaster patch-ups are easy to forge, but could very well re-appear if no underlying longer-term solution has been done to address the root of the problem. A good an experienced builder should be able to spot the problematic areas.
Since the collapse of Hotel New World, new building projects, including houses, now need soil analysis – an investigative, lab-style investigation of the inherent soil characteristic which supports the house above it. In practical terms, this means that an extension to your house requires written solid justification as to the type of foundation that is required. It does not matter if the house built in the 50’s, was built on concrete footing foundation and that now, to save cost, you’d like it to have the same type of foundation. In other words, you could have part of the house sitting on concrete footing foundation and the other new half, on piled foundation.
A possible problem is that if the old section does not sit on a piled foundation, it will obviously be ‘weaker’ than the new piled section. A differential settlement can obviously happen, and can be a source of future problems like cracks in the walls and floors.
In doing A&A works, consideration has to be given to the existing type of construction, total structural loading, and the condition of the existing concrete structures. As A&A works could introduce new additional loadings to the existing fabric of the house, it could involve strengthening existing structures like foundation, columns and beams.
Remember that if an existing house has inherent problems, an A&A may not solve all the problems arising from poor construction practices of the existing building. It can at best mitigate somewhat the ‘old’ problems provided it is practicable to do so. At other times, it may just not be worth the additional costs.
We have over the years, occasionally encounter surprisingly poor construction standards. Sometimes we find strange stuffings in concrete, from paper to bottles, thus presenting a ‘hollow’ sound when the surface is pounded. This ‘hollowness’, if sufficiently material is a structural weakness which should be addressed so that the concrete slabs can support the loads expected of it.
A lot of old concrete suffer from spalling concrete which is a result of steel bar corrosion. Steel bars when corrode, will expand and its expansion forces the concrete which envelopes it, to crack. When the crack appears on the surface, it is seen as a cracked surface and the corroded bars become visible. Old reinforced concrete specifications have too thin a layer to lap over the steel bars, thus the problem in older building. This situation is exacerbated if smooth steel bars are involved, which is usually the case in older buildings of 20 years or more.
Many old buildings also does not have a damp-proof membrane, or if present, the layer could have disintegrated through wear and tear. Therefore, if you are considering having marble or granite finishes on the floor of an old house, especially white marble, you should reconsider against having it. If there is rising moisture on a concrete floor, home-owners may have to contend with stained marble or granite in the years ahead. While there may be a simple remedy of applying waterproofing compound on the slab though, it cannot beat the robustness of a well-installed damp-proof membrane.
Whilst a new layout can be customised to fit the home-owner’s current needs, existing columns and beams could pose a problem as the new design must work around them.
Hidden structures can cause problems in A&A works, especially if they are not indicated in the drawings lodged with the authorities. In many of our remodelling projects, we have discovered abandoned pipes, cables, appendages and sometimes even columns and beams which were not supposed to be there. Some could have been the result of unrecorded works done over the years, or even older structures which were incompletely demolished. These could affect the new layout of the house.
The comparatively low ceiling of old buildings poses another problem in A&A, particularly on upper floor areas with new toilets. Sewerage pipes, which are built on the underside of toilets, could lower the underlying ceiling of the lower floor even more resulting in a ‘squat’ interior. While some design strategies can overcome this challenge, nevertheless it may compromise the desired effect of spaciousness.
When a new toilet is built onto an existing concrete floor, there are several challenges to be tackled. Apart from the route of water supply and sewerage pipes, there is a need to be very careful with passive water barrier. Whilst the situation can be overcome by careful detailing and supervision, many builders may not be aware of the calibrated limitations of such detailing. While there may be no visible consequences over a short term, poor detailing can cause leakages that can undermine reinforced concrete, and floor, wall and ceiling finishes.
Bathroom/toilet systems can be a source of irritation with water gushing through the plumbing pipes, especially in the quiet of the night. In A&A, the home-owner may need to consider the location of these new facilities – more so if they are situated symmetrically from your neighbour’s bedroom or study.
In this respect, Meridian Homes® has developed the proprietary SilentFlo® Drain to eliminate the water noises and minimise any disturbance.
Some old buildings face the problem of ‘weeping’ floor slabs, particularly at the car porch and/or side apron of the house. These are typically caused by a high water table, or high surface water run-off, which may seep out of such joints.
Such ‘weeping’ is inevitable for this type of construction detailing. Whilst an A&A works can somewhat mitigate this problem, however the design and detailing must be correctly strategised and incorporated right at the start of the construction process.
In any major A & A, if the decision is to retain as much of the existing fabric as possible, there is one thing the home-owner should do – gut out the infrastructure, particularly the plumbing and electrical works.
Retaining, and living with, the multiple joints and bends in old pipes and cables is really asking for trouble. As pipes and cables lose their efficacy with time, the home-owner may face such problems as high water and electricity bills, or disruptions like power trips and blackouts. In electrical cable connections, there is the added danger of fires; in water pipes, it could be leakages.
