Disability digest: Conventional Design versus Universal Design – A comparative study

Economic benefits of making built environment accessible to persons with disabilities – Case Study Stockholm - Sweden Cont’d

From the cost comparison method, "is non-handicapping design more expensive than "conventional design?" was a subject of investigation.

The findings were deemed to be both intuitive and useful. First, cost comparisons can be done in two ways. One, an existing inaccessible building is to be brought up to certain accessibility standard through renovation. What does this renovation cost? Compared to the original construction costs? Second, given an inaccessible building, what would have been the costs, if it had been constructed with universal access right from the beginning? Most often, the studies only take up one type of comparison.

For example, in a US study (Schroeder and Steinfeld, 1979) different types of existing structures were subjected to the two comparisons. The results are summarized in Table 1. Table 1: Cost increases due to accessibility in public buildings. Renovation and original non-handicapping design compared to conventional (inaccessible) structures. Source: Schroeder and Steinfeld (1979), ‘The estimated cost of accessible buildings, US Department of Housing and Urban Development’.

Regarding the first type of comparison, what is the cost of accessible retrofitting compared with original construction costs? The estimates range from 0.12 per cent to 0.5 per cent. The other comparisons, how much more it would had cost, if the structures had been designed without barriers right from the beginning? This range from 0.006% in the case of the shopping centre to 0.13% in the case of the college classroom.

In Singapore in 1980 the Singapore Urban Redevelopment Authority conducted a similar study by making cost comparison for a large centre consisting of commercial offices, multi-storey car park, food centre and market. During the study, a controlled costing exercise was carried out to compare the cost of the building with and without facilities of access for persons with disabilities, and the conclusion was that these could be provided for by an additional 0.11 per cent of the total cost.  

With regards to a multi-family housing, a French study estimated the additional costs for bringing up multi-family housing to accessibility standard, on an average, ranged from between 0.5 and 1.0 per cent of total construction costs in new construction. The Swedish Building Research has also made the near estimates for multi-family housing. The Australian Uniform Building Regulations Coordinating Council that also undertook comparative cost studies reported an almost identical result as in Wrightson and Pope (1989). Phillipen (1993), a study in Germany on multi-family housing revealed that the differences in cost between traditional (real inaccessible) construction and the new type of non-handicapping building construction is negligible.

In Ottawa, a Canadian research on single-family units was also carried out. 9 specially designed units in a project of 54 townhouses cost 8 - 10 per cent more than the others but added only 0.5 per cent to the overall project cost. The effect on rental scale is therefore negligible. However, this cost comparison does not involve universal access, since the other 45 townhouses apparently were not accessible.

Also report by the Canadian Mortgage Housing Company of 17 case studies indicated that, in most cases, the accessibility features added 0.39 - 0.53 per cent to the building cost.  Dunn (1993) in his study of "Project Open House" reported, an average of only $1,500 was spent in 1986 to adapt existing homes of consumers to make them accessible. He also referred to a US study by Bartelle Memorial Institute which found that if accessibility is incorporated into a design prior to construction, the cost of making 10 per cent of the units accessible are less than 1 per cent of the total constructions costs.

In the United States, different studies by U.S. Housing and Urban Development (HUD) have estimated the costs of "adaptable" housing, which is a housing scheme with basic access features that easily can be complemented by individuals as needed. The findings were about one-half of one per cent of new construction costs. In the same vein, Housing and Urban Development (HUD) study for guidelines for the Fair Housing Amendments Act of 1988 showed an average cost increase of 0.5 per cent in typical single-family homes in four suburban projects.   

The US study conducted by Schroeder and Steinfeld (1979) already mentioned above also contains housing examples as shown in the following table. Table 2. Cost increases due to accessibility in residential buildings. Renovation and original non-handicapping design compared to conventional (inaccessible) structures. Source: Schroeder and Steinfeld (1979), ‘the estimated cost of accessible buildings, US Department of Housing and Urban Development’.

The results of this study indicated that accessible renovation amounted up to 21 per cent of the total construction in single-family units and to a maximum of 1 per cent in high-rise multi-family apartments. Designing the structures from the very beginning as non-handicapping would have only amounted 3 per cent in their single-family example and 0.25 per cent more in the high-rise complex they studied.

In interpreting the studies presented so far, one can derive several conclusions. The most obvious result is that renovating existing buildings is much more expensive than   building the same structure with barrier-free design from the beginning. The latter is between 4 and 35 times cheaper (see Col 1/Col 2) in the tables. Single-family homebuilders often point out that even in the case of new construction the additional costs due to access features will be far too high for the market, implying that nobody would buy their accessible houses.

When analysing their cost estimates, Park (1993) found out that often builders have not changed their thinking and see access as a matter of adding on extra features rather than incorporating access already in the basic design. "Stretching" old plans to meet particular elements of new design requirements makes them more expensive than re-designing anew. A relatively small investment in architectural costs will result in lower construction costs for access. Some concluded that access legislation would raise new construction costs in public buildings by less than 0.1 per cent, on an average, in multi-family housing by up to 3 per cent in single-family homes - single floor.

It is probably safe to assume that once architects, builders and suppliers’ experience with non-handicapping design has become deeper and more widespread, costs will come down considerably, the report concluded.