Steel frame or concrete block inner leaf?


Housing consumer survey

Tom Hughes
Nottingham Trent University
UK
tom.hughes@ntu.ac.uk

Related web sites:
Foursteelwalls: Steel research house project
Architectural Design, Global Difference research group
Architectural Construction Research Group


About the survey

A postal survey of 508 addresses in the Nottingham (UK) area was carried out in Jan/Feb 2004. The survey was designed to reveal whether there is a preference for either concrete block or steel frame structures among homeowners and buyers. The following is a summary of some of the findings.

Key issues

The key issue of the survey was the choice between steel frame and concrete block as the main structural material for new houses.

Houses in England are conventionally built with cavity walls made up of two layers. The inner layer of concrete blocks does the main structural work of holding up the floors and roof, while the outer layer (usually of bricks) governs the appearance of the house.

There are alternatives to the use of concrete block for the inner, structural layer. One of the alternatives is to use structural steel framing, which is then enclosed by an outer layer of brick or another cladding material. This method has been in use in other countries for many years and in some places is very common. More recently, it has been introduced to this country, and an increasing number of houses are being built this way every year.

Opinion survey

Section 1 of the survey consisted of an attribute-based stated preference model, the results of which have been analysed elsewhere (Hughes and Burton, 2004 (forthcoming)). Section 2 of the survey contained the following 22 opinion-soliciting questions:

For this exercise you are asked to compare two houses of similar size, price and location. One is being built with a steel frame and the other with a concrete block structure. Please answer the following questions by ticking the box that best indicates your opinion.


Responses to the opinion survey

127 completed surveys were returned, a response rate of 25.2%. Some basic analysis was carried out to check the representative nature of the sample (see Figure 1: Respondent profile chart)

Figure 1: Respondent profile chart


Sets of issues

The following groupings of ‘issue-sets’ and associated questions can be made:

·Financial: Q7 (mortgageability), Q8 (insurance/guarantees), Q26 (saleability), Q27 (maintenance of value)
·Construction: Q9 (speed of completion), Q10 (defects), Q11 (finishes quality), Q12 (construction quality), Q28 (permanence)
·Design: Q13 (external appearance), Q14 (room layout), Q15 (security), Q16 (storage space)
·Performance: Q17 (maintenance costs), Q18 (comfort temperature), Q19 (sound insulation), Q20 (heating bills), Q21 (fire safety)
·Adaptability: Q22 (extending the house), Q23 (changing room layout), Q24 (furniture and fittings), Q25 (DIY work)


Balance of respondent opinions

An ‘opinion index’ was created to measure the balance of opinions about steel frame and concrete block.

Against each issue-set the index was negative, indicating a balance of opinion against steel frame. However, the degree of ‘negativity’ varied considerably across the issue-sets (see Figure 2: Balance-of-opinion index), construction showing the most positive response and financial aspects the most negative.



Figure 2: Balance-of-opinion index

A difference in resistance to steel frame according to age was predicted. In order to test this, a balance of opinion index was calculated for two age groupings, those aged 44 and under and those aged 45 and over. Those under 45 demonstrate a less negative opinion towards steel frame on each of the issue-sets, and for ‘construction’, their balance of opinion index is actually positive (see Figure 3:Balance-of-opinion index for two age groups).

Figure 3: Balance-of-opinion index for two age groups

There were also variations in the extent to which the issue-sets were controversial. Some issues-sets attracted a large number of neutral responses (“both the same” or “no opinion”). This is illustrated by plotting a quadrant chart of the balance of opinion against controversy (gauged by percentage of neutral responses) (see Figure 4: Balance of opinion against controversy)

Figure 4: Balance of opinion plotted against controversy (proportion of neutral answers)

It is clear from Figure 5 that the issues that should be of most concern in the marketing of steel frame house are financial matters, adaptability and performance issues. Each of these has a strongly negative rating and a high level of controversy. Design attracts low levels of controversy (many neutral responses), whilst construction is more controversial but, on balance, is only weakly negatively perceived.

Each of the issue sets will now be dealt with in more detail to examine some underlying effects.


Construction-related issues

The construction issue-set was examined through the following questions:

In your opinion, which house is likely to …

· Q9: … be completed more quickly, ready for moving in?
· Q10: …have fewer defects on moving-in day?
· Q11: …have a higher quality of finishes?
· Q12: …have a higher quality of construction?
· Q28: …have a more permanent structure?

The overall distribution of responses for the issue-set is shown in Figure 5: Construction issue-set responses

Figure 5: Construction issue-set responses

Positive and negative opinions were evenly balanced, with 73% of responses ‘neutral or better’ with respect to steel frame.This is the issue-set in which steel frame best ‘holds its own’with concrete block, but a more detailed breakdown (see Figure6: Construction issue-set responses breakdown) reveals considerable variation across the issue-set questions:

Figure 6: Construction issue-set responses breakdown

Speed of completion is steel’s strongest attribute of those tested, though it is perhaps worth pointing out that quick completion may have negative as well as positive connotations.

Another very positive result for steel frame is seen in relation to defects. Positive responses outweigh negative by a ratio of 3:2, which might suggest that there is an understanding of the potential for framed construction to reduce defects, or possibly a perception of steel as a ‘precision’ material.

It is interesting to note that the defects question receives the highest level of ‘no opinion offered’ responses (the second highest level of ‘no opinion…’ responses is seen in response to the quality of finishes question). The reasons for this would have some bearing on any decision to adopt a positive marketing approach to steel frame; further research could test the hypothesis that steel frame is seen in a positive light with respect to construction quality but that there is a low level of knowledge in this area.

Perceptions of impermanence might prove to be a problem for steel frame, with concrete block showing very strongly in this category.


Design-related issues

The design issue-set related to the following questions:

In your opinion, which house is likely to…

· Q13: …have a more attractive appearance from the outside?
· Q14: …have a good layout of rooms internally?
· Q15: …be more secure (difficult to break in to)?
· Q16: …have sufficient storage space?

The overall distribution of responses for the issue-set is shown in Figure 7: Distribution of responses for design issues-set.

Figure 7: Distribution of responses for design issues-set

Negative opinions of steel frame slightly outweigh positive opinions, however the majority of responses put both systems on level terms, and 75% of responses were ‘neutral or better’ for steel frame.

A more detailed break down (see Figure 8: Design issue-set responses break down) reveals that responses show some variation across the questions. Steel frame performs most strongly on the room layout question, suggesting that perhaps there may be some awareness of the potential for increased flexibility in planning that framed construction allows. There is more caution about the external appearance of the steel framed house, with just 6% of respondents expecting steel frame to have a positive effect.

Figure 8: Design issue-set responses break down


Financial aspects

The financial issue-set related to the following questions:

In your opinion, which house is likely to…

· Q7: …be easier to get a mortgage for?
· Q8: …be easier to get insurance/guarantees for?
· Q26: …be easier for its owner to sell quickly if he/she needs to?
· Q27: …maintain its value better (have a higher resale price)?

The distribution of responses for the issue-set is shown in Figure 9: Distribution of responses for financial issues-set

Figure 9: Distribution of responses for financial issues-set

Negative opinions of steel frame strongly outweigh positive opinions, however 38% of responses put both systems on level terms, and 51% of responses were ‘neutral or better’ for steel frame.

A more detailed break down (see Figure 10: Financial issue-set responses break down) shows that responses are reasonably consistent across the questions. Steel performs most strongly on the mortgageability question, and least well on the question of ease-of-sale. This hints that respondents may have concerns about ‘storing up trouble’ for the future by building with a system that will be more difficult to sell than it is to buy.

Figure 10: Financial issue-set responses break down

By contrast, concrete block housing performs more strongly on the questions relating to future financial performance, suggesting that it is seen as a sound investment for the future. These effects are not pronounced, however, and more detailed analysis would be required to establish their significance.


Adaptability-related issues

The adaptability issue-set related to the following questions:

In your opinion, which house is likely to…

· Q22: …be easier to extend (build on to)?
· Q23: …be easier to adapt (change the internal layout of rooms)?
· Q24: …allow easier wall hanging of furniture and pictures?
· Q25: …be easier to maintain and refurbish using DIY methods?

The overall distribution of responses for the issue-set is shown in Figure 11: Distribution of responses for adaptability issue-set

Figure 11: Distribution of responses for adaptability issue-set

The adaptability issue-set shows the most favourable overall result for concrete block, and the lowest proportion of neutral responses. This suggests that adaptability is one of the most problematic area for the marketing of steel frame; the low proportion of neutral responses signifying few consumers who would be easily persuaded by a positive marketing campaign.

The detailed breakdown of responses across the issue-set (see Figure 12: : Break down of responses to adaptability issue-set questions ) reveals that the pattern of strong results for concrete block and few neutral answers is consistent across the questions.

Figure 12: Break down of responses to adaptability issue-set questions

Concrete block scores highly in terms of how easy it would be to extend (build on to), whilst steel frame scores well in respect of changing internal room layout. These results are consistent with previous observations about room layout and the difficulty of finding skilled labour for building work.


Performance-related issues

The performance issue-set related to the following questions:

In your opinion, which house is likely to…

· Q17: …have lower maintenance costs?
· Q18: …be easier to keep at a comfortable temperature inside?
· Q19: …be quieter (have better sound insulation)?
· Q20: …have lower heating bills?
· Q21: …be safer in the event of a fire?

The overall distribution of responses for the issue-set is shown in Figure 13: Distribution of responses for performance issue-set

Figure 13: Distribution of responses for performance issue-set

The distribution of responses for the performance and financial issue-sets is similar. Negative responses heavily outweigh positives in both cases, and although there is a higher level of positive response towards performance issues, a relatively large proportion of neutral opinions remain. As with financial issues, this suggests that performance issues could be tackled as part of a positive marketing campaign.

The detailed break down of responses (see Figure 14: Break down of responses for performance issue-set) reveals some variation across the set of questions.

Figure 14: Break down of responses for performance issue-set

In particular, steel frame performs relatively well with respect to maintenance costs, with a similar proportion of positive responses to concrete block. This could be regarded as inconsistent with the concerns about permanence identified previously, but is consistent with the high regard shown for quality of steel frame construction. Further research might be targeted at perceptions of construction quality, maintenance and permanence with regard to steel frame.


Tom Hughes March 28 2004
Nottingham Trent University
UK
tom.hughes@ntu.ac.uk