Fire damage extends beyond simple combustion. Table 1 (below) attempts to summarise the various mechanisms by which damage is caused.

Structural Repairs
In considering structural repair strategies in general, the basic choice to be made is that between demolition/renewal, and some form of repair. The choice of repair method is then a secondary decision. Schneider proposes a classification for the severity of damage, summarised in Table 2.

Concrete
There is a wealth of information available on the repair of fire-damaged concrete structures. Reinforced concrete is a composite material and it is necessary to consider the effect of the fire on the concrete and the steel components individually, and on their composite action. The most comprehensive single reference is a Concrete Society report.

Steel and Cast Iron
Structural steel is less well served in the literature. The major problem is gross distortion caused by a combination of reduced yield strength, reduced Young's modulus and increased stresses above a critical temperature. This is addressed in a British Steel report , which notes a good recovery of properties on cooling.

The same report notes that cast iron performs well in fire. The main problem is that thermal shock from extinguishment water may cause cracking which has particular implications for the re-use of cast iron beams.

Masonry
There is little information on masonry repair. Schneider notes that if there is no visible gross damage the strength of the bricks may be taken as similar to their original values, due to the high temperatures bricks undergo during manufacture, and that mortar behaves in a similar way to concrete. This is, of course, only true for clay brickwork. Calcium silicate bricks have more in common with concrete and it is appropriate to deal with calcium silicate brickwork, and concrete blockwork in a similar way to unreinforced concrete.

Timber
There is little or no information readily available on how timber performs in a fire, except for data on charring rates, which is available from several sources. The most authoritative is BS 5268 . Schneider places the decision between repair and renewal in damage Class 4 on structural grounds but acknowledges that æsthetic requirements may be decisive even down to Class 1 damage.

Non-structural Repairs
There is little published information on the reinstatement of non-structural components. Therefore, specifiers must work with 'ordinary' maintenance methods for the components in question, or rely on their own extrapolation of those methods.

It is likely that non-structural works are seen as less interesting, and less important than structural works, although survey respondents agreed strongly that smoke and water caused more damage than the fire itself, and such damage is often non-structural in nature.

Management Issues

Dealing with unknown work
By the very nature of the problem, once a fire damage project starts on site there will be variations from the contract. Kinnear and Robery note the difficulties facing the specifier in his investigation work, and it is inevitable that some areas will be inaccessible for inspection.

Therefore, it is important that the specifier should 'expect the unexpected' and plan for it at specification stage. Survey respondents favoured the use of provisional sums or quantities, although there was some support for specifying provisional work items.

Forms of contract
Several of the JCT forms of contract are suitable for use with fire damage projects, the selection depending on the size and complexity of the project, the certainty of the specification and the degree of urgency. A comparison of contract forms is given in JCT Practice Note 20.

Specifiers prefer 'traditional' contract forms, but it would appear that loss adjusters are more adventurous in adopting other forms of contract where there is seen to be an advantage, particularly the Fixed Fee form of Prime Cost Contract.

A need for guidance?
The survey considered the need and scope for a comprehensive guidance note for use by both specifiers and loss adjusters; on the lines of the recent IStructE document on subsidence . Such a document might be justified for several reasons: the promotion of understanding between professions, the need for technical instruction, or to address a perceived problem. However, there was little support for the notion.

Specifiers and loss adjusters were agreed that the insurance industry understands building reasonably well, but not vice versa. Thus, written guidance may assist specifiers in understanding insurance matters but is less likely to be of reciprocal interest to the insurance industry.

It is clear that specifiers are unaware of much of the relevant technical literature that exists. It is also clear that much of the literature is not readily accessible, and that there are large areas (e.g. non-structural repairs) where no literature is available at all. Accessible and digestible technical guidance would be of value to both specifiers and adjusters.

Unlike subsidence, fire damage is usually visible and well defined, and the relevant insurance policy wordings have been refined by market forces and by testing in the courts for decades. The forces causing the subsidence 'problem' of recent years are not present, so there is no need for a formal code of practice to resolve conflicts. Indeed, many loss adjusters and experienced specifiers consider that such a code already exists in unwritten form, and should best stay that way.

Although a comprehensive bilateral code is unlikely, there is real scope for the publication of unilateral guidance notes, which may subsequently gain support and acceptance. This could come from bodies such as BRE or BSI, or from a professional institution wishing to issue technical guidance to its members. Given that the great majority of loss adjusters responding to the questionnaires identified chartered building surveyors as the professionals best suited to fire damage reinstatement, it is appropriate that the RICS, through their Building Insurance, Assessment and Claims skills panel, have produced a guidance note.

Tables

Table 1 - Fire Damage Mechanisms

Table 2: Simplified classification of fire damage (after Schneider)

References

Bedford, C.S.: The repair of buildings after damage by fire: unpublished MSc dissertation, University of Greenwich: 1994

BS 5268, Sect 4.1: 1978, Structural use of timber: Recommendations for calculating fire resistance of timber members.

Concrete Society: Assessment and repair of fire-damaged concrete structures, Technical Report no. 33: 1990

Institution of Structural Engineers: Subsidence of low rise buildings; 1994

Kinnear, R.G.: Investigation of fire-damaged buildings: Structural Survey, v4(1), pp 31-34: 1985

Kirby, B.R. et al: The reinstatement of fire damaged steel and iron framed structures: British Steel Corporation, Swinden Laboratories: 1986

Royal Institution of Chartered Surveyors: Fire Damage Reinstatement; 199?

Robery, P.: After the fire: testing to minimise refurbishment costs; Construction Maintenance and Repair, May/June 1991, pp 17-21

Schneider, U. (ed): Repairability of Fire Damaged Structures, CIB W14 Report; Fire Safety Journal, v16: 1990

The above extracts from the article, Fire Damage: A Need for Guidance? is reproduced with the kind permission of the Bedford Partnership. The article was written in 1995 and is for general guidance only.