Introduction

Historically the majority of repairs to structural timbers have been carried out using traditional methods involving either the use of steel plates and bolts or a variety of timber scarf joints.

Although many of these traditional repairs have been subject to engineering calculation and design, it has to be assumed that the majority of repairs have been based on experience and good judgement.

A major reason for this assumption is that very few contractors in the building conservation industry have their own in-house qualified structural engineers.

For the same reason most structural repairs involving a resin component will not have been subject to qualified engineering design.

The effects of legislation and a greater awareness of contractual responsibilities are leading to increased levels of engineering involvement in the building conservation industry.

Regardless of the repair method adopted there will often be a legal requirement to provide structural calculations.

In the case of upgrading a structure, e.g. increasing the floor loading from domestic to commercial capacity, structural calculations will always be required, hence a structural engineer will be involved from the outset.

Obtaining Structural Calculations

There are three levels of procedure in arriving at a practicable, well-engineered design for the repair or upgrading of structural timbers - collating information, relaying information to a central point and joint assessment.

1. The surveyor collates accurate information on the problem to be solved by completing a PRS Enquiry Form. The inclusion of diagrammatic information is most important and should be included wherever possible.

2. The surveyor relays the above information to a Structural Engineer together with the various material reference values. At this time the engineer will be able to complete his design calculations which may incorporate the various standards such as BS 6399 Part 1, BS 6399 Part 3, BS 4978 and BS 5268.

3. The Engineer's design is passed back to PRS for confirmation or adjustment of their preliminary design, on which a Cost Estimate will have been based.