APC: building pathology

16 October 2013

In the second in our series on the 6 core competencies of the Building surveying APC, Ewan Craig discusses building pathology

Building pathology can be seen as a key competency giving building surveying a strong identity and distinguishing it from the other built environment pathways. As such, it brings demands. To understand and make a recommendation on a building pathology matter can demand breadth and depth, often drawing on the knowledge and skills developed in other competencies, for example:

• construction technology and environmental services: how buildings are, or should have been, constructed, the components and materials, and how they interact;
• inspection: an appropriate inspection approach for the specific situation to assess the defect;
• design and specification: how should it have complied with the expected design and any remedial works to be recommended;
• legal/regulatory compliance: to remedy shortcomings in compliance such as those seen in dilapidations; and
  
• conservation and restoration: an appropriate approach towards defects in historic buildings.

Building pathology is also useful to other competencies such as avoiding defects, with awareness of what could become defective in design and specification. The competency may be challenging, but it rewards those developing their ability in other related fields of building surveying and within building pathology itself.

The levels

• At level 1: Demonstrate knowledge and understanding of building defects including collection of information, measurements and tests.

• At level 2: Apply your knowledge to undertake surveys, use surveys and other information to diagnose cause and mechanisms of failure.

• At level 3: Provide evidence of reasoned advice and appropriate recommendations, including the preparation and presentation of reports.
  You should be familiar with the building pathology issues in your submission documents and be ready to address questions and aspects related to them.

Hypothetical questions

Two examples are given below.

1. What factors did you consider in assessing the failure of the wall ties in the survey and investigation of the X 1950s’ house?

The assessment methodology followed BRE Digest 401 and IP 13/90 considering these factors:

• construction: the type of wall, its form of construction, dimensions, any differences in construction. This showed it to be a cavity wall with stretcher bond brick external skin.
• investigation: initially a visual inspection noting cracking/movement to the elevations that was characteristic of wall tie failure with horizontal cracking to the mortar joints regularly at the anticipated cavity wall tie locations every 450mm vertically. The cracking was particularly noticeable to the most exposed elevation.
• testing: once located with a metal detector a sample were inspected with an endoscope to confirm the cavity construction and the initial condition of the wall ties. Some were carefully exposed to assess their condition and ability to function.
• it was found that the majority of the wall ties sampled were correctly positioned but they had already reached total failure, were severely corroded where they had been exposed in the cavity.

2. Why were the pigeons roosting and nesting on the building B a problem for the building fabric and how did you reach your recommendation?

The pigeons were nesting on the cornice of the external wall, on the mansard roof area, roof plant area and some ledges. The building has brick walls with some features in limestone. Damage was visible by the nesting and roosting areas to both of these materials, which are prone to erosion and staining by the acids and soluble salts from bird droppings. There was also a history of the rainwater goods being blocked by pigeon nests, which had led to water damage internally. Health and safety issues to the building users were another aspect but this is not part of the building fabric.

Several methods were considered to control the problem. The aim was to deter the pigeons from nesting and roosting. The client preferred a simple value-for-money solution. With a large area to cover, the life cycle costs favoured a netting system over the roof and plant area, with steel sprung wires to the flat surfaces where the netting could not be raised over it.

Other systems considered were anti-perching spikes, gels and further steel sprung wires. The netting and steel sprung wires were combined with a programmed external redecoration and other remedial works to the exterior, including cleaning and minor repairs to the masonry to reduce costs and potential disruption further. The client has been very pleased with the result.

Care

Given the time constraints of the APC, your answer should give a brief but whole response. The answers given above are not exhaustive; care should be taken to demonstrate your own skills, abilities and knowledge to the assessors.

Ewan Craig is a member of the Building Surveying Professional Group Board and the Course Leader for the BSc (Hons) in Building Surveying at the College of Estate Management

Further information

For more information see the APC pathway guide for building surveyors