Are Foundations Salvaged Following a Fire?

It is quite true to say that the foundation of a building can be damaged in a fire.

However, it is untrue to say that the heat produced by a fire necessarily alters part or all of the concrete foundation. Concrete decreases in strength when exposed to high temperatures and/or to the heat of fires for long periods of time. 

It is necessary to carry out visual and physical tests to ensure that the concrete still retains its mechanical and physical properties. In the case of a partially damaged foundation, the most economical solution is often to keep the unaltered parts rather than to replace them.

   

Many visual and physical techniques are conducted upon assessing a burned foundation. Indeed, some visual evidence can be observed when concrete has potentially been altered by heat, including surface crumbling, color change and some cracks. However, due to the different constituents and types of concrete, the latter can also react differently to heat.

In concert with this visual inspection, a physical assessment is performed with a hammer. The weak material can be distinguished by the distinctive sound that the hammer emits in contact with the weakened surface. By means of a visual inspection and use of a hammer, it becomes possible to delimit the extent of the area possibly affected by the fire. 

Subsequently, tests with a sclerometer are carried out. These are non destructive tests performed on concrete to measure its hardness by comparing the results of various measurements of the apparent compressive concrete strength (a small ball of steel that bounces more or less depending on the material hardness) between an area exposed to heat and an area unexposed to heat.

As a last resort, destructive testing could be done to confirm if the concrete still maintains its minimum characteristics required by the National Building Code. Concrete samples are collected using a core drill for laboratory examination. 

At Pyrotech BEI, our civil engineers can provide an accurate picture of the extent of damage to a foundation that has been potentially exposed to intense or prolonged heat. 

If needed, we can also provide reconstruction or repair guidelines to meet the minimum requirements for the reconstruction of a building while keeping the foundation sound and unaffected by fire.

By: Charles Corsi, Candidate to the Engineering Profession
Civil Engineering | Construction | Structure