Sealants, commonly referred to as caulking, are widely used in the multifamily building industry. Over the past few decades, we have come to rely heavily on sealants to prevent rain penetration into our buildings. However, in many cases, building owners are unaware of the presence or condition of these sealants and of the need for their replacement. Worse, when leakage occurs, often caulking is not replaced, but rather a new bead applied over the existing and deficient caulking.
Application and installation
Caulking is used to seal joints between dissimilar building materials and control joints. In many cases (face sealed building walls), caulking is part of the primary line of defence against water penetration or air infiltration. In such cases, these sealants must work flawlessly at all times. In practice, this is rarely the case, and leakage may occur before a deficiency is discovered.
Ideally, building envelopes should be designed such that no caulking or only a minimal amount is required. However, sealants have too frequently been thought of simply as plugs for cracks or joints between building components. Since caulking needs to be maintained regularly, the associated costs need to be carried in the operating or reserve fund budgets.
Many types of sealants
There are many different types of sealants; each has its own application. All sealants have the same function - to seal the building. In order to achieve this function, sealants must have certain characteristics:?
- They have to be flexible enough, even under cold weather conditions, to accommodate joint movements.
- They must adhere well to the substrate to prevent debonding when being stretched.
- They must be durable and resistant to ultraviolet degradation.
When in need of caulking replacement, it is strongly recommended that proper specifications be prepared by an engineer and that such work be tendered and inspected. More often than not, unqualified workers are hired to carry out this important maintenance work. The result is a poorly performing joint sealant.
Except for temporary and emergency measures, there are no circumstances where caulking should be left in place before new caulking is applied. If correctly done, the existing caulking is removed entirely and the surfaces cleaned. In most cases, a backup rope or backer rod or other bond breaker is installed at the back of the joint before the new caulking is applied. For caulking to work properly, it must adhere on two sides only, and it must have proper contact surfaces.
Life expectancy of caulking
While manufacturers claim that caulking lasts up to 20 years, experience has shown that field applied caulking will last from seven to 15 years. Therefore, a prudent building owner or property manager will institute a regular caulking replacement program.
Caulking can fail in a number of different ways. Mostly, caulking hardens with age and then cracks or debonds. This type of failure is referred to as cohesion and adhesion failure, respectively. Shortly before this stage is reached, caulking should be replaced. In many cases, joint sealants fail prematurely because they are poorly installed. An experienced inspector will be able to identify the impending need for caulking replacement and advise the building owners or property managers accordingly.
Know when not to seal joints
If areas of air or water penetration were previously unsealed, a judgement must be made as to the consequence of sealing these areas. Many window and wall systems are designed to allow water entry which is channelled back to the exterior of the building through interior gutters or weeps. Sealing of these openings would cause water to back up and run to the interior, causing serious damage to the structure and its contents.
Similarly, sealing of weepholes in masonry veneer walls may lead to serious deterioration of the veneer due to the extended presence of water during freezing weather conditions. In your zeal to seal, be sure you do not interfere with the intent of the design.
There are typically several miles of caulked joints on highrise and lowrise buildings. The maintenance of these caulked joints is very important to keep moisture out. To achieve a successful caulking job, caulking replacement needs to be specified and inspected by an experienced engineer. Only qualified workers with several years of relevant experience should be permitted to carry out this work. All too often, the important task of inspecting and replacing the caulking is delegated to the window washing crew.
Where caulking is applied on painted surfaces, the paint finish is frequently damaged during the caulking removal process and hence the paint needs to be touched up or replaced entirely in conjunction with the caulking work. Again, this work should be executed by a qualified painter.
As always, a quality job is well worth the price; it will last longer and perform better.