Countertops are amongst the most utilized surfaces in a home or commercial building and therefore need to be strong and robust enough to withstand frequent use. If they are not fabricated or installed correctly, this can lead to a number of problems such as:
- Cracking and rupturing
- Chemical stains
- Water damage
Section 11 of the Architectural Woodwork Standards (AWS) provides information and specifications on countertops manufactured from wood, high pressure decorative laminate (HPDL), solid surface, engineered stone, epoxy resin, solid phenolic, and natural stone products.
What to Look Out for With Countertops
- Choose your substrate carefully – different materials should be used for different applications. For example, if harsh chemicals will be used in the space, this will lead to a granite or marble countertop becoming dull over time.
- Chemical and stain resistance – this is affected by concentration, time, temperature, humidity, housekeeping, and other factors. To avoid this issue, it is recommended that actual samples are tested in a similar environment with those agents.
- Placing sinks in a countertop – if the countertop includes a sink, this means that you need to use a certain type of substrate. Veneer core plywood with type II adhesive and industrial-grade particleboard or fiberboard with a 24-hour thickness swell factor of 5.5% or less is required at sink tops and splashes.
If your project is QCP-certified, you should note that the new AWS requirements allow the manufacturer to dictate how countertops are installed on a project. This is a departure from previous specifications as it allows greater flexibility in how countertop supports and spans are manufactured and fitted.
Typical Problems with HPDL Countertops and how to Avoid Them
High pressure decorative laminate (HPDL) countertops are probably the countertops that cause the most frequent problems. Most woodworkers are familiar with the basic construction of an HPDL countertop, which has a deck covered with horizontal-grade laminate. There is a core which, depending on the application, can be standard particleboard or in cases of sink locations, moisture-resistant board.
The following problems generally occur after laminates have been fabricated and installed:
- Cracking at corners and around cutouts – typically caused by one or a combination of improper climate control, improper bonding, forced fitting and poor planning. To prevent cracking:
- Use proper climate control
- Ensure seams are properly placed during the layout of the laminate to minimize stresses
- Separation of the laminate from the core – generally caused by a poor adhesive bond. The bonding procedure should be reviewed with close attention to uniform glue line, uniform pressure, and cleanliness of mating surfaces. If the edges fail to bond, extra adhesive may be applied and the product can be re-clamped. Some cleaning agents, excess heat, and moisture can contribute to bond failure at joints and edges.
- Blistering or bubbling of the laminate surface away from the core can be caused by excessive heat, a starved glue line, improper conditioning, and inadequate pressure or drying. Use of a PVA glue line and pressure over clean, conditioned laminates and core can help prevent this problem. A small blister or bubble and a darkening of the laminate can be caused by continual exposure to a heat source, so lightbulbs and electrical appliances that produce heat shouldn’t be placed in contact with or in close proximity to laminate countertops.
- Cracking in the center of the sheet may be caused by the core flexing when it covers a wide span or by spot gluing. Wide spans call for sturdy framework so the uniformity of glue lines and gluing pressures are important. Care should also be taken to avoid trapping foreign objects between the laminate and the core.
- Warping of the assembly – almost always caused by unbalanced construction or unbalanced glue lines. Proper HPDL backer sheets should be used and aligned so that their grain direction is parallel to that of the face laminate. Proper gluing and conditioning are also important.
You’ll find all the information and guidance you need about countertops in Section 11 of the latest edition of the Architectural Woodwork Standards. This section covers countertops in detail, as well as compliance requirements.
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