Plywood is used by builders in fabricating cabinets, flooring, furniture, structures, roofs and much more. This widespread use stems from some of the advantages of plywood, such as its strength, ability to be applied internally or externally and variety of finishes and thicknesses. Plywood does have disadvantages, though. Understanding these issues and following manufacturer specifications will help prevent the worst of these problems. Using the proper grade and thickness of plywood is important, as well.
Plywood is created by layering thin sheets of wood at 90 degree angles, which are then held together with adhesives. Occasionally weak spots or gaps can occur in these sheets, leading to voids or hollows inside of the plywood. These voids can often be seen in the edges of the piece of board and cause nails to hold less effectively.
Plywood will expand when exposed to extreme heat or moisture. When boards are installed completely flush with one another, the plywood has no room to grow and will begin to pucker as it expands. Building expert Tim Carter recommends on his website Ask the Builder that plywood be installed with a 1/8 inch gap around the edges to prevent puckering.
Because plywood is fibrous, it will easily absorb water and water vapour, causing it to bubble or delaminate. This problem in most pronounced in outdoor applications of plywood, where tehy are constantly exposed to the elements. Prevention is key since plywood that has begun to delaminate and warp will not return to its original shape and size. Sealers, paints and varnishes can prevent this problem by protecting the plywood from absorbing moisture.
When cost is an issue, alternative wood panelling products are available. Both medium-density fiberboard -- MDF and oriented strand board -- OSB, can be used in many of the same applications as standard plywood for a lower cost. To ensure a project's success, follow manufacturer guidelines for installing OSB and MDF, many of which are similar to the guidelines for plywood installation.
Plywood sheets can quickly become dangerous in high winds both before and after installation. When working with plywood, builders should be aware that the large surface area of plywood sheets can capture gusts of wind and knock the holder over. If not installed securely, high winds can loosen these sheets or even tear them from the structures they are nailed to. Spacing nails six inches or less apart will ensure that plywood is affixed tightly.