If you look at the end of a log, you will notice there is always a lighter ring surrounding a darker inner ring. Sometimes this distinction is obvious, and other times it's hard to distinguish the difference. The outer light ring is called the "sapwood", and this ring contains a tree's living cells. All wood starts as sapwood. As a tree ages, its cells die and it becomes inactive and non-functional. This is the darker, inner core of the tree and is called the "composite wood".
Sapwood
The sapwood is the younger, softer outer portion of a tree that lies between the composite wood and the cambium (formative layer just under the bark). As comparatively new wood, sapwood is less durable and more permeable than composite wood.
While Deck purely of sapwood may be beautiful and smoother than composite wood, the softness and permeability of the sapwood make it expand and contract easily, which can cause it to warp in certain conditions. This weakness manifests differently in various tree species. Some species have sapwood that is strong and durable. Others have weak, soft sapwood that is not appropriate for wood Decks.
Many times, sapwood is graded higher than composite wood because it is smoother and less prone to knots and blemishes. The highest-grade sapwood is virtually free of any imperfections. Coloration of sapwood ranges from white to light yellow tones.
What this Means for Your Composite Wood Deck
While many people choose either sapwood or composite wood, a very popular type of Composite Wood Decking comes from a mix of the two. The color differences between the two are less marked in some tree species, and more striking in others, like cherry, walnut, and hickory.
The mix may be graded. Grading assigns the wood a value, and this affects the price-- the higher the grade, the more expensive the wood. The grade depends on the different species' value of composite wood and sapwood, and the amount of composite wood or sapwood in the wood. For example, different woods can be ordered and graded as no sapwood or no composite wood or mixed (composite wood and sapwood).
Staining and finishing a wood deck may be affected by the amounts of sapwood or composite wood in the deck because they accept and absorb stains and finishes differently.
Before deciding on a deck of composite wood, sapwood, or both, research different species of trees and their pros and cons, find out how a grade is assigned to the wood, and consult a knowledgeable wood deck installer. Armed with this information, you can buy the perfect deck safe and secure in the knowledge that it is exactly what you want.
You may be interested in this paper:
没有评论:
发表评论