Wood

What is the stuff that really works? Where to get it. Why do you like it?
johnleeke
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Wood

Postby johnleeke » Mon Feb 09, 2015 6:57 pm

Wood

Old Wood vs. New Wood
Old wood found in American historic buildings is often "old-growth" wood, which grew slowly for two main reasons. It grew up naturally in a mature forest with a limited amount of sunlight, and it grew when the climate was colder. This very slow growth means there is a higher ratio of latewood to earlywood, which in turn gives the wood desirable characteristics. It is stiffer, stronger, more stable, more decay resistant and holds fasteners better. Windows made before 1900 are more likely to be made of old wood. Old wood is also known as “first-growth” wood. Windows made from 1900 to 1940 may be made of “second-growth” wood that may have less desirable characteristics, but is still more durable and suitable for window work than new wood. The current forestry practice is to grow wood as quickly as possible by thinning forests. In addition, the climate is warmer than centuries ago thus accelerating growth. This results in new wood that is susceptible to decay, is unstable, and is not suitable for window preservation work.

The age and character of wood can often be determined by examining the end of the board or plank. Old-growth wood often has more than 30 growth rings per inch. Second-growth wood may have 15 to 30 growth rings, and new wood may have a few as 2 or 3 rings per inch.

Species
Some species of wood are more suitable than others. Decay resistance, paint holding, stability and machinability are desirable wood characteristics for window work. Certain species of wood were commonly used in different regions:
· Eastern White Pine in New England
· Cyprus and Longleaf Pine in the South
· Northern White Pine in the Upper Midwest
· Douglas Fir in the Northwest
· Redwood in California
Today any species can be shipped in from any region and imported from many countries, however local species may be more suitable, more readily available, more sustainable and less costly.

Cut and Selection

Using a good cut and selection can be more important than which species is used.
Vertical-grain and rift-grain cuttings may be more stable than flat-grain cuttings. Vertical-grain and rift-grain cuttings can be cut off the outer edges of wider flat-sawn planks and boards.
A piece of wood that is all heartwood is more decay resistant and more stable when the moisture content changes. This is generally true for all species. All-heartwood lumber is costly. If there are not enough funds or wood to select for all-heartwood, cuttings for sills and lower rails can be selected from the heartwood end of the board. Then the sapwood can be used in the frame headers and top sash rails. If a jamb or stile is only half heartwood, it can be set with the heartwood at the bottom where it will do the
most good. This is the way to "cut and select" for heartwood. Often there is a lot more heartwood in lower grades, so smaller cuttings can be taken from the clear wood between the knots.

Salvaged Wood
Wood from a damaged window part can often be saved and used to repair another window. Old growth wood salvaged from old buildings can be used in window preservation work. However, when a lot of salvaged wood is needed we must be careful not to develop such a demand for old wood that it accelerates the rate of salvage and the demolition of useful old buildings.

Wood-like Products
There are many contemporary construction products that imitate real solid wood, such as:
· Finger-jointed wood
· Composites of petro-chemical plastics and sawdust
· Polyvinyl chloride (PVC) plastic embossed with a wood-grain texture
· Fiberglass
· Polycarbonate plastic
These wood-like products are not used in window preservation as substitutes for real solid wood.

KenN
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Re: Wood

Postby KenN » Fri Mar 08, 2019 10:05 pm

Is there any reason white oak is not used for window sashes? I have seen it used for sills but not for other sections of the frames or for sashes.

I hope to make some non-moving(casement?) sashes this year and I was thinking for longevity outdoors why not white oak?

johnleeke
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Re: Wood

Postby johnleeke » Fri Apr 19, 2019 8:08 pm

White oak is fine for window sash. The heartwood is quite decay resistant. I have seen 300 year old sash made out of it.
It's not common because other woods (like pine, cypress or fir) are less costly and more easily worked and machined.


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