Wood as a Material for Window Work (final)

Basic materials, Products, Generic Descriptions.
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Wood as a Material for Window Work (final)

Postby johnleeke » November 18th, 2011, 4:36 pm

Wood as a Material for Windows


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

The age and character of wood can often be determined by examining the end of the board or plank. Oldgrowth
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.
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 riftgrain
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.

Jim Derby
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Re: Introduction to Wood

Postby Jim Derby » February 1st, 2012, 2:19 pm

Hi Everyone;

I wanted to point out some differences between 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 their is a higher ratio of latewood to earlywood which in turn makes the wood stiffer, stronger, more rot resistant and hold nails better.

Today, forestry practices are to grow wood as quickly as possible by thinning forests and the climate is warmer than 200+ years ago thus also accelerating growth. I do not know the exact science why dense, slow growth wood is more rot resistant, but I see it all the time in old buildings. Of course the species affects the rot resistance and other qualities too.

New slow growth wood is rare to find today so it may be fair to say all new wood will behave differently than the wood used in our historic buildings.

I know a preservation architect who strongly feels that reproduction windows should be made with naturally rot resistant wood, even if it is not historically correct such as being a tropical hardwood, so the wood windows will be durable. I agree with this deviation from preservation standards. I have seen replacement sash rot out in less than 20 years and this gives ammunition to the window replacement industry among other problems.

Salvaged wood is likely old growth wood. We need to be careful not to develop such a demand for old wood that it accelerates the rate of salvage (demolition) of old buildings, otherwise known as mining the urban forest. The study of American historic carpentry is still in it's childhood and we need as many buildings to survive as long as possible just from the aspect of studying them.

Thanks for doing so much to save old windows!

Jim Derby

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Re: Introduction to Wood

Postby johnleeke » February 1st, 2012, 5:11 pm

Jim, welcome to the Window Standards collaborative. Thank you for your comments about wood.

That's an interesting point about the extensive use of salvaged wood promoting the destruction of old buildings. I wonder if the wood salvage companies have set up a certification program as has been developed for the sustainable harvest of rain forest hardwoods.
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Re: Wood as a Material (rough draft)

Postby peter_carroll » March 8th, 2012, 2:09 pm

Jim's reply is right on. "the qualities of the wood" in old windows & sash should be referenced often.

If plantation wood is used we should think heavily on how to choose pieces (heartwood vs sapwood, quarter sawn vs plane sawn) & how best to protect them from rot. (especially those end grains) Lately, I've been given allot of thought to new building techniques of storm sash that minimize end grain exposure, like pocket mortise & tenon joinery or free M&T. Also new wood is lighter & sash counterbalancing will be affected.

I took a piece of old growth fir and compared it to a similar size piece of Ipe and felt from a purely subjective point of view for them to have similar qualities. (density, durability, grain) The cost between Doug Fir & Ipe locally was not as much as I though it was going to be. Everything else being the same (maybe have to sharpen the blades more often with Ipe) it might make sense to upgrade species for sash & repairs when historical accuracy is not prevailing.

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Re: Wood as a Material (rough draft)

Postby oculus » March 8th, 2012, 4:53 pm

I have often wondered about upgrading species as well. My hesitation has always been about the different expansion/contraction between the two species when exposed to moisture. And how that would effect the repair. Might be an interesting experiment. I am also leery about where species like Ipe come from. As a tropical hardwood I would want to be very careful about who I am buying it from.
A question that comes up out here is whether to put a cedar piece in place of a rotted out Doug. Fir piece. A good example is a rotted out fir sill plate. Should another fir piece be put in (in-kind repair) or should a piece of cedar be used instead which gives a bit more rot resistance?
I don't have a good answer for it. We have much discussion with SHPO about it on a case by case basis.
Amy Harrington McAuley
Oculus Fine Carpentry, Inc.

"Opportunity is missed by most people because it is dressed in overalls and looks like work"-T.Edison

Bob Yapp
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Re: Wood Basics (rough draft)

Postby Bob Yapp » August 22nd, 2012, 2:31 pm

I tend to believe in using "In Kind" as a definition for replacing a wooden part or parts. To me this means the same species as well as similar age when first cut. I agree that we don't want to promote demolition for the sake of having old growth wood. However, I have two garages filled with old growth window sashes I have collected from window replacement contractors. The small amount of old growth wood I use to rehab historic structures and windows is only a recycling endeavor, not promoting demolition. I rarely have to replace window stiles and rails but when I do, it is important for similar contraction and expansion that I use "In Kind" wood to do so. I am opposed to using these exotic hardwoods from central and South America as most of this is causing the ruination of our rain forests as well as paint retention. Hardwoods do not, as a rule, hold paint well.

According to United States Department of Agriculture, Forest Service, Forest Products Laboratory, General Technical Report
FPL–GTR–190. Harwoods like walnut, oak etc are unsuitable for paint finishes. They list all cedars, white pines and true fir as the best woods to hold paint finishes for extended periods of time. Most sashe were made from eastern or western white pine. So, for durability and sustainability an in kind repair of an eastern white pine sash I would use either species of white pine of similar age (number of rings per inch).

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Re: Wood Basics (rough draft)

Postby hiles8500 » January 4th, 2014, 9:03 pm

I'm looking for wood sources in the DC suburbs for a storm window project. The big box stores and woodworking supply stores could not point me to sources of clear pine or doug fir. Old wood would be even better.

Before the recession, the Brass Knob Back Door had a great inventory of old windows that could have provided the stock. That was a great place. But they are gone now. Any pointers to good new and salvage sources would be much appreciated. I may try out Community Forklift in Hyattsville and Second Chance in Baltimore.

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