Saturday, April 11, 2009

Old Growth Timber

Old growth timber is one of those terms you run across on occasion but almost never hear defined. For the cabinet maker and timber frame carpenter old growth timber is the ideal medium for strong and stable furniture and framing. But what exactly is old growth timber?

Once upon a time in the forest primeval white pine and other trees grew close together in dense stands of timber. Since light was scarce under the thick canopy of leaves and pine boughs, young trees grew slowly but very straight as they strove to reach the sunlight far above them. Since there wasn’t much light near the ground, trees expended little energy growing branches and leaves low on their trunks. As a result the trunks of old growth trees were not covered with knots and produced clear lumber when milled.

The slow growth means growth rings were very thin, so the wood is very dense and stable. Another product of slow growth was a much higher percentage of fine heartwood. White pine was especially straight grained with little wane (i.e. the natural taper to a tree trunk) because the trees grew straight up to reach the sunlight of the canopy above.

In comparison to lumber sawn from true old growth timber, lumber today less dense, straight grained and much more liable to twist and warp. Below is a cross section of the sill from an 1882 depot from Chaksa, MN. This example has up to 20 growth rings per inch and is quite heavy and dense. Much pine harvested today has around 6 to 10 rings per inch and is far less dense in comparison. Anyone who has sorted through a pile of twisted, wracked and warped lumber at a lumberyard or supplier can appreciate the qualities of the old growth timber. It is little wonder that even some the most hastily built furniture from the 19th century survives with so little warping, splitting and decay.

Since virtually all of the old growth timber was harvested in the eastern U.S. and most of the remainder is now protected, old growth is now salvaged from building demolitions and remodels. A fair amount is also being recovered from lake and river bottoms where logs sank during the 19th century. Unlike the 19th century, when it was used for the most mundane purposes, old growth is scarce and expensive and used only for special projects.

Sunday, April 5, 2009

Something Completely Different

Since it is old and it is a house (of a sort) I am featuring one of my favorite buildings in my latest post on the Old House Blog. The Peterson, IA blockhouse is one of those architectural surprises you can find in many small towns across the country. Built in 1862 from hewn logs, this structure is an extremely rare example of a wooden military fortification from the upper Midwest.

First, a bit of history. Relations between the native Dakota Indians and white settlers in Iowa and southern Minnesota were extremely poor after years of tension and occasional violence. Armed conflict, including the Spirit Lake Massacre of 1857 and the Dakota War of 1862, and the absence of federal troops due to the Civil War led Iowa governor Samuel Kirkwood to form the volunteer Northern Border Brigade in 1862. As a part of this defensive scheme, a series of fortified blockhouses were constructed near white settlements such as Correctionville, Cherokee, Peterson, Estherville, and Chain Lakes, IA. Each was to be garrisoned by members of the Northern Border Brigade militia. However, the need for protection had diminished greatly after the rout of the Dakota in the Dakota Territory by Union troops in September 1863 and the forced resettlement of most of the Dakota remaining in Minnesota after the Dakota War. The garrisons were deemed unnecessary and the Northern Border Brigade was disbanded by the Iowa adjutant general in 1864. The blockhouse, which had been garrisoned by as many as two dozen soldiers, was abandoned sometime between 1865 and 1866 by the few, remaining federal troops.

The Peterson blockhouse was constructed by members of the brigade using locally harvested and hewn 10” oak and ash logs. The structure was surrounded by a stockade which provided protection for the garrison, its horses and supplies. Rather than a typical stockade made from a series of upright, pointed logs, the garrison constructed a fence made from massive, sawn oak planks and hewn oak and ash timbers that were as thick as 6”. Both the upper and lower levels were equipped with small, defensive gunports. The structure was built using square, lapped (and most likely pinned) joints rather than the more common half-dovetail or square-notch. The building was originally roofed with joined maple planks with grooves to lead away rain water.

After its abandonment the timber from the stockade was removed by settlers and used to construct other buildings while the blockhouse itself was dismantled and reassembled on a farm two miles west of Peterson. In 1977 Peterson Heritage acquired the building and moved it back to town. Although its original location was unknown, Peterson Heritage rebuilt it at the most likely spot, in the boulevard on Park Street just south of the intersection with Highway 10. In the mid 1980s volunteers restored the structure (without a stockade) using the original plans, replaced several logs and put the building on a concrete foundation. The restored building was dedicated in 1986.

The blockhouse can be visited anytime, but is open for visits during Peterson's heritage celebration held on even numbered years.