Valuable Information On Available Choices

• Post & Beam vs. Timber Framing
• Choices in Wood Species
• Surface Treatments Information
• Various Finishes Available
   

Post and Beam vs. Traditional Timber Framing

Traditional timber frames are designed and built with joinery much like fine furniture. Tenons (wooden tongues on timber ends) are inserted in receiving mortises (rectangular slots or pockets) and the joint is secured with tree nails (wooden pegs). Contemporary engineering standards may dictate the use of some metal fasteners, typically hidden within the timbers.

The terms “timber frame” and “post and beam” are used so interchangeably in contemporary conversation that we draw no meaningful line between them.

Wood Species Considerations ~

Just about every wood species that grows to a suitable girth and length has been used in timber framing. Our forefathers would typically have made good use of trees that were available, those often growing in the immediate area. With winter coming and a young family to house, one would have done the expedient. Here we we’ll discuss some of the advantages and challenges of commonly used species in today’s timber frames.

Green Oak
Oak has traditionally been used for centuries to build strong and durable structures. When a home is built with green oak it will take a period of some years for the timbers to dry. Once dry to the state known as that of “equilibrium moisture content” only seasonal change will occur thereafter. The rate which green oak dries depends on many factors such as the average relative humidity of the timber frame’s environment and the thickness of timbers under consideration.

You should expect oak timbers to shrink and check, which most folks find appealing. Checking can be minimized by adding humidity to dry winter air in your home and by keeping your thermostat set at lower and more energy efficient winter temperatures. We do our part to minimize checking by coating all cut end grain with wax (to stop drying and checking on timber ends and at joinery sites). We also build housings at major joinery sites to restrain movement and minimize gaps in drying timber joints.

Proper timber selection also plays a part in screening out timbers that exhibit tell tale traits of twisting as they dry. Oak, and all timber species for that matter, are natural materials and so change over time. Most likely you wear cotton even though it wrinkles. Polyester doesn’t wrinkle and it isn’t comfortable; it starts ugly and doesn’t improve. Cotton does its job comfortably and naturally – just like oak. We like oak best. You may, too.

White Pine
White Pine timbers are lighter in weight than oak and are not as strong. This is addressed by decreasing the spans covered, by increasing timber sizes, or both. The wood is readily available in long lengths, works well, and takes a fine finish. Joinery techniques can be used to compensate for the species relative weakness along the grain (spline joinery for example) and is locally available to us.

Cypress
Cypress is receiving ever more attention by timber framers. It is an excellent choice for outdoor structures because it is naturally rot resistant. Large sizes are available and it is pleasant to work. We will be seeing more of Cypress in the future.

Southern Yellow Pine
Yellow Pine is a stable and handsome wood, often available as reclaimed timbers. Reclaimed yellow pine, though expensive, is dry and so will only exhibit modest seasonal changes in dimension. If your budget permits, this wood is worthy of consideration.

Douglas Fir
Douglas Fir is a Western wood and is available in tremendous sizes and lengths. Its strength characteristics, combined with its availability in large sizes, often make it the wood of choice for very large structures. It can be had green, kiln dried, and as reclaimed timbers from demolished buildings. Its major draw back is cost to purchase and to transport. In our area, one must ask how much diesel fuel could be saved by leaving this Western wood in the West.

Other Woods
I have worked walnut, western red cedar, maple, gum, and redwood. I have examined timber frames of tulip poplar, spruce, hemlock, and redwood. All may have their place and can surely perform well. Should you happen to have a walnut timber laying around we can most likely find a good place for it in your timber frame.
 

Timber Surface Treatments and Finishes ~

Timber Surface Treatments
The first decision to make regarding the look of your finished timber frame is the texture of the timber surfaces. Here are some of your choices:

Smoothly Planed – This most common choice is the result of a portable planer, sharp blades, and patient technique. The timber framer sets the planer blade height to a minimum setting to minimize grain tear- out and planes each visible timber surface while advancing slowly. Areas around knots may require additional attention from a belt sander.

Wire Brushed – A somewhat more rustic appearance is achieved by using a portable machine that houses a spinning wire brush. The wire brush removes the softer early wood distinctly revealing the grain of the harder late wood. This finish is smooth to the touch yet lightly grooved along the grain – like an ocean boardwalk railing abraded by wind driven sand.

Hand Hewn – Best described under the heading, “How to make a timber framer wince”, this surface treatment is achieved by using an adze. The adze wielder chops along the length of the timber taking small divots of wood. The aim here is to replicate a timber that was produced by hand from the log.

Rough Sawn – Timbers are joined straight from the saw mill, saw marks and rough grain intact. Barns and sheds often display timbers that are rough sawn.

Timber Finishes
Throughout the past three decades of this ongoing timber frame revival, timber framers have tried just about every finish available. Some have worked well and some have failed miserably. The challenges are:

1. to find a finish solution that is easy to apply, readily available, and reasonably priced

2. safe to the user - the environment - and the occupant

3. durable and easy to repair

4. yields the desired surface appearance, and minimizes timber shrinkage and checking.

That’s a long list and most finishes do some of these things and a few do most of them.

Natural Oil Finish
These finishes are typically composed of tung oil, linseed oil, and a natural solvent such as citrus extracts. A natural oil finish is simple to apply with a foam pad, roller, or brush and is allowed to remain on the timber surface for up to one day, soaking into the grain. The resulting finish has a rich patina and the inevitable scuff marks are easily repaired by using an abrasive pad saturated with finish. While the finish is wet your home will smell like an orange juice factory, but the citrus odor dissipates in two or three days. These products are a good choice, yielding an adequate finish that is easily renewed and with no toxic substances introduced to you or your home.

In addition to standard natural oil finishes, some manufacturers offer oil finishes with wax that can be buffed to an incredible luster, with natural dyes for staining your timbers to desired color, and with mildecides for exterior use.

Petroleum Based Oil Finishes
Cheaper to purchase than natural oil finishes, petroleum based tung oil and linseed oil finishes have seen wide use. These finishes are a bit less forgiving in application as the excess should be wiped from the timber surface before becoming gummy. These finishes are right-off-the-shelf available and yield an attractive patina. Marred surfaces are easily patched. The big drawback has to do with the environment. The compounds are injurious to skin and lungs and saturated rags can combust. Most importantly, out gassing of harmful compounds can occur over a long period of time.

Varnishes and Urethanes
Applying finish to timbers in a timber frame differs from applying finish to a piece of fine furniture. The wood in the furniture is dry and pretty stable while the timbers are surely less stable and must be allowed to breathe while they dry (usually 4-6 years depending on the species). Urethanes and the like seal wood surfaces fostering mildew growth beneath the finish on green timbers and ultimately failing

Finish Application: In the shop or after raising?
Timber frame home owners are justly proud of their home. A good timber finish is critical to these discerning clients. Timber framers are constantly seeking the best solution to achieving an excellent finish. Some timber framers feel their frames should be shipped without finish, raised, enclosed and to then apply the finish. The one advantage to this approach can be a lower purchase price of the timber frame. The disadvantages include a somewhat greater risk of soiling timbers during shipping and raising combined with a lot of climbing later to apply finish.

Some timber framers apply finish to timbers in the shop. The advantage here is that much of the finishing is done with the timbers laying flat on saw horses rather than towering above you. The disadvantage is a small increase in the price of the timber frame and the realization that scuff marks will need attention after the frame is raised and enclosed.

As a timber framer I humbly admit that neither choice is perfect and that either approach can work very well with careful handling, a dry site, and no rain.

The Route to an Excellent Finish
There are a number of actions that both you and your timber framer can take to attain an excellent finish on your project. Your framer can protect the timbers from dust and the elements, with inside storage preferred. Timber bunks can be wrapped in timber wrap and edges protected with protective corners beneath strapping. The trucking company can be asked to tarp your load for transport. On the site, forklift forks can be kept clean or covered with a fabric cover. All timber bunks on the site should be blocked up off the ground and timber wrap should remain in place until timbers are needed for assembly. You should thoroughly straw your site to keep boots clean. Feet should stay off timbers during assembly. You could provide a hand washing station and ask the crew to wash up often. Finally you could pray that the rains hold off. The inevitable scuff marks are best addressed once the home is enclosed and you should have a clear understanding on who does this work.

If your earlier choice of finish was a natural oil finish, you may wish to reapply a coat after you have lived in your timber frame home for a year or so. This is a strenuous and potentially messy job and few choose to tackle it. Should you be so inclined, drape everything and wear eye protection. You will be amply rewarded with the effect.