Timber Frame Design
There are many other aspects of design to consider for both interiors and exteriors. The decision about the exterior style is probably the easiest. Your timber frame will be wholly inside the walls of your house, whether you enclose it with stress skin panels or in some other manner. Consequently, you can use wood, brick, stucco, stone, or any other exterior that will fit your setting, whether urban or rural. You may want to transfer the timber frame style to the exterior in a porch or other decorative detail. The timber framed posts and trusses add a striking accent to masonry as well as to wood.
Envision your timber frame home on the site so that you can what style suits it best. Also consider the best location for various rooms in terms of the view from your windows and where the sun will be positioned throughout the day. A topographical map of your site will be helpful.
You will find many beautiful pictures of timber frame interiors and sample floor plans in the magazines and books. Choose some that particularly appeal to you and keep them nearby as you begin working on floor plan ideas for your house. Think through how much living space you will need, and how you want it organized within the structure. Allow yourself to dream at this point. This will enhance your creativity. All you need is a rough sketch of each floor. Free hand is fine.
While these ideas are perking in your mind, this is a good time to talk to the building inspector in the county where your home is to be built. You may have talked with him already about a septic permit and requirements for a building permit.
The Next Steps
Now you’re ready to start talking with one or more timber frame companies. Most companies will confer with you based upon your floor plan sketches and the pictures you’ve selected. They can give you advice on how to accommodate the style you prefer to the structural requirements of your floor plan. In addition, they should be able to help you find ways to get the best timber frame for the style and size you require. At this point, they also should be able to give you a ballpark estimate on the cost of the timber frame you’re considering. You will also need to talk with them at this point about how you intend to enclose your timber frame.
If the timber frame company has stock home plans, it may be wise to look at them to see if any are close to what you are looking for. These timber frame home plans are already designed and engineered, potentially saving you a considerable amount of money in design fees. You’ll also save time as a custom design will typically take three-to-four months. Keep in mind that the floor plan in standard timber frames can be altered to suit your needs. The only things you can’t move are the posts! (Well, you can move those too, but it takes re-engineering and re-design.)
Once you have defined the frame and enclosure you want, the timber frame company should be able to give you a firm price. At that point, a sales agreement can be drawn up and signed. Then, within the time frame agreed upon with the company, the preliminary design phase, which includes floor plans and elevations, will begin. These will be revised with your input, until you are satisfied that the use of space and the style of the timber frame met your wishes. Next, the designer begins to engineer the frame, calculating loads and stresses to determine the size of timbers and kind of joinery required. This will result in your final drawings, or blue prints, which will be sent to a structural engineer, if required. This person will require any revisions he or she finds necessary, based upon the code requirements for snow and wind loads etc. in your locale. These will be presented to you, along with any costs for the change and, with your approval Goshen's designer will make the changes in the blueprints.
Timber Frame Wood and Finishes
One of the first decisions you will make when you begin designing a timber frame home is what wood to use. The most commonly used woods are eastern white pine, douglas fir, and oak. There are many structural and aesthetic factors involved. Oak timbers are darker and heavier than pine. They also are stronger, and may be smaller in size to carry comparable loads; however, they are less stable and consequently crack and twist more than pine.
Cypress wood is suggested for porches and exterior trim. Cypress is renowned for its durability. The heartwood in cypress trees produces oils that help resist decay when exposed to moisture. These oils also provide a natural deterrent to termites and other insects. While technically a softwood, cypress is extremely strong and is commonly used as a hardwood. The timbers have an attractive grain and a golden brown to reddish-brown hue. Cypress's excellent qualities are beginning to recommend it to our customers for the main, interior frame as well as exterior porches and trim. Its cost is comparable to douglas fir.
The cracks are called "checks" and will occur in all large timbers. Very rarely do they cause structural weakness if the proper grade of timbers has been chosen for each application. Many people view them as adding character to the frame, especially since checks are a feature of antique structures.
While many companies allow the timbers to season for five to six weeks, essentially they are cut green. Once locked into the frame, however, the tension prevents some of the twisting and checking. It is advisable to avoid drying out the frame too rapidly at first, especially during the winter heating season. If you make an effort to keep the heat down your first winter and keep a humidifier going, you will be able to reduce the degree of checking.
Grading Timbers
Building departments typically require that the frame design drawings indicate the grade of timbers to be used in the frame and that the actual timbers be stamped to certify that they meet the grade specified. There is a very good reason for this requirement.
As we know, different wood species have different strengths. This is also true of specific timbers cut from one species. Various conditions, such as the number and size of knots in the timber, fungal rots that may be present in the wood, or breaks in the wood fiber may reduce the strength of the timber. For this reason, each individual timber must be inspected and graded for structural strength.
When the designer does the structural engineering for a frame, he or she selects the grade required to ensure adequate strength for the loads on that member. These design values are established in the American Society for Testing and Materials' standards. In most cases, the designer has the option of using a higher grade of timber or going to a larger timber for a specific member in the frame.
Blue Stain
Certain types of wood get a fungus called "Blue Stain." White pine, which is used extensively in timber framing, is one of them. The fungus that causes Blue Stain begins to grow as soon as the tree is felled and feeds on the sap when the wood is moist. Consequently it affects the sapwood, working inward through the log or timber, but stops at the heartwood.
Blue Stain is not destructive to the wood and will not cause rot or structural damage. In fact, blue-stained wood is used for cabinets because it is considered by many to be attractive. These people are willing to pay a premium for it. A high proportion of timber frame owners also enjoy the blue striations in the timber frame, as it gives it more character.
However, if you do not like the look of Blue Stain, talk with your timber framer about ways to control or eliminate it. They include using winter-cut timbers, which are not as susceptible because the sap is down; or dipping the timbers in a fungus-killing chemical, which will retard it for a while. Keeping them well-aired while stacked will also help. Scrubbing the timbers with a bleach mixture can reduce the visibility of the Blue Stain. Once the timber frame is erected and the timbers are in a lower humidity indoor environment, the Blue Stain will stop spreading. |
