Wednesday, May 8, 2013

Chapter 5 - The House Plan

Chapter 5 - The House Plan
  The plan for the house revolved around having everything that we needed on one floor. Since a square provides the most floor area with the least wall area, we settled on a 40 by 40-foot square house plan for economy. Bearing in mind that a square timber-framed building would define four square interior boxes, we arranged the kitchen, bedroom, dining room and living room, boxes within this floor area. The kitchen had to be the most accessible room with lots of sunshine. The bedroom had to be the least accessible and could be cooler since we both like lots of covers! Naturally, the western view of the mountains had to be the feature of the living room and dining room. We then decided that an appropriate average size for these four rooms would be about 16 by 16 feet. Therefore, a 32 by 32-foot box would work. However, the plan was missing a bathroom and a stairwell to the basement! So we added eight feet to both dimensions of the house to fit these very important features into the plan. This extra eight feet in both directions became a plus shaped space dividing the four main room boxes. The part of the plus between the bedroom and kitchen naturally became the bathroom. The south and west parts of the plus became entrance ways and the north part of the plus provided space for storage and a chimney. The center of the plus provided the central staircase area.
The four drawings on this page include a Deck Framing plan and three frame Bent drawings. The Deck Framing plan illustrates the timbers used to frame the deck as well as serve a a plan drawing. The left side of the drawing is north, the daylight basement opening side faces west at the bottom. The blue shaded area is the portion of the basement that was not enclosed and served as a workshop. The white area is the portion of the basement that was walled off to serve as the apartment. The three bent drawings are of Bent #1, Bent #2, and Bent #3. The Bent #4 drawing is the same as the Bent #1 drawing, the difference is that the basement wall is a solid concrete wall without any framing. In two dimensions, it is difficult to illustrate the Bay framing. My solution is to illustrate the bents with the joints for the Bay behind it showing. What does not show are the joists in Bays #1 and #3 which run north and south as they do in the Deck Framing plan.
 We were both accustomed to heating our homes with wood stoves, so a chimney also needed to be in the plan. Since an 8 by 16-foot area for storage is more than enough, a chimney could also occupy some of this part of the plan. The firewood available on our new lot however, is not the hardwood that we were accustomed to in Pennsylvania. We discovered that the wood-burning stove that is best adapted to the use of pine is called a masonry stove. After reading a book on masonry stoves, we decided that we would like to include one in our plan. The massive weight of this stove, not to mention a very tall chimney called for a thick foundation at its base. Having participated in erecting a timber-framed home that had not allowed for a pathway through the timbers for a chimney, I made sure that my frame plan left such a clear space from the foundation to the roof.
Having had the experience of a lot of snow where we planned to live, we decided that a steeply pitched roof to shed the snow load would be a good idea. This also produced a very large loft area providing extra space should other folks decide to help occupy our home. Having lived in an ancient home with numerous exterior additions made to it over the years, “the cave”, Linda wanted lots of windows and open space. We decided to leave the space over the living and dining room areas open and use the loft to provide a ceiling for the bedroom, bathroom and kitchen.
With all of our wants, wishes and desires accounted for; our house plan became a three-story tall-posted cape design. As we look back on the design and building process, we have often wondered if perhaps we might have gotten a bit carried away. This house is huge, considering there are only two occupants. We could have done without the loft, and experience has taught us that the steeply pitch roof is not necessarily the best idea. A roof pitch of 9/12 over a 40-foot span creates a substantial amount of loft living space, something the two of us really don’t need. However, this space is currently used for storage, something we definitely do need. As for the daylight basement, we still think it is a good idea. The finished daylight basement where we have lived for three years while finishing the main floor is cool in the summer and easy to heat in the winter. Room sizes could probably have been reduced to 14 by 14 feet without being too cramped. If we had it to do over, the house plan probably would be about 36 by 36 feet with a 6/12 pitch roof instead of the 40 by 40 feet with a 9/12 pitch roof that we have built.
What I wanted to build is a new building the old fashioned way. All of the new timber-framed buildings that I had worked on were built upon a modern deck. Somehow, TGIs and steel posts in the basement clashed with the timber-framed structure above it. When I asked Ed why the decking of these buildings was not timber-framed to match the building, the answer was cost. Most of this extra cost involved with timber-framed structures is in the labor. Since I proposed to provide the labor, I could rationalize that the labor costs for our plan was zero. This of course is pure rationalization, but it provided the excuse to design my building the way I wanted it.
Free spanning 40 feet across the basement would have required deck support timbers that would not only be unwieldy, but also be very hard to come by. Since the plan called for a central stairwell, I designed a central box to hold up the deck support timbers that radiated out to the foundation walls. This central box would also serve as the support for the stairwell from the basement to the first floor. This central box is duplicated on the first floor to house the stairwell that leads from the first floor to the loft. Again, this central box serves as the support for the framing that extends outward to the exterior walls. This central box became not only the central support and attachment structure of the frame, but a central architectural feature of the house. This plan insured that no timber needed to be longer than 16 feet.
I used nine 8x10 and 10x10 posts to create the center support box in the basement. This is certainly overkill, but it gives a visual impression that the frame is anchored and supported substantially. These nine posts are on 4-foot centers providing plenty of room between them for central passageways, stairways and landings. The nine first floor posts standing atop these nine basement posts are 8x8s in keeping with the dimensions of the rest of the frame. Since the decking beams sit on top of the10x10 basement posts, their top surface area also provides plenty of room for the 8x10 deck beams to be joined and rest safely on top of them.
The daylight basement opening also needed to be framed. The original idea was to use the basement as a garage, large doors on either side of an 8-foot central entrance. This 8-foot central entrance, like the central box, served to support the large spans for the garage doorways.
I wanted to use rafters and purlins for the roof structure just because I like the look of this system. In order to avoid joining the bent and bay horizontal frame beams and the rafters all at the same point at the top of a post, I decided on a tall-posted cape style frame. This separates the horizontal beam joinery from the rafter joinery by the height of the tall post. I read warnings about the stress placed on the top part of these tall posts by the rafters. With this in mind, I designed the tall posts to be 2 feet tall, only 14 inches above the top edge of the horizontal frame beams. The other purpose of taller posts is to create a knee wall at the outside edge of the house at the loft level, increasing the usable area of a loft. With a 40-foot span, we did not need tall loft knee walls at the edge of the frame to increase the loft’s usable area.
I also wanted a ridge beam and king post roofing system, again because of the appearance. The geometry of a 9/12 pitched roof and a 40-foot span reveals the rafters to be 25 feet long. Again, timbers this size would be unwieldy and hard to come by. Since the frame posts are 16 feet apart, I duplicated this dimension for queen posts and also duplicated the 10-foot tall frame posts to serve as attachment points for the rafters. This reduced the 25-foot rafter span basically in half to a more manageable 12 feet.
To help bear some of the roof load, I also added stub posts under the rafter ends, three feet from the end connection points of the rafters to the posts. Theoretically, these stub posts transfer some of the roof load on the top of the posts to the center of the posts via the first floor braces.
The problem with the central box idea and the goal to maintain a flat flooring surface in all four directions is that all of the beams meet the posts of the central box at the same point on each side of the posts. The top of the post gets riddled with mortises and once two of the beams are pegged, the first two beams cover the peg site of the other two beams. In the basement, I solved this problem by using beams long enough to span to the center post and used a large scarf joint. This created a 40-foot level span across the basement with the scarf joint resting on the posts in the center of the box. These timbers had to be about 22 feet long. Keith was having trouble finding large enough oak trees to produce 22-foot long 8x10 beams. The eight that I used for the basement decking was all that I could get. Since I wanted to produce a level floor at the loft level as well, I needed a new technique.
Diverting from traditional framing techniques, I borrowed a spline technique from Ed. I did not find the spline technique in any of the timber-framing books that I had read. Traditional joinery does not allow for beams at right angles to each other to be joined at the same level without using very large timbers. Since I wanted the frame to have a level surface at the loft (or first floor ceiling) level, splines seemed to be the answer. Additionally, since my intention was to raise the frame by myself and without the aid of a crane, I needed a joinery method that would allow assembly on a timber-by-timber, one at a time basis. Extensive use of spline joinery solved both of these problems. Essentially, the tenons for the beams are replaced with 30-inch long 1 1/2 by 4-inch splines that pass through the post. These splines are 30 inches long to accommodate two pegs on each side of the post without splitting the spline.

No comments:

Post a Comment