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Timber Frame Addition

Nailing the ridgepole	Timber Frame additions to the main house and pantry

 

In 1981, we had to make the same decision that many homeowners have had to make. Our family was increasing and we needed more room. Do we move to a bigger house or add on? Actually, for us the choice was not difficult as we loved our home and had the room to build an addition. A number of questions still had to be answered:

Size: we needed another bedroom, a dining room, a den and a larger pantry.

Where: the back of the house had a kitchen ell on the left side. If we filled in part of the remaining space, the new foundation would measure 20' deeper towards the back, and 26' wide. While it was possible to build to the left of the house, the symmetry of the Cape Cod style house would be lost. From the street, our home looked small and we wanted to keep it that way. By tearing down the rear porch, the pantry at the end of the ell could be increased toward the first stone terrace wall by another 6' and still leave room for a the rear walkway.

Floors: the first floor of the addition could form two rooms, a bedroom and a dining room. The roof of the second floor den would have cathedral ceilings and slope down to the same eaves as the original structure which for Cape Cod style houses is formed by a knee-wall.

Style: While stripping aluminum siding off of our house, we found out that the style of the house was Greek Revival. Greek Revival is described in a separate link . For me, it was important to keep faithful to the original style when doing the additions. The original wide side moldings, box cornices and returns on the main section proved to be complicated to copy but made the addition appear as if part of the original house.

Method: Having for many years enjoyed the challenge of making furniture using traditional methods of joinery, I had always wanted to build a timber frame. After purchasing the house I soon discovered that even in the 1850's and 60's timber framed houses were still being built. By that time, however, all the framing was hidden and the roofs were being framed in the modern style of rafters common today. In designing the additions, I chose the timber framing methods of the 1700's including exposed gunstock posts, summer beams and a roof framed using purlins with principal rafters.

Research: In the early 1980's post and beam (timber frame) construction was starting to become popular after a hiatus of over 100 years of balloon construction. A number of books had come out including some by Stewart Elliott. Now, there are many more to choose from which also include the tables for beam load for various types of wood. As I did not have these, it was necessary to use the formulas for each beam.

Prior to Removal of One Garage and Rear Porch	Drawing Showing the Rear Elevation

After reading the above mentioned books and studying old houses in the area as well as at Old Sturbridge Village Living History Museum in Sturbridge, Massachusetts, I began the drawings for the basement, the 1st and 2nd floors, end and side views, roof structure, etc. Before I drew out a post or beam, it was necessary, as mentioned earlier, to know the load on each piece and then use the formulas for beam load.

The formula included the type of wood, the length or span of the desired beam, and the thickness (horizontal) and depth (vertical). From my drawings, I knew the span and thickness needed. The variable was the depth. Depth could vary without affecting the thickness of a wall. The rule of thumb is that the center of the span of a beam can safely drop 1/360th of it's length. Suppose a New England yellow pine beam with a thickness of 6" had a span of 360", what depth of beam would allow it to drop no more than 1"? If I wanted a depth of 7" and the formula resulted in a drop of 1.5" - no good! Now I try a 9" depth which results in a drop of only .25" - the beam would be heavier than needed. Now I try 7" resulting in a drop of only .75" - then my beam will be 360" by 6" thick by 7" deep. This is obviously an absurd example as such a beam would be 30' long and is only for the purpose of understanding beam flexing. However, as I have said, now books (such as those written by Tedd Benson) on timber framing come with tables for most beam sizes and types of wood.

Drawings of individual beams

An important goal was to present the building inspector with enough accurate information that he would issue a permit without my having to hire an architect to review my drawings and sign off on them. I presented him with all the drawings, all my calculations for beam load and the resources I used to obtain my results. A few days later he approved the plans with only one change. He required a second lolly column in the basement. This was fine with me

As I had never done a timber frame construction before, it was necessary for me to actually draw out each of the beams to scale in exact detail. Although we would have help from friends in raising the structure, only my wife, my 14 year old son and I would be moving the heavy beams around during the eight week period when we would be making the joints. It was impossible to try out the finished joints before the "house raising" so all the joints had to be accurate with no opportunity to pretest them.

I found a man in southern New Hampshire who would cut down the trees for the beams and sheathing, take them to a friend with a saw mill and have them cut to my specifications. In this way, I wasn't restricted to standard sizes. For example, the first floor plates were 7" deep as determined by the formulas. When he arrived with the first load of beams, their size and weight (green wood) suddenly hit me. How was I going to move these beams around without help? This 'old Yankee' simply said "You move them with your brain and not with your brawn". He proceeded to show me ways of moving and lifting the beams using leverage, balance and rollers.

At this time, I should explain that in sheathing and flooring, the wood needs to be well dried as wood shrinks in width and thickness but not in length. Because width is critical in boards they must be dry before being installed or spaces will result between the boards. For beams and posts, only the length is critical and they can be installed green. Splits will occur in the beams but this does not affect the strength of the beam as the splits follow the direction of the grain.

In late winter, we tore down one of the garages (the one that would partially occupy the space of the future main addition) and an old porch at the rear of the ell where the enlarged pantry would be.

 

We were worried that ledge would be found when digging the foundations. A small backhoe was brought in and soft ledge was found under the future pantry and was removed. Because I had to pay for a whole truck of cement, use it all or not, I suggested pouring a complete floor when pouring the footing at the required 4' depth for the pantry foundation. With a trapdoor into the pantry, the space formed became an excellent storage area for my wife's preserves and grains. It remains at 35 to 40 degrees all winter and never freezes.

The small backhoe did fine digging the basement space under the main addition until it hit a big rock. A larger backhoe had to be brought in which dug all around the boulder and found that it continued under the kitchen in the ell! As it was important that I have a full basement for my future shop, we decided to have it removed up to the kitchen foundation. The blasting was an unexpected cost which delayed the finishing of the interior for a few years.

Drilling prior to blasting the glacial boulder	Framing First Floor Over Concrete Foundation

While the foundations were being dug and poured during the spring, we worked on the joinery for the first floor beams. With a friend, I assembled the beams and sub floor. We also spread the gravel for the basement floor and around the outside of the basement footing. Within the gravel, we placed perforated drainage pipes as we live at the bottom of a terraced hill. A 4" concrete floor was poured in the basement. We applied tar and backfilled the foundation to make the area safe for the future work. Once the basement had been framed and covered with a sub floor, I invited my wife to step out from the kitchen into what would become the dining room. She immediately said that she wanted the 20' by 26' area to be one large room rather than closing off the further end as a bedroom! So we decided to make the front parlor into the needed bedroom and the first floor of the addition into a parlor-dining room with no wall in between. As it is the posts that support timber framed structures, not walls, the only adjustments to my drawings were to erase the wall and make the center post fancy by changing to a 6" x 10" and shaping it into a double gunstock.

The above mentioned book had a design for extra strong saw horses of which I made four before doing anything else. These tall and sturdy horses held the beams while working on them and served as safe platforms for us to stand on when lifting beams to upper levels.

The next six weeks were spent working on the beams with the pantry ones completed first. I then assembled those as practice for the main house raising. All exposed beams (gunstock posts and ceiling beams) had to be hand planed which my wife soon learned to do.

Mortising with Chisel and Mallet	Invitation to Assist in the House Raising

Following the scaled drawings for each beam, I then lay out the joints. Using the circular saw, I made the side cuts and drilled out the back ends of mortises. Using a framing chisel, corner chisel, mortise chisel and two sizes of mallets, I finished off the joints. My wife often helped on the chiseling when she had time between planing. At times, an antique ship builder's adz was needed to quickly remove material as when changing the lower part of a 6" x 8" column to a 6" x 6" column when making a gunstock post. A drawknife and smaller planes were used to do chamfering.

Traditionally, coins (silver dollars) were placed under each column

As the beams were finished, they were marked with the same code as on the drawings. They were then rolled from the work yard on the left side of the house to the side where the addition was to be assembled. For this, a miniature railroad was built consisting of a rail of planks and wheels of made of short pipes. I would push the beam, my son would pick up and reposition the rollers, and our young nephew, (eight years old), would act as engineer sitting on the front. His other job was to keep us supplied with water. Our daughter and a niece, (both also eight years of age), had the task of cleaning all the shavings and sawdust and transporting them to the compost pile. The piles of beams were arranged in such a way that the ones on the top would be the first ones required on house raising day .A month before the house raising, a letter was sent out to our friends asking them to join us for an old fashioned house raising party. As the day approached, we had to work quickly and efficiently to have all the beams ready because we could not change the date. The day before, I made all the mortises into the previously assembled first floor to receive the tenons located at the bottom of the gunstock posts. I did not have time to remove the aluminum and clapboard siding which would be necessary before the raising.

My wife made up a lot of food and snacks and we made sure we had plenty of beverages (but no liquor until the raising was over). The pantry addition became a refreshment area and first aid station. Tradition says that the workers (including two women) come early and the families later. The families each bring a main dish or desert. We would supply other food, liquid refreshment and 2" steaks.When our friends arrived, I talked with them about working safely, teamwork and proper ways to lift the beams. I calculated that the summer beams (8" x 12") weighed over 600 pounds as they and all the other beams were still full of water (green).

Lining Up Column Tenon with Mortise	Lifting the Summer Beam

The first step was to remove all the siding which I hadn't had time to do and which took almost three hours. We then set all the posts in place and temporally braced them. At this time we had a brief ceremony as we placed coins into the mortises that the tenons on the bottoms of the posts would fit into. We obtained seven bicentennial silver dollars plus three coins from my wife's country of birth. The bicentennial coins were appropriate as we purchased the house in 1976. The coins are supposed to bring prosperity to those living in the home.We became quite efficient with teams joining the beams, a person drilling the holes for the trenails, another pounding the trenails in and another cutting the ends off. My son previously took the hexagon shaped oak rods I had made, cut them to length, sharpened an end and cut barbs into them so they wouldn't back out once pounded into their holes. Two sizes were made, 3/4" Dia. x 6" and 1" Dia. x 8". The work proceeded swiftly, except when some of the joints needed friendly 'persuasion' with a come-along or sledge hammer. To work on the second story, we placed planks over the first floor ceiling beams in order to walk on, made ramps from other planks to slide the remaining beams up and made platforms using the sawhorses. I cautioned everyone to be extra careful as we were working from a dangerous height now. It took almost six hours to raise the structure after which we had another ceremony. I nailed a pine branch to the highest point on the frame and did the 'blessing' of the addition with a bottle of homemade wine.

Teamwork	Closing Ceremony with Homemade Wine and Pine Bough

As all the families had by now arrived and were watching from the terrace behind the house, we had an enthusiastic audience. Now the steaks were ready, our friends had brought the dishes they had made and we had a great meal! My wife and I went around thanking everyone for their help and many commented that they appreciated having the opportunity to experience something they had read about but never seen before. Without our friends, we could never have accomplished our goal of building a timber frame. A few friends came back to help me sheath the frame with tongue and groove boards and cover all with tar paper to keep the water out.

I did not use any plywood, wafer board (did it exist back then?), etc, as I believe the glues in these materials give off gasses which create an unhealthy atmosphere inside homes. The following year, I shingled the new roof and stripped and reshingled the old roof. Then I copied the previously mentioned trim on the addition, applied red cedar shingles as siding, stripped off two layers of siding from the original house (earlier wood and later aluminum) and placed the cedar shingles there also. The red cedar shingles do not need paint or preservatives as red cedar has natural preservatives. That way, all I need to paint is the trim! By having only 5" of the shingles exposed, rather than 8" or more, all of the shingling is three layers thick making the wall, more waterproof and better insulated. Eventually, we completed the inside as explained in the link on woodworking.

Our Friends Enjoying a Meal after the Raising	At Dusk

 

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