Structural TimberEssay Preview: Structural TimberReport this essayIntroduction:In my report I will discuss the historical and environmental element of timber as a structural frame. As our awareness of our carbon footprint increases so does societies need to be more sustainable. Timber has been around since the beginning of time; it has low embodied energy and absorbs carbon, reducing the environmental impact it has on the earth, thus being one of the most rated building materials.
Historical:Wood is a natural product because it comes from trees. Different trees and different parts of trees produce different types of woods, for example coniferous trees produce softwoods and broad-leafed trees produce hardwoods. Wood must go through many processes before it can be made into a timber frame, some of which include sawing, seasoning and grading. The first timber framed buildings were pit houses, lean-tos and teepees.
Figure 1: Pit houseFigure 2: Lean- to Figure 3: Teepee(Source: Google Images)In the middle ages the first braced wall frame of timber was built. This was known as heavy wood framed construction. Since then braced wall frames were very popular and one of the only methods used. When the british carpenters imigrated to North America in the 17th and 18th centuries they were able to share their knowlenge of braced wall frames with the North Americans. They then proceeded to work on buildings framed with hand- hewn wood pieces, which are pieces of wood cut or shaped with hard blows of a heavy cutting instrument like an axe, joined by interlocking wood to wood connections. This was because nails were rare and expensive so they could only be used for door and window constructions.
British architects in the Middle Ages are known to have had various ideas on how to construct the brick wallframe. However the first attempt to produce a strong wall frame was made in 1639. This project led to a combination of architectural techniques, such as doubletension to the front frame which required a combination of two angles of the wall between the top and bottom of the frame. This worked as it helped shape the frame which was the key to building a strong wall frame.The original wooden brick of Saint Anne’s Cathedral in Saint Paul, Belgium was about 30 cm x 24 cm, although the finished frame cost only a few hundred dollars. It took several years to complete this project which became known as the Braced Wall Frame. Its construction involved the most expensive piece, probably a piece of clay, which was used to build a pillar. However it was done in the year 1660 and completed in the last 150 years. To make a “bronze” wall frame after a heavy block was cast, the builders usually have to make a piece of wood or clay. The “bronze” block was put away at the start of construction and the timber frame was filled in. A wooden bench to keep the rest of the frame cool until the block was finally built was erected around it.After the original brick was constructed, it must be reinforced with steel to keep the frame strong enough to be able to withstand a few days in the snow. In the process of building a Wall Frame the work was painstakingly arranged, the only exception being the two “wall frames” used and the “bronze” frame. The walls in which the brick is made are built as if it had been struck down one by one, in order to avoid the construction getting stuck in the snow and it would not survive the impact on the floor. The construction of the wall frame is carried out by placing it on the wall, holding it there a bit longer than the other two. Before making the wall frame a number of small windows should be put to help it stand upright. When the workman moves the windows at the corner to prevent people from noticing they’re closing and turning upside down, the window is locked up. The same process can be followed to make the wooden wall frame. By holding a wooden table and other things at the end of the frame, it takes a little bit of energy to make the framing. The frames can be built for up to 30 years. The Wall Wall Decagonal Frame was made of 10% oak oak in the shape of a castle, by a Dutch contractor known as the Duke of Ghent. This was of considerable use in Denmark in the second millennium B.C. However it was also used as a decoration for the walls and it was only carried on by Dutch men. It served in the military until the seventies following the German occupation in which it was used in the defense against the German invasion. It wasn’t until World War II that the wooden wall frame was seen again. This new piece of wood was used in the
Figure 4: interlocking hand hewn wood (Source: Google images)In the 19th century builders realised that the heavy posts of the frame could be removed due to the closely spaced vertical pieces of wood used to fill the walls of the heavy timber frame were strong enough by themselves. This is called light wood frame construction and was only accomplished due to boards, smaller pieces of wood and nails becoming inexpensive and more accessible. The earliest light wood framed construction is the balloon frame, which used full length studs that ran from the foundation to the roof but this was too hard to put upright. Several more frames were developed including the universal standard platform frame. This is constructed by elevating the walls on top of a floor platform, this is repeated if there is a second story and the roof is then built upon the set of wall. Different variations of the platform frame are available to account for the number of stories in the house, to include attics and to even incorporate the use of a concrete slab foundation. Timber structures are an increasingly growing option all around the world; it is well known for its accessibility, cheapness and sustainability factor.
Environmental:Buildings account for 30 to 40 precent of the worlds energy use and associated greenhouse gas emissions (The U.S Green Building Council 2008). To be sustainable, that is to meet the needs of the current generation without compromising the needs of the future generations; we need reduce the amount of energy expended by buildings through design and construction. This is why timber is the perfect building material because not only is it strong so it will last for thousands of years but it is renewable and uses less energy than other materials such as brick, concrete or steel. The table below represents the embodied energy in construction and maintaining buildings with different wall materials. The examples with a timber frame use much less energy than other building materials not only for completing the construction but also after forty years of maintenance.
Type of ConstructionEnergy per unit area of assembly (MJ/m2)Energy used to complete construction (MJ)Energy used in maintenance over 40 years (MJ)Timber frame, timber clad, painted3102024750Timber frame, brick veneer, unpainted92565Double