Structural Use of Timber

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  • Topic: Building, Framing, Timber framing
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  • Published : October 25, 2012
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The Structural Use of Timber in Timber Framed Buildings|
Civil Engineering Construction 1|
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Adam Roberts|
13/12/2011|

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Table of Contents
The History of Timber Framed Construction1
Modern Timber Frame Construction2
Multi Storey Timber Frame Construction5
Benefits and Drawbacks of Timber Framed Construction7
References8

The History of Timber Framed Construction

Timber framed construction has been “used in Europe and Asia since the 9th century” (Wikipedia, 2011) . Timber framed construction was by far the most common method of construction in these continents due to the vast amount of timber that was readily available. Traditionally, the construction of timber framed buildings relied heavily upon pegged mortise and tenon joints, these joints were incredibly strong and are still used in traditional construction/renovation today (however glue is now applied to joint in order to give additional strength). The image opposite shows a completed pillar (under load) with two pegged mortise and tenon joints.

One of the earliest forms of timber frame construction was known as cruck construction, a cruck-frame consists of a pair of cuved timbers which are known as the cruck blades, these are often cut from the same tree by cutting right down the middle of the trunk, this means that whatever the shape (twist/bend) the pair will be identical. A collar/tie beam would sometimes be added in order to brace the frame and to stop it from bending/twisting. The cruck frame is the key element in cruck construction as the frame carries the whole load directly to the ground. “This type of construction continued until the early part of the 18th Century in the North of England” (Chiltern Open Air Museum, n.d.) as it was a tried and tested technique. Below is an image which demonstrates how a cruck frame building is constructed.

Modern Timber Frame Construction

There are currently two main (mainstream) methods of timber frame construction, these methods are known as pre-fabricated or “pre fab” panelling and stick framing. Pre-fabricated construction is fairly self-explanatory; this is when the panels are made to measure through a combination of automated machinery and manual labour in a factory environment (however it can be done on site if needs must), this means that the panels are ready to fit as soon as they reach the job site, this is done by simply bolting the panels together with traditional nuts and bolts. Stick framing is the complete opposite of “pre fab panelling” as this is when the frames are built on site using individual pieces of timber (known as sticks), it is generally considered that stick framing is the slower of the two processes and that the quality of workmanship can be lower if tight deadlines are in place. It is useful to note that both methods (done correctly) will end up with a finished product exactly the same in terms of look, feel and strength/durability. Below are two images which demonstrate the two methods. The left image displays a pre fab panel being hoisted into position, whereas the right image shows the skeletal structure of a building constructed using the stick frame method.

Now there are many structural uses for timber in a timber framed building, some examples include floor/ceiling joists, roof trusses and also the walls themselves. A relatively new concept in the construction industry is to use what is known as an “eco-joist”, now an eco-joist is a “composite joist which is comprises of a lattice frame, constructed from a pair of parallel and opposing stress graded timbers which are separated and jointed with a web of V shape galvanised steel plates” (Chudley & Greeno, 2006). There are numerous benefits to be had from using an eco-joist, the main benefit is that these joists are completely self-supporting which means that there is no need for any link ties to be used as with a standard wooden joist, this means that the construction costs are...
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