What is Brickwork Gauging?
When constructing any building using brickwork, the term Brickwork Gauge will become so very important. Most bricks today are manufactured to a standard size of 215 x 100mm x 65mm, 65mm being the depth. You should always have a bed joint of 10 mm, this will give us a combined brick and mortar depth of 75mm, from this should always think in multiples of 75 mm. You will spend many hours making sure your building is built to this gauge.
Most door and window frames today are built to a size that suits brickwork gauge and you must strive to build your brickwork corners to finish at the top of all openings to the millimetre, getting your gauge wrong will create not only structural problems, but will look terrible to the eye. The easiest way to make sure you get things right is to make yourself a Gauge Rod, you should make this out of a fairly small piece of timber, possibly from roofing batten and cut it to height of your finished wall and marked with multiples of 75mm. Use saw marks rather than pencils marks as it will make it a lot easier to see.
Gauging brickwork is a must have skill, you will never gain the skill of being able to guess by eye, the gauge of your brickwork, no matter how long you have been a bricklayer, having a gauge rod has many advantages over constantly using a tape measure once you have established a Datum Level. A Datum Level is normally set at your FFL (finished floor level) This would be the level at which your doors would be set, normally the head (top) of the door would be the head of your windows. On most projects these openings will all finished at the same level, hopefully you will understand the importance of getting all the openings at the exact same height, many problems will occur including:
• Having to increase the size of bed joints towards the top few courses
• Cut thin slices of brickwork to get to exact level of opening
• Being too high on one or more openings will make the Structural Lintel to high over some openings
• Course of brickwork over lintels will need cutting, which will look terrible and not structurally sound.
A Storey Rod differs slightly in that it is normally made to a length that is the height from FFL to the underside of the next floor, commonly the underside of ceiling joists. Then another is made that is cut to a length that is from first floor joist height to the underside of the roof (allowing for the wall plate). It is better to have a Story Rod for each floor to avoid confusion.
Commonly there would be a few basic items marked on the storey rod:
• Underside of window cill
• Head of windows
• Head of doors
• Service holes needed through wall
A Datum Point on a building would be an established point of reference often relating to the FFL (finished floor level). Your building foundations would be commonly built up to this point, which is established either from an existing building or through a Benchmark.
A Benchmark is a permanently affixed point that will establish a point above sea level, these marks are used by surveyors to map out the exact point above sea level in over a half million points in Britain, they can be found on buildings or stone pillars around the country. These points are more commonly used for new road projects or housing sites and form a network of reference points were we can establish a Datum for our building.
Once you have your foundations constructed and to the correct level, you will have a fixed point to place your Gauge Rod or Storey Rod. Once you have a few courses built, a nail would be placed in the joint at FFL at every corner, so that as the building progresses in height, you can always place your rod firmly on the nail to establish any heights you require.
For the experienced building professional this article will not be news, but if you are a novice then it is well worth reading and maybe investigating some of the points further, as always, if you are in doubt, contact your local building professional and he will be more than happy to help.
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