Bricklaying: Use and care of line and pins
A line and pins are used to keep the bricks straight and level along each course of a wall. All brick walls over a metre long should be built with their aid. The line should be of good quality hemp and should not be too thick.
If the line breaks during use, it should not be tied together with a knot but the ends should be neatly spliced. The pins should be of good-quality steel and stoutly bladed, so as to prevent them from bending when in use.
Damage to the blade usually occurs when the pin has to be hammered into a hard mortar joint. This can be prevented by first driving a stout cut nail into the joint to a depth of about 20mm, and then withdrawing the nail, leaving a hole into which the blade of the pin is easily inserted.
When erecting a corner or stopped end of a wall, it is useful to leave ‘pin holes’ in the face of the brickwork, in preparation for the building of the wall using the line.
The pin holes are formed by inserting the point of the brick trowel into the one vertical cross joint of each course, before the mortar sets hard. The small slot formed by this takes the blade of the pin.
Before winding a new line on to the pins, suspend it over a hook and attach a weight to the end. This ensures that the line is well stretched and prevents it from becoming twisted during use.
A layer of insulation tape should be wound round the shanks of the pins before winding up to prevent the line from being affected by rust.
The ends of walls are always built up first and the builder’s line pins are tucked into mortar joints between each corner. The line is then ‘snagged’ over to the top edges of the quoin bricks and tightened by winding the slack on to the spade ends.
If you are building up to any height it is a good idea to make a gauge rod from straight timber marked with saw cuts at 75mm intervals. This is used to check that courses are going up evenly.
The spirit level is used to check that bricks are level, plumb and flush. Adjustments to the level of bricks is made by tapping these down lightly with the handle of the trowel then striking off with the trowel and returning to the spot board any excess mortar which is squeezed out.
Minor adjustments can be made by adjusting the thickness of mortar in vertical joints. If bricks have to be cut, it is best to use a club hammer and bolster, and steadily chop around the brick with even blows until it comes apart.
As walls are built, the joints must be pointed or finished while the mortar is still fairly soft. A flush joint is achieved by scraping horizontal joints with the edge of the bricklayer’s trowel and vertical joints with the ‘dotter’ trowel. Once the surface is dry, blemishes can be removed with a wire brush.
Tops of walls may be finished in a variety of ways. The most common is with capping or coping pieces. Coping, either half weathered (sloped one way) or weathered (sloped both ways), can be used on tops of walls. These are mortared in place, using ordinary bricklaying trowel techniques.
10. November 2011 by admin
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