Square, or less commonly rectangular pillars tend to be built in areas, such as those of sandstone, where there are plenty of square stones, called quoins, for making the corners. Round pillars require lots of small stone, or stone which can be shaped easily. Even given good stone, both types require time and patience to build successfully in dry stone work, and frequently a mortared structure is built instead.
Pillars are used as an attractive way to end a wall, to frame a gateway or to hang a gate. Occasionally they are also seen free-standing, as memorials or cairns. Pillars used for gate-hanging are usually mortared, as the pillar has to take the weight of the gate, as well as providing a secure fixing for the hinge. See here for details of pillars and gate hanging.
Foundations
A pillar is one of the least stable forms of dry stone work, so it’s normally best to build on a concrete foundation, as any uneven settling may cause the pillar to topple. Use a mix of 6:1 aggregate:cement, tending to 4:1 for wetter conditions. The foundation should be about 6″ (150mm) thick, with the top finishing about 8″ (200mm) below ground level. Some wallers use the frame (see below) as formwork for the concrete, so the area is exactly the same as the pillar. Others maintain that the concrete base should be larger in area, to help spread the load, but this makes it less easy to secure the frame assembly. This is explained further below.
When building on bedrock, or in a remote location to which materials for concreting cannot easily be transported, make foundations as for a dry stone wall, using large, blocky stones. Make the foundation larger in area than the pillar, by perhaps 6″ (150mm) all round, with the exact dimensions dependent on the stone available.
Frames
Specialist frames can be used to construct pillars, although these are expensive to make for a single use only. Methods for constructing pillars without frames are outlined here.
Design
A simple frame for constructing square pillars can be made of 2 x 1″ (50 x 25mm) timber, joined with metal brackets. The frame is supported by four metal rods, about 1″ (25mm) diameter, slightly thicker than those used for line bars. The bars should 18-24″ (450-600mm) longer than the height of the pillar, and pointed at the base. The bars are secured to the frame with an adjustable clamp, as shown on the circular frame below. These clamps may need to be specially made by a local metalworker. An alternative is to have the frame itself made of 4-6mm x 50mm (2″) steel, welded at the corners rather than bent to shape, to give exact square corners. Any internal welds must be ground flat. A circular frame can be made similarly.
Installation
- Place the frame, without the bars, on the completed concrete or stone foundation. If the foundation is exactly the same area as the pillar, the bars can be driven down into the ground beside the foundation. If the foundation is bigger, you will need to first build one or two layers to bring the stonework up to ground level. Backfill around the stonework and tamp down well to give yourself a firm base to work from. The bars can then be knocked into the backfill to secure.
- Place each bar in position through a clamp, and drive at least 6″ (150mm) into the ground, until fairly stable.
- When all the bars are in position, raise the frame to near the top and check that all the bars are vertical, making minor adjustments as necessary.
- Lower the frame back down to the base, and if the bars are outside the foundation, drive them in another 6″ (150mm) or so, until fully secure.
- Raise the frame again for a final check.
Use
- Set the frame on the base to place the first layer of stone. Each stone should just brush the frame, without butting up tightly or the frame will be difficult to raise. If the stones do not brush the frame an accurate shape is difficult to achieve.
- Raise the frame for each subsequent layer, so that its base is level or just above the top of the previous layer. Experienced wallers may prefer to raise the frame in increments of 12-18″ (300-450mm), judging the layers between by eye or by using a spirit level. Check that the frame is level, using a spirit level, and ensure that the bolts just nip the bars to reduce the chances of distorting the frame.
- As the pillar gains height, check every 12″ (300mm) or so that the bars are still vertical.
Alternative methods
Where frames and bars are unavailable or inappropriate, alternative methods can be used to build an accurate pillar.
Square pillars
Some wallers use the frame without the bars, initially using the frame to mark a square in the mortar for the foundation, or as a template for setting the foundation stones. If not using a frame, some form of square is essential to accurately form the right angles. Check that the square is accurate by measuring both diagonals, which should be the same length.
Once the foundation stones are set correctly, you can follow these for subsequent layers, making frequent checks with a spirit level. You will need a long spirit level, preferably at least 3′ (900mm) long. Check the outside of both sides of each corner, and don’t be misled by just placing one stone up to the edge of the previous stone.
Once two adjacent quoins have been set, the stone or stones between them can be set in line by eye, and then checked with the spirit level.
Also check the width of the pillar as work progresses. Variations of up to 5mm on either side are acceptable, provided they are the exception rather than the norm, and that the pillar remains vertical. Use the frame every 12″ (300mm) or so to check that the pillar is square. Frequent checks on accuracy are essential when building pillars, as it is impossible to judge precisely by eye, because due to perspective, a pillar always looks wider at the top than the bottom.
An alternative method is to set four line bars at each corner. To ensure they remain vertical, use clamps to secure.
Round pillars
A fairly simple method of ensuring an accurate shape is to set a metal rod securely and vertically in the exact centre of the sub-base. Attach a string to a washer of only slightly larger diameter than the rod, and make a knot at the required radius. You can just tie a loop rather than using a washer, but this tends to be less accurate.
As you use the string to measure, make sure you are holding it level.
Problems
When you step back to check that no running joints are developing, look very carefully because the frame and bars tend to obscure the stonework and mistakes are easy to overlook.
Square pillars
Ideally, quoins should be flat with precise right-angled corners, but with uncut stone, this is not the case. There are various problems relating to quoins:
- The long axis of the quoin should be set level. If the stone is slightly tapering, set its base level, compensating for any slope when building the next layer. Severely tapering stones should only be used as quoins if there is another of complementary shape to sit on it. Use a wedge rather than place a sloping quoin, but avoid wedging if possible. Sloping quoins are not only structurally unsound, but will greatly mar the appearance of the pillar.
Avoid using wedges on the outside corner of the pillar, as the wedge is effectively the corner stone.
- Where the angle of the end of the quoin is not 90˚, and cannot be trimmed accurately, the longest axis should still be set in line as shown below. Set the stones, as 1 and 4, with the furthest point in line with the outer face of the pillar.
- However, if the angle is such that the stone above is largely unsupported at the corner of the pillar, you will need to trim the projecting point as shown.
End stones with a rounded profile can either be set back, or with the ‘nose’ protruding to make a feature. Setting the stone back makes it easier to keep building to the vertical. Protruding stones can look out of place unless they are a design feature, set at regular intervals, and they also make it more difficult to keep to the vertical.
The need to build four corners close together also causes problems. Ideally the quoins should alternate and tie each other in, but in practice they rarely fit this well. Normally you should place the quoins first, and then fit the stones between, which must be tight, but not enough to move the quoins. You need to leave gaps which can easily be filled. If a frame is not being used, you can work sequentially around the pillar, trimming the quoins to fit as necessary. A lot of forethought is required, and when mortaring, a ‘dry run’ may be needed for each layer in order to get it right.
You also need to think ahead in order to avoid running joints. The joints must be well bridged, and not just overlap by an inch or so.
Ideally, stones should be set in even courses, as a further problem occurs where the quoins are of differing height. As careful study of the diagram below will show, as you proceed from a level course upwards using quoins of differing height, at the height where the courses ‘catch up’, the quoins will be running in the same direction. In addition, you will have to use thin stones to even up the courses and a running joint is hard to avoid.
To solve this problem, level the pillar off at intervals and start again with alternating quoins. Some wallers level every two layers, others every 12″ (300mm) or so, but you are likely still to have a point where the quoins are not running correctly.
When levelling off, avoid using thick square quoins, as you will create poor overlaps as shown. A longer than normal quoin should be used instead. Alternatively, use wider and longer stones, even if they are thin, to level off. Plan ahead and save any suitable stones for this purpose.
Round pillars
Problems with round pillars are similar to those of curves. As the curve of a pillar is tight, small stones must normally be used. Larger stones need dressing to avoid the formation of large gaps, and mortaring is usually required.
Care must be taken to build accurately, with frequent dressing necessary, even for smaller stone. Instead of a frame, a template can be used, cut out of thin sheet metal or 6-8mm plywood. Some wallers make a template with a second sharper curve along one edge for use when constructing the inside of circular features such as wishing wells, which are effectively hollow pillars. Use the template to mark out the foundation, and then to check each quarter layer of stonework as you build.
For really accurate work, put the stone in position with the template over, and mark the stone with a nail or similar to give a line for trimming.
Most of the dressing of smaller stones will be of the inside edges, so they butt together well. Check frequently with a spirit level that the pillar is vertical, and also use the level to check that the layers are horizontal, or spiralling may develop.
Capping
There are various methods for capping pillars. Single slabs are the easiest, although for round, and most square pillars, slabs will have to be specially cut at the quarry. Smaller slabs will need weighting with a block, or with a series of slabs in diminishing sizes. Sometimes the initial slab is cut to project evenly all round, and an ornamental top is used to finish.
Vertical top stones are also used, although mortaring is usually needed to secure them. Square pillars need four square corner stones, and careful selection of other stones to fit in the centre. Round pillars require wedge-shaped top stones.
Because of the difficult of fitting vertical stones, square pillars frequently have two or four large and heavy stones for capping. These may be topped by another block, slab, or a series of slabs.
Tying pillars into walls
Square pillars tend to be built independently of walls, with the wall butted up to the pillar. This saves damage to the wall if the pillar moves, although tying the pillar into the wall can help stabilise it so movement is less likely. If the pillar is built on a concrete base then it is definitely better as an independent structure, as the settlement rates of the pillar and the wall will be different.
It’s also difficult to tie the stonework together unless the pillar is at least 12″ (300mm) wider than the wall at the base, or there isn’t sufficient space to fit the quoins. It becomes easier with height as the wall batters in, and the gap between the face of the wall and the corner of the pillar increases.
An unusual variation is to build a square pillar with sides battered to the same slope as the wall, which makes joining easier. In this example, on one side the pillar is simply an extension of the wall, and on the other side is about 12″ (300mm) wider than the wall, creating enough space to overlap the stones which form the join. As the pillar only has three corners, the number of quoins is reduced. In this case, the battered design was partly chosen as the pillars were subject to pressure from cattle, and it was felt these would be more stable than vertical-sided pillars.
Round pillars are much easier than square pillars to tie into walls, as there are no quoins to worry about. Don’t simply butt the pillar to the wall head, as an ugly gap will occur where the curving face of the pillar meets the flat face of the wall head. The technique for tying the two together is basically the same as used at wall corners.
Symmetry
In formal situations the symmetry of a pair of pillars can be quite important. If there are any notable stones, such as long quoins which act as ties running across the face of a pillar, try and place them to match on each pillar, to increase the appearance of symmetry.
Make sure the pillars match exactly for height by using a spirit level on a long piece of timber set on edge, spanning the gap. Alternatively, a special small level called a line level can be suspended from a taut line.
To fit a light on top, build the pillar up around standard 16mm copper piping with an elbow joint, through which the wire can later be threaded.
Gates
Pillars used for gate hanging need to be vertical, and a small amount of settling can create instability. They should be set on a concrete foundation.
Pillars which are used for gate hanging are normally mortared for strength. Use a 4 or 5:1 sand:cement mix, or a 7 or 8:1 aggregate:cement mix for the core of the pillar, in place of hearting. Use hooks or pins with long flanges, mortared in to secure. Alternatively, a metal post with long pins can be set into the pillar as it is built, as shown. This post will need to be specially made by a metalworker.
Dry stone pillars are usually only suitable for hanging small gates. Large stones should be built in at the appropriate heights to take the pins, which can be fixed into drilled holes using epoxy resin glue.
This pair of stone pillars on the Calf of Man have built-in recesses to take the gate, so leaving unspoilt the smooth curving faces of the pillars.
