Wall heads

The wall head is a specially constructed pillar which acts like a huge bookend to strengthen the wall faces and protect the centre, which would otherwise weather away and collapse. Heads should be built at the start and finish of every distinct section of wall, including:

1. Where gates and other openings are taken through the wall.
2. Where a new wall butts up against an existing one. While it is stronger to lock the two, this requires taking down a section of old wall, and so should only be done where the old wall is to be rebuilt anyway.
3. On steep slopes, to provide stability and limit the formation of gaps.
4. In certain cases, to indicate changes in ownership of different wall sections. The two heads are built against each other, and the coping is built across the seam to reduce its weakness.

Standard wall heads

The ends of a dry stone wall are the parts which are most exposed to damage, and the stones are only supported on two sides rather than three. For these reasons the heads should be built of the biggest, most regular stones available, which should be selected and put to one side during sorting. Stones may need to brought in if the local stone is inadequate. Large granite or sandstone blocks are best, preferably with smooth square faces on the two or three sides where they are exposed. Take care when handling heavy stones.

Procedure

When starting a new wall, build one head first. When you near the far end, build the other head and then complete the wall to close the gap.

When rebuilding heads it is best to dismantle the wall at least 6′ (2m) along from the head, placing the building stones to either side of the wall as normal. Leave plenty of space for working. Separate the ties, which are long stones that run across the wall, from the runners, which run along the wall. Pair the runners for height as you go, placing the largest on the ground nearest the wall. You may need to select suitable additional stones, such as throughs, from the rest of the dismantled wall to give you a better choice.

Having excavated the foundation, the procedure is as follows:

1. Set up the batter frame or line bars as described here. The frame can be set up immediately adjacent to the head where it will give the profile and the vertical line, but as it tends to get in the way when placing large stones many wallers prefer to set up the frame about 3′ (1m) beyond the end of the foundation.
2. Select a pair of even-height stones and set them with their long axis along the wall. Preferably choose a pair which will meet in the middle, but failing this select a stone of the same height to fit tightly in the gap between them.
   
   Don’t place foundation stones like a tie, with their long axis across the trench, as the lack of length along the wall means they are more likely to get undermined by erosion, particularly in gateways. Occasionally you may have a slab so large that it can run across the trench, whilst also having sufficient length along the wall.
   
3. Continue laying foundations away from the wall head for at least 10′ (3m).
4. Place a tie stone across the wall, taking care to choose one which is long enough to completely traverse the wall. If it is a little short you are likely to lose the correct batter or not be able to build on it satisfactorily. The correct place for this stone will be a little higher up the head.
   
   If you have a stone that is just too long use it now, as it will certainly be no use higher up. It’s generally not worth shortening a tie unless a trimmed finish is required, as it’s easy to take too much off. It’s best to place long ties so that they project equally on both sides of the wall, but local practice varies. Ties that protrude tend to get dislodged by cattle.
5. Build up a short section of wall to the height of the stones just placed, using ordinary face stones and fillings.
6. Continue to build up layers in this way, alternating ties and runners. Build up a short section of wall along from the head at the same time, leaving it well stepped for joining into later. Any gaps between runners should be tightly packed with smaller stones, and firmly gripped by the next tie.
   
7. As you build, keep checking with a spirit level or plumb bob that the head end is vertical. Some wallers set a single bar vertically in the ground against the head as a guide, after placing the first tie.
8. Try and arrange to finish the head with two runners rather than with a tie, as this gives the strongest bed for the topstone.
   
9. Finish the head with a large square topstone, as shown here. This must be heavy enough to resist the push of the rest of the coping against it, and should sit firmly without wedging. Too small a stone here and the coping will be insecure.

Further considerations

1. A common fault in heads is an absence of good runners, which results in running joints or insufficiently overlapped stones close to the head. As the head is vertical, it must be well bound into the wall to be stable.
   If necessary, use one or two throughs from the dismantled wall as runners. Heads are inherently unstable, and overall the wall will be stronger if it has a good head and one or two missing throughs. Ensure that all joints are well crossed, trying to achieve ‘half on one and one on half’. Don’t place wide ties on short runners.
   
2. It’s sometimes a good idea to try and use longer runners half way up and even higher, even if this means departing from grading and placing thicker stones on thinner ones. As it is the upper part of the head which is most likely to collapse during settlement, it makes sense to ensure it’s really well tied into the wall. The only limiting factor is that longer runners tend also to be wider, and may be too wide to place in pairs as the wall gets narrower.
3. Heads tend to be vertical because they often form the side of a gateway. Where this is not the case, the head can be built with a batter.
4. Heads should not be ‘pinned’; that is, they should not contain small thin stones, which can easily work loose during settlement. Where you have to make do with less regular stone, pinning may be unavoidable, in which case it should be carefully tapped into place to tighten the ties and runners after the head is built.

Mixed stone types

Generally wallers do not like to mix types of stone in a wall, as the different surface properties and shapes of different types of stone may not bind well together. However, the importance of using good runners and ties in a head may take precedence over using the same type of stone. In the fringes of limestone areas bordering on sandstone, heads of limestone walls often contain sandstone, which is better than most limestone for making heads, unless the limestone is level bedded. In the Lake District, slate is often mixed in with the more predominant stone type, as shown in this example from near Troutal in the Duddon Valley.

Many wallers in the slate areas of North Wales avoid using slate because they believe it fractures too easily, but there are plenty of examples in the Lakes which suggest otherwise.

This example at Mynydd Llandegai, North Wales, shows the successful use of thin stones and mixed stone types, with the head built out of reclaimed fencing slates about 5′ (1.5m) long, and the rest of the wall built of small, rounded field clearance stones, which are completely unsuitable for a head.

Non standard wall heads

Sometimes suitably long stone is not available, and other patterns of wall head emerge.

L shaped

This method, also known as ‘broken ties’, essentially follows the procedure described above. However, rather than alternating runners and ties, the head is built in a series of overlapping L shapes.

1. Place the ‘broken tie’ across the end first, ensuring there is enough space for a good runner.
2. Place the runner, ensuring a good fit. Try and combine the stones in such a way that the runners and ties always touch in the middle of the wall, avoiding the use of smaller building stones to fill any gaps.
3. Build up a short section of wall to the height of the stones just placed, using ordinary face stones and fillings.
4. Repeat these steps, placing the broken tie on top of the previous runner, ensuring there is a good overlap onto the previous broken tie.

Occasionally some of the stones used might make suitable ties higher in the wall. However it is usually easier to continue with the L shape, rather than to try to revert to the standard pattern or combine the two patterns. The problems encountered with the latter are detailed below.

Overlapping

This type of head is rarer than ‘L shaped’ heads, and normally only occurs in walls where there are a lot of large slabs of stone such as slate, mudstone or schist. A number of good examples can be found on the National Trust’s Ysbyty Ifan Estate in North Wales.

In effect these heads comprise almost entirely of tie stones. From the side the wall appears to have runners, but these completely straddle the wall and so also act as ties. Some pairs of runners are mixed in.

Grade the slabs with the largest at the bottom. The size difference in the slabs means it’s difficult to achieve smooth faces to the head, but as long as the overall ‘A’ shape is maintained the structure is sound, and a lot of movement would be required to displace any of the stones. A drawback is that the flatness of the slabs may require some pinning to prevent them rocking.

Combinations

With some walls it may be necessary to combine two, or even all three, of the previous methods. ‘Standard’ and ‘overlapping’ can be satisfactorily combined, but when mixing the ‘L shaped’ method with any other, care has to be taken to avoid running joints, or only slightly overlapping joints. Problems arise because you will either be placing a runner on top of another runner, or ‘broken tie’ on top of a tie, or vice versa.

Consequently it’s important to overlap the stones as much as possible. This necessarily involves having either much shorter or much longer runners, and wider tie stones as shown.

Single stones

Occasionally one comes across heads made of a single large stone or boulder, such as the milestone heads of Little Langdale in the Lake District.

The diagram shows head stones in a gateway at Mains of Murthly, Aberfeldy, Perthshire. Normally such stones are set in only about 4-6″ (100-150mm), although stones used to hang gates may be set in 2-3′ (600-900mm). The sheer weight and bulk of the stones keeps them in position. In this example the taller, thinner stone has been leant back into the wall, which compensates for its smaller base size.

Thinner slabs can also be used, and are surprisingly stable if set well into the ground.

With these types of single stone heads, care is still needed with the construction of the wall up to the boulder or slab, as a running joint is created. The end stones must have length into the wall, in effect building a rough head behind the single stone.

It is generally advised that a gate should be hung on a separate gate post, whether of stone or wood, set about 2″ (50mm) from the head of the wall. If the post gets knocked or moves with use, the wall is not affected. However, single stone heads do get used as gateposts, especially where there is a shortage of suitable ties and runners to build a separate head.