Why is my wall falling down?

Many walls are old and the actions of the weather ,environment and animals all play their part in eroding the stability of a well built wall.

However, there are common faults that will certainly weaken the structure of a dry stone wall.

Running joints:
A really common mistake that those of you who ever built with lego will recognise! Basically a running joint should be avoided as it will always be a point of weakness where a bulge or hollow will form when the wall is under any sort of force and movement.

 Spot the running joints and stone stacking almost from the top to the base of the wall

'Hearting' or Filler:
Often the things you can't see on a wall are the most important. A hollow wall, or a wall where the filler has just been thrown in will be weaker. The small stones that fill the gap between the two sides, give strength and flexibility to a wall. Where there is none, the wall will easily fall down, especially if any pressure is applied! Hearting is carefully placed....not just thrown in!

Poor packing thrown in
Compare to the picture below...stone is almost back to back and packing is tight and level...a much stronger structure

This walls below in Ambergate has no packing in the upper half...nothing to hold it together!

Most people imagine that cement will strengthen a wall and in some circumstances it will. However, where the land around is liable to move, a well built dry stone wall will adapt, flex and settle to any movement. When a wall is cemented, it cannot do this, so it cracks and splits as the land settles.

Do not plant trees near a wall....they don't get on, as tree roots grow the wall has no option but to move. If rebuilding around a wall I will leave breathing and moving space for the tree. In winds it'll move and therefore a gap will stop it nudging the wall. It will always be a compromise.

 A holly tree planted about 6" from wall. It will always impact upon the wall.
Here, I built a bridge over large tree roots to allow for growth

Many animals, horses, sheep and cattle enjoy a good scratch on a wall and where there is a protruding sharp stone this will serve it's purpose well...until the wall falls down!

Poorly built...
Yes, it does happen, unfortunately there are a number of poorly built walls which as you recognise what faults to look for you will start to see more and more!
Walls can be too narrow for their height, full of running joints, loose stones, soldiers (stones turned on their sides) large stones at the top rather than base of a wall, bulges, no or irregular batter (the angle of the sides) poor internal packing which is a major component of the wall's internal strength.
Below are some examples of poor walls, see which faults you can spot!