Information: How to fox-proof your chicken run.

There are various ways to fox-proof your chicken run. The one you choose in the end depends on how much space you have, if your run is already built, and your budget. Here are a few I know of, explaining how to stop foxes digging under. However, they can also climb so either covering your run with wire, a solid roof or fruit netting is a good option, and will also protect from hawks. Otherwise you could run a bit of electric fencing along the top of the fence. This will not protect from hawks though.

1. Basically just use small chicken wire, tacked to the bottom of the run (what I did for my bantam run) to basically make a wire floor. This doesn't really work if you plan on having a tractor (movable run) because they can't scratch or dust bath, but it is good for small, stationary runs because you can put woodchips/shavings/etc. over the top so that they can scratch. It must be one of the safest options. but can only be used for small runs, before it becomes very expensive.

Using a fox-proof "skirt" around the chicken coop and run.
Credit:  Moosicorn Permission:  CC BY-NC-ND 2.

2. I use this for the large fowl run. Attach wire to the side of the run near the floor. Then bend it so that it sticks out at the side for a little over a foot (not on inside of the run). If the wire isn't stiff you'll need to put  some soil over it and hold it down with a few bricks/stones or tent pegs. Obviously the run has to then be stationary, but you can also move it around if you use tent pegs to hold the wire down. This creates a kind of "skirt" around the base of the run, and is a good option for large, stationary runs.

3. Paving: this is another option. You could lay slabs down or concrete and place the run on top. There will then be no way for the fox to dig underneath. Then lay something down on top for scratching in. If you do want to move the run around then you could do so, and just put it on the slabs if you go away so your "chicken-sitters" don't need to worry about foxes!

4. This is similar to no.2, but instead of pegging the "skirt" down, you dig the mesh vertically into the ground, before filling it in. I've never tried it, but it is a very safe option.

5. You could try electric fencing, or an electric wire running along the bottom of the fence and again another one at the top, but it wont be as safe as the others.

Secure chicken run on slabs.
Credit: David Clegg Permission: CC BY NC-SA 2.0

The only time you really need to worry about fox-proofing is when you are away or if you don't want to lock them in and let them out of the coop twice a day. However, foxes do come out in the day, particularly if you live in an urban area where they won't be as shy. If you can, you might as well make sure your birds are safe from foxes and other predators also!