Pyrs love to dig. They dig craters in your yard to keep cool in the summer and as snug beds for winter guarding duties. It’s no surprise that many take their skills to the fence line and manage to compress their impressive bulk into a slithering white rug that fits through that tunnel.
For those determined diggers, sinking rebar (steel reinforcing bar) posts a foot or two deep into concrete or Quikrete®, spaced several inches apart, can help prevent that. It may not be cost-effective if you have a large area to cover, but can be a solution for problem areas or when fencing runs over water (such as a creek)
One option is to lay a cement footer around the base of the fence—even embedding the bottom of the fence into it before it dries.
Alternately, you can dig down a foot or two and fill it with cement, building a solid trench that should stop the dog.
Another option is putting in “L-footers” or “dig wire.”
L-Footer: An L-footer is wire fencing laid down against the base of your fence and bent perpendicular (90 degree angle) to it: just like an “L.” You can bury this fencing underground, but it doesn’t have to be buried to work. Some people just lay it on top of the grass and maybe add some rocks to hold it down, but with a determined Pyr, you may need to bury it. You should have it extend 2-3 feet into the yard, and then bury it underground or tack it down and cover it with rocks, mulch, etc. Leftover cattle or goat panels, cut into three-sided pieces with a bolt cutter and pounded into the ground, make great fence staples.
This site explains it well (and has tons of other great tips).
Most diggers will be kept in by regular “2 x 4” weld-wire fencing, though some may require heavier gauges, chain link, or strips of cattle/goat panel.
In the case of weld wire, the edge of the ground fence is bent 90 degrees up, then attached (with pig rings or wire) to the vertical fence. You can make this more economical by cutting 5′ weld wire fence lengthwise, alternating your cut to either side of the split, then using the alternating uncut wires to attach the 2 1/2 foot skirting to the fence. Cattle panel and chain link lay flat, and just need to be attached securely to the fence with hog rings or heavy wire.
There is now a manufacturered alternative to weld wire called “Dig Defence“. The XL size would be suitable for most Pyrs. This page shows how it is installed. To watch a Youtube video, please click here.