How to build a whelping box for your English mastiff, or any other size dog for that matter.
You can determine what size whelping box you need, by making sure your dog had plenty of room to walk around the whelping box.
The purpose of the whelping box is to make sure that the mother does not get one of the puppies lodged between her and the box, and squeezes them to death.
English Mastiff's, or any other large size dog, can easily smoother there young, if they get laid on.
The way I made my whelping box for my English Mastiff, was I took a full sheet of 1/2 inch plywood, and cut it in half.
The floor was a 4 x 4 piece now, and I used 2 x 2 wood to make a frame on the inside and along the edges for a nice look.
I took 6 inch wide PVC piping you can bu from any hardware store, and I cut 6 inches pieces off of the PVC, and used them for the legs inside.
I used plastic PVC elbow joints to connect them together to a perfect 4 foot square that I could raise and lower pretty easy into the whelping box.
When you have the plastic PVC piping inside the box, it makes it harder for the mom to lay down against the sides of the box, when she is feeding her puppies, and if one gets stuck behind her when she moves around all the time, it gives the puppy that added air-vent below that keeps the moms weight off the puppy, and the puppy can survive.