How to build a whelping box with rails

Updated November 22, 2016

Just like dogs, whelping boxes come in all sizes, from simple cardboard to fancy vinyl-coated wood. A whelping box provides a safe, secure place for a dog to have her puppies, but it is vital that you take your dog’s needs into consideration as you prepare her sanctuary. To prevent accidental squashing and suffocation of puppies, provide any large-breed dog with rails around the inside of her whelping box, creating a safe zone for the pups around the box’s sides.

Measure your dog’s body when she is lying on her side, stretched out. Determine the whelping box’s length by measuring from the top of the dog’s head to the base of her tail and adding 12 inches. Determine the width by measuring from the bottom of her front foot to top of her withers and adding 12 inches. Use these measurements to determine the size of the floor of the whelping box. Cut the single sheet of 5/8-inch plywood to this size.

Cut two of the 16-inch-high sides to the same length as the two longer sides of the base. Cut the third 16-inch-high side to the length of the shorter side of the base. Cut the 12-inch-high side to the length of the shorter side of the base.

Cut two pieces of 2-by-4 the same length as the longer sides, and two pieces of 2-by-4 the same length as the shorter sides of the base.

Attach one 2-by-4 to each plywood side, using three evenly-spaced angle brackets and short wood screws along the longer sides of the box, and two evenly-spaced angle brackets and short wood screws on each shorter side. Place the 2-by-4 boards 3 to 4 inches up from the base. The height is determined by your dog’s size. She should not be able to fit her back under the 2-by-4 rails when the box is assembled. Attach the shorter railings just high enough so that they will fit on top of the longer side railings when the box is assembled.

Attach the sides to the base, using the longer wood screws. Screw the sides together at each corner. Make sure you have a snug fit along the base and at all corners. Any gaps must be eliminated to protect the puppies.


Cover the base and sides with vinyl flooring or with plastic-coated shelf paper, if you want to make it easier to keep clean. If you do this, also use non-toxic silicone sealant to fill in all the cracks where the sides and base come together. Also cover and seal the safety rails, to make them easier to keep clean. It is easiest to do this step before final assembly.


Side rails provide an extra measure of security and safety for young puppies, but pups can be injured or killed despite these rails. Watch them closely at all times, especially during their first two or three weeks when they are not able to move out of their mother’s way quickly enough to avoid injury. In larger whelping boxes, pups may become separated from each other and scattered along the sides of the box. The rails can help to keep them from being squashed, but they still may die of exposure if not kept warm enough. Keep them together as much as possible. A waterproof heating pad can greatly assist in keeping the puppies safe and warm, but get one intended for use with dogs.

Things You'll Need

  • Sheet of ¾-inch plywood
  • 3 pieces ½-inch plywood cut 16 inches wide
  • Piece of ½-inch plywood cut 12 inches wide
  • 4 sections of 2-by-4
  • 10 angle brackets, 90-degree bend in each
  • ½-inch wood screws
  • 1 ½-inch wood screws
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