Ideally, your dog lives inside with the rest of the family. But in instances when he stays outside for extended periods, he needs a safe, comfortable place to shelter. Besides water and a source of protection from the elements, his kennel needs waterproof, overheating-resistant flooring to safeguard his feet.
Dirt and grass are great for running and playing on, but in the kennel they get muddy after rain and can quickly become unsanitary and harbor parasites, posing health concerns. Loose materials like wood chips and straw, which turn sodden and spongy when wet, are similarly less than ideal. Instead, use untreated wood decking over gravel or concrete for a softer platform with good drainage. Paint the wood with nontoxic outdoor paint for rot- and weather-resistance. Never use treated wood, which contains toxins that could harm your dog if he chews or lies on it.
Plastic flooring comes in quite a few forms – planks, solid sheets, insulated units, tiles and so forth -- and all forms offer some advantages over other materials. Plastic is lightweight, easy to arrange and inexpensive to ship. It is waterproof; it often incorporates sun-, mold-, mildew- and stain-resistant elements; it withstands weather extremes; and, when designed specifically for kennel flooring, it is usually guaranteed against chewing and scratching. In addition, it is a poor heat conductor so it maintains a reasonably comfortable temperature in hot or cold weather. It is also easy to clean.
Other Natural Surfaces
Natural rubber or bamboo mats are comfortable, safe options -- especially over hard surfaces like concrete -- and are removable for cleaning. You don't need expensive commercial products designed specifically for dogs. Shop for large rubber doormats or antifatigue mats like those used in workplaces, or check construction salvage stores for bamboo planking or tiles leftover from building projects. Ensure the materials are thick and substantial enough to withstand chewing; replace them when worn. Broken pieces may become choking hazards.
Gravel, Sand and Stone
Many dog owners use gravel or sand in kennels because it looks neat, drains well and is relatively inexpensive. Though those are definitely pluses, stone materials are not ideal kennel surfaces for several reasons. First, stone conducts heat rather efficiently. That makes it cold to lie upon in winter and hot in summer. Second, sharp particles of gravel and sand can stick to your dog's paws and cause cuts or bruises. Third, loose materials invite bored dogs to dig, so eventually dirt and weeds mix with the neat gravel floor and morph into the unkempt, dirt-floored kennel you were trying to avoid in the first place.
In many ways concrete is an ideal kennel floor surface -- for humans. It is durable, weatherproof, easy to clean and neat-looking. It's uncomfortable for your dog, though. Concrete, like stone, heats and cools with the weather, makes a hard bed to lie upon and can abrade soft foot pads. You can fix the problems and retain the benefits however, by pouring the concrete pad so that it slopes slightly, for good drainage, and by building at least one raised platform of wood or furnishing rubber or other padded surfaces for your dog's comfort. As an alternative to a solid slab, consider making a partial floor of concrete pavers planted between with a durable ground cover like elfin thyme or Irish moss to help mitigate temperature extremes and make a more comfortable surface.
Always check plant toxicity using lists provided by animal welfare groups like the American Society for the Prevention of Cruelty to Animals before planting in dog areas.
The Humane Society of the United States recommends never using wire grid as any part of the flooring in your dog's kennel. It is uncomfortable, unsafe and unsanitary, and can lead to a variety of physical and mental problems.