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There are many opinions on cages, in terms of construction and size. A young chameleon (approx up to six months) will be find in a relatively small cage (1'x1'x2') but an adult will need at least 2'wx1.5'dx4'heigh. Bigger IS generally better. what your cage is best constructed of may depend on where you live. Lots of folks in warm states use screen cages. I use a primarily wooden cage. The enclosure must be a large enough space so the animal may conduct all of its natural behaviors including, basking, hunting, nesting (females), drinking and feeding. IMHO I would suggest 2x2x4 or larger for an adult. But the key is to keep the environmental conditions inside the cage right.
to that end, your chameleon enclosure ought to accomplish the following objectives:
Space. Although chameleons are often slow-moving animals, they require a lot of space for their physical and emotional comfort, security and thermal regulation. Like I said, I think an adult should have a cage no smaller than 2 wide, 2 deep, and 4 high.
Height. In the wild, chameleons are arboreal, dwelling in the foliage of small trees. They naturally prefer to be above predators, (which includes you). The cage should allow the chameleon to perch above your eye level. Chameleons are arboreal creatures in nature and some species normally perch at heights of six feet or more. This gives chameleons a sense of security that should be factored into their captive environment. Cages that are less than six feet high should be placed on stands.
Ventilation. It should provide good ventilation on all sides and top of the enclosure, because Poor ventilation, such as in a glass aquarium or other solid-walled enclosure, traps stagnant air which can lead to illness. Large bird cages with coated wire are a good option, if you can find them both big enough in size but with bars close enough together to keep your chameleon enclosed. Mesh cages are a good option, but be careful to ensure your chameleons toes will never get caught in the mesh. Be cautious of using uncoated hardware cloth (chicken wire) as it can cut feet. I use a combination of wood peg board, screen and acrylic.
Predator-proof. Chameleons must be (and feel) safe from attacks by birds, cats, dogs, rats, snakes, racoons, curious children, etc.
Safely supports a lighting system, including at least one incandescent basking lamp for heat and one fluorescent lamp that emits UV-B, or a mercury vapour lamp that emits UVB, UVA and infrared heat, all in such a way that thermal burns are avoided.
Water. Facilitates easy removal of excess drinking water on a daily basis. Cages with screened floors work best for this purpose, or a sloped waterproof floor (plastic tray for example) that leads water to a drainage hole and collection bucket. As a volume of rapidly dripping water and misted water passes through the chameleons cage, the chameleon will lap water from the plants and branches, but the excess (which far exceeds the amount consumed) should drain into a catch basin (preferably under the cage). Enclosures with solid floors require an extra expenditure of effort to remove the excess water that accumulates on a daily basis.
Egg laying box. Has sufficient space to include a 2 x 2 x 2 nesting box for females, unless you plan to move her when she is ready to lay eggs.
Bonus: Allows exposure to direct sunlight. Whenever the temperatures outdoors are within the preferred range of your species, the enclosure should be transferred outside or you should have a separate outdoors cage so your chameleon can bask in the sun, which is the best source of UVB irradiation. However, you have to balance the benefits of natural sunlight with the stress of being moved and you need to ensure there is sufficient cool shade as well.
