Cat furniture is a commodity that is known by many names.  The most  common include Cat Trees, Cat Condos, Kitty Condos, Cat Towers, Cat  Climbers, Cat Scratchers and Cat Gyms.  There are dozens more, but  whatever term you use to describe cat furniture, the purpose is the same  - to enable your cats to follow their instinctual desire to scratch  without damaging your furniture, carpet, or other belongings, and  also  to give them a place of their own where they can exercise, play, and  lounge.
There are many different types of cat furniture, made from  such a variety of materials, that shopping for cat furniture can be  confusing.   Which materials are better?  What design is the most  stable?  What size should I buy? Which style would my cat like?  In this  article, I'll try to help you answer these questions so you can make a  more informed buying decision.
Why Do Cats Scratch?
In order  to be completely informed when buying cat furniture, it's helpful to  understand why it is that cats scratch in the first place.  The primary  reason for cats scratching furniture, carpets, woodwork, or other  objects is to mark their territory for other cats (this is instinctual,  so they will do this even if they are the only cat in the house).  Additionally, the scratching helps remove the dead cells from the claw  sheaths, and stretches their muscles and ligaments.
Feline  behavior is consistent, whether it's a tiger in the wild, or a Maine  Coon in a condominium.  Scratching is the way they say to other felines  in the area "Hey, I'm here, and this is my place".  Scratching  communicates this in two ways. The first is obvious - the scratches  provide a very visual cue to other cats.  Additionally, cats have scent  glands in their paws, which leave pheromones that other cats can smell.   For those of you that have experience with declawed cats (PLEASE don't  declaw your cats!), that's the reason that they continue to scratch even  after the claws have been removed.
Cat Furniture Coverings
In  the past, most cat furniture was covered with carpet.  This was a good  choice, because it looks good, and it offers a material that cats  obviously like to scratch.  Some of the cat furniture manufactured  today, especially hand-made models, still use carpet.
Most  carpeting today contains fabric loops. Unfortunately, after thousands of  scratches, cat claws can cut through these loops, resulting in  unsightly and messy shredding. You've probably seen this yourself.
However,  with today's technology, engineers have developed an acrylic material  specifically for use in the cat furniture industry.  This material,  commonly referred to as fake or faux fur, has become increasingly  popular.  The main reason for this popularity is the fact that it does  not contain loops, so it doesn't shred like carpet does, and therefore  tends to last longer than carpet.  The drawback is that since it doesn't  offer the resistance that carpet does when they scratch it, cats don't  like it for scratching as much as they like carpeting.
As a  result, most cat furniture that offers faux fur also utilizes sisal rope  as a covering. Generally, the vertical posts are wrapped with sisal  rope, and the platforms and enclosures are covered with the acrylic fur.
Sisal  rope is made from the Agave Sisalana plant, which is native to the  Yucatan area of Mexico. Cats seem naturally drawn to this material, and  unlike the acrylic fur, sisal rope offers the resistance that cats need  to tune their claws and stretch their muscles.
Some cat furniture  manufacturers that use carpet as a covering also offer sisal-wrapped  posts, and in most (but not all) cases cats will scratch on the sisal  instead of the carpet.
Structural Materials
Obviously the  strength of the cat furniture is provided by the underlying structural  materials. Vertical posts are usually wood 2 x 4's or heavy cardboard  tubes, while horizontal surfaces are either plywood or pressboard.   Manufacturers sometimes use cardboard for enclosure walls that do not  bear any weight load.
It is a common misconception that wooden  posts offer more structural integrity than cardboard tubes. In  actuality, this is not necessarily true. Of course everybody knows that  wood is stronger than cardboard when flat. However, when thick (at least  1/4") cardboard is made into a tube, and stood up vertically, it can  hold an incredible amount of weight. The addition of a layer of sisal  rope wrapped around it adds even more strength. One big advantage of  cardboard posts over wooden ones is the weight.  Shipping rates are  based on weight, and shipping costs for a piece of cat furniture made  with cardboard posts will be considerably less than a comparable model  with wooden posts.
For platforms and weight-bearing walls in  enclosures, manufacturers generally utilize either plywood or pressboard  (also known as particle board).  Pressboard is fiber pulp that is mixed  with a chemical adhesive to create a smooth, uniform board. Plywood is  manufactured by gluing thin layers of wood together, resulting in a  board that is actually stronger than solid wood of the same thickness.
Generally,  plywood is preferred to pressboard for cat furniture platforms for a  number of reasons.  During shipping, pressboard is much more likely to  be damaged than plywood, especially if the carton is dropped on it's  corner.  Additionally, pressboard tends to crumble around the edges of  screw or bolt holes if the hardware is tightened too much. Pressboard  platforms are also more likely to break if enough weight or vertical  force is put on it, as happens if a child sits on it.
Floor-to-Ceiling or Freestanding?
Cat  furniture models will be either freestanding or floor-to-ceiling  (commonly referred to as cat trees).  Freestanding cat furniture is  usually wide and bottom-heavy, to prevent it from tipping over when cats  are at the top, or are very active.  Floor-to-ceiling models use  tension against the ceiling to provide their stability, and so do not  require as wide a footprint as freestanding models. A properly assembled  and installed floor-to-ceiling model cannot tip over. Usually, the  tension against the ceiling is accomplished either through use of a  spring-tension rod or a screw-based mechanism.  This doesn't mean that  the cat tree is screwed into the ceiling. Rather, the topmost post has a  threaded bolt, usually topped with a soft protective cap that screws up  against the ceiling. Generally, the screw-type cat trees are more  stable, especially if you have active cats, and are also less likely to  damage the ceiling surface.
So What Should You Buy?
The decision as to what type of furniture to buy for Tabby and Fritz should be determined by a combination of factors:
-  Do you want a freestanding or floor-to-ceiling model?  This is really  more of a personal choice issue than anything else.  If you have very  active or very large cats, a floor to ceiling model will probably offer  more stability.  If you have a multi-cat household, special attention  should be paid to the weight rating of the furniture.  It's also usually  possible to secure a free-standing model to a wall with common brackets  and hardware available at any home center, in cases where rambunctious  kitties cause it to rock or tip.
- Which covering?  Carpet offers  the advantage of more color choices, and if you're very particular about  your cat condo fitting in with your décor, this might be your best  choice. Faux fur models are generally made in neutral colors like beige  or taupe, although there are some exceptions.  In either case, having a  sisal scratching surface should be a goal if at all possible.
-  Structural materials. If you have a choice, choose plywood over  pressboard.  As for the posts, both cardboard and wood offer good  stability. As stated earlier, models with wooden posts are heavier and  may cost more to ship.
I hope that this article has been helpful  in explaining the different types of cat furniture available, and the  strengths and weaknesses of each type.  In the end, don't forget that  the safety and happiness of the feline members of your family should be  the most important factors in choosing cat furniture for them.