Greenhouses What are they?.
Many people interested in having a greenhouse enjoy the prospect not only of using it, but of building it, too. Unless you purchase both the house and all its contents, you'll have to have some carpentry skills.
Many greenhouses have wooden floors. Relatively simple to construct, they can be made with 2 x 4's or 1 x 6's attached in a grid onto 4 x 4's that sit on the ground. Spaced a half-inch apart, that can allow drainage. Weeds that tend to grow between the slats can be kept under control with any commercial spray. Even the average do-it-yourself'er can easily make a good greenhouse floor in a day.
From that point, the skills level goes up a bit. Constructing greenhouse walls is a little tougher than it looks. Building a wall perpendicular to the floor isn't too difficult these days, especially using laser levels. But proper bracing requires a well thought out plan. You'll need a design and materials that can support a roof and stay sturdy for several years.
One way to develop that plan is either to buy one from any of the many sites online that offer greenhouse plans, or study a house under construction. The same principles apply. Either you'll need regular-spaced 2 x 4's (usually 16 inches apart) and/or a large number of L-braces (4 inches per leg or longer).
After you have the plans and/or the actual greenhouse built, the fun starts for those who prefer to exercise their carpentry skills on furniture.
Any moderate-sized or larger greenhouse will need one or more good tabletops. Many types are available for purchase, which is fine for those who want to go that route. Do-it-yourself'ers will enjoy making their own.
Here again you need to draw out what design you want before pulling out the hammer and nails or screws and drill-screwdriver. 4 x 4's make excellent sturdy legs. Be sure to buy or cut ones that have perfectly perpendicular ends to support the top.
One excellent and simple design involves laying a flat top (say a series of 1 x 12's with cross supports or a flat, sturdy piece of plywood) onto the legs. Nail or screw the top down onto the legs so you have something level and fairly sturdy. Then use some L-braces to increase the support in the horizontal direction.
Cap it by using plywood strips or 1 x 6's perpendicular to the top. Connect them to both the legs and the top with L-braces. Rock solid and attractive. Stain when complete to keep moisture from corroding the table.
You can use the same method to build benches for holding rows of plants or to sit on. Or you can use a trio of 2 x 4's attached to short 4 x 4's or crossed 2 x 4's, supported by a 1 x 10 running vertically down the middle and attached with L-braces.
You'll want some simple shelves, but if your walls are glass they'll need to be free standing. Sometimes, purchasing a couple of small, plastic sheds is preferable to building your own. After all, there's a limit to what even do-it-yourself'ers want to make.