The construction of greenhouse walls is somewhat harder than it looks and the skill levels required will go up a notch. Building a wall perpendicular to the floor is not excessively difficult these days, particularly when laser levels are used.
However proper bracing necessitates a well thought out plan. You will require a design and materials that can support a roof and remain sturdy for several years.
One way to develop that plan is to either to purchase one from one of the many online websites that offer diy greenhouse construction designs, or study a house under construction since the same principles apply.
Either way you will require regular-spaced two by fours, usually sixteen inches apart, and/or a large number of L-braces, at least four inches per leg or longer.
Once you have the plans or after the actual greenhouse has been built, the fun part of the job begins for those who choose to exercise their woodworking skills on fixtures.
Any moderate-sized or bigger greenhouse will need one or more good table tops. Numerous types are available to buy, which is fine for those who prefer to go that route. However, most Do-it-yourself'ers will get pleasure from building their own.
Once again, it is good idea to draw out a suitable design before pulling out the hammer and nails or screws and screwdriver. Four by four, timbers make excellent sturdy legs. Make certain to buy or cut ones that have perfectly perpendicular ends to support the top.
One excellent and simple design involves laying a flat top, such as a series of one by twelve’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 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. Alternatively, 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 will need some simple shelving, but, for obvious reasons, if your walls are glass those shelves will need to be free standing. Sometimes, purchasing a couple of small, plastic sheds is preferable to building your own. After all, there is a limit to what even diy greenhouse construction enthusiasts want to make themselves.