An office chair can be expensive to purchase new and often they are not comfortable enough to justify the expense. Luckily with a few dollars, some ingenuity and recycling, you can turn an old car seat into a comfortable office chair. You will need a few power tools and you will do some heavy lifting. Making an office chair comfortable and attractive will take about a day and it won't break the bank.
Find the right car seat for you. You should be able to pick up a car seat at your local junk yard. The seat will cost between £9 and £65. You may choose a seat that retains its power adjustments. (This will require more work when mounting the chair.) Or you may choose a seat solely for its comfort. Choose a seat you can imagine sitting comfortably in for hours at a time.
Bolt the chair to the plywood. Measure the base of the chair. Using a table saw, cut the plywood to the same size. (You can also get the plywood cut to the correct size at your local hardware store, usually for free.) Cover the plywood in upholstery fabric to match the chair. Finally, bolt the chair to the plywood piece, making it as secure as possible.
Mount the chair to the base. Take a base from an old office chair, and carefully place the car seat on it. It may take some adjustments to find the correct balance. Once the chair is placed properly, screw the chair in place. Now your office chair is ready to roll.
Make sure the chair base is strong enough to hold the car seat and your weight before placing the chair on it. Ask a friend or family member to help you with the heavy lifting. If you choose to keep the power adjustments, read Arrick Robotics' How-to guide for making the ultimate computer chair (see References). If your car seat is unattractive, you may choose to reupholster it before going on to step 2.