I wanted to get my son a large chalkboard for his room because he likes to draw on a large scale. Unfortunately for him I'm horribly cheap and infinitely bored. Real, good quality chalkboards of any significant size are rather expensive so here is how i made a decent quality one for relatively cheap.
Step 1: Materials
There isn't much required.
48 x 48 piece of 5/8" plywood
48 x 48 sheet of 24 ga. sheet metal
Step 2: Plywood Base
I already had a 48 x 48 piece of plywood in my garage so that was the size i decided to make the board. Next, I picked up a piece of sheet metal from the local sheet metal union wear I work. You don't NEED to use sheetmetal for this project but it is necessary for another project I'm working on for later. I need the board to be able to hold strong magnets. I then trimmed the metal to 45 x 45 so that there would be a 1.5" border of exposed plywood around the edge. Lastly, I used liquid nails to secure the metal to the plywood.
Step 3: Poof! Chalkboard.
After the liquid nails set I painted the metal with some Glidden chalkboard paint from the hardware store. This paint is the most expensive part of the project. It is about $15.00 per pint. It is important that you follow the drying and curing instructions on the can. If you try to rush the paint it wont give you the nice smooth surface you need. Also, you should use a dense foam roller rather than a brush.
Luckily when I did this the humidity in my area was in the single digits and the temperature was low 90's. The paint dried and cured sufficiently within 2 days.
Once the paint was cured I dry fit some inexpensive wood base board for a nice frame.
Step 4: The Hangin'
The exposed plywood border was so that I could drive some 2" wood screws directly through to the studs. The whole thing is 15 to 20 pounds so I didn't want it to fall on my kids. Lastly, a few finishing nails and the base board made a nice finished frame.
The total cost for me was roughly $40.00.
Step 5: Update: Convert to a Dry Erase Board
After a while the chalk board got too darn messy, so we decided to convert it to a dry erase board. Total cost for the conversion was only $8.00!
First I scraped the chalk paint off. It came off really easily with a wide blade scraper. Next, I purchased melamine board from my local hardware store. Melamine is a type of board with a thin plastic coating and is usually used for making white cabinets. This melamine board was specifically for using as a dry erase board and is only 3/16" thick. It is available in 4' x 8' sheets but they were all out of that so I bought four 2' x 2' boards. A full sheet would look nicer because there wouldn't be any seams, but this works.
I put one full board on and then cut the other 3 to fit. If you score the plastic coated side a couple times the board just snaps apart. Being careful to keep the seams tight I used spray able locktite to adhere the boards to the metal. After the boards were all on I applied a coat of car wax to make sure any pores in the melamine were sealed. After you remove the excess wax you are good to go.