Question
I want to install a brick patio.  The specs are as follows:
size:  12' x 30'
level ground
2-sided border in concrete with motar.  Remainder in sand.
Questions:

Most important:  How many brinks to I need?  I am looking at red brick 4" x 8".  How important is it to put gravel?  Can I use just sand?  I am located in California.

Thanks you.

Answer
First, Brick is not really 4"x8". That is the "nominal size". It is usually slightly less to account for mortar joints. Also not all bricks the same. There are lots of non-standard sizes, specially for ground rated paver applications. Also some people mistakenly call concrete pavers, "bricks". I believe that the strict definition of brick requires that the material be made of fired clay. Thus concrete pavers should be called "concrete pavers". Pavers come in all sorts of sizes and shapes many much larger than 4x8. Clay brick also come in lots of sizes and shapes. So to be certain, once you find the exact brick paver or concrete paver you want you should measure it to be sure.

However, for a generic equation use this: 1 std brick = roughly 4" x 8" or 4x8 = 32"  32" divided by the number of inches in a sq ft (144" for 12"x12") gives you the number of sf per brick or 0.22sf. Your patio is 12x30 or 360sf so 360 divided by 0.22 = 1636 bricks. To be safe you should always order 5-10% extra as some will break.

Depending on your sub-base and the propensity for freezing in your area you may or may not need a crushed gravel sub-base. If you have a good sandy soil and it doesn't freeze then you probably can get away without any sub-base. However, if you have loose organic soil or it freezes then you need 4 inches or more of crushed granite to be compacted in place before adding a sand leveling bed.

Best of Luck

Sean J Murphy
www.seengineering.com
www.amenityarchitects.com