Concrete block garages are stronger and more durable than wood framed or steel garages. Because concrete block garages are thicker, they tend to be more soundproof. Concrete block garages are insect and rodent proof. They rarely fall down or leak in a storm. Constructing a block garage takes skill and know how, but don’t let that dissuade you. The building will require quite a bit of man power, and the costs are considerably more, but the pros far outweigh the cons.
Things You’ll Need
2-by-6 form boards
Double headed nails
6-mil Vapor barrier
2-by-8 pressure treated sill plate
Place stakes in the corners where your garage layout is. Dig out all the dirt 6 inches deep within the layout area. Set up 2-by-6 form boards around the garage perimeter.
Nail the boards together at the corners. Place support stakes behind the boards every 3 feet. Nail the stakes to the form boards with double headed nails so they are easily removed when you are finished.
Dig out your footings 1 foot wide by 18 inches deep around the perimeter. A footing is the structural part of the slab that bares the weight load of the structure above.
Place two 1/2 inch rebar horizontally all the way around the bottom of the footings, making sure the rebar is at least 3 inches away from the earth by placing a 3-inch by 3-inch dobey block every 3 feet underneath the rebar. Rebar is a structural steel rod manufactured to be placed in concrete to add strength. Rebar can be purchased at most hardware stores. Dobey blocks are small concrete blocks with tie wire bult into them to space rebar a given distance above the earth.
Place two 1/2 inch rebar rods also at the top of the footings. Keep the rebar 3 inches away from earth and air.
Attach 1/2 inch rebar rods vertically every 16 inches around the footings 4-inches in from the outside edge. These rods extend up. Concrete blocks are laid over the rods.
Tie the vertical rebar to the top and bottom horizontal rebar with tie wires. Tie wire is a spool of wire made to tie rebar together.
Pour 2 inches of sand into the garage slab area and a 6-mil vapor barrier between the sand. Although the vapor barrier isn’t mandatory, it is highly advisable. The vapor barrier is a plastic that keeps the concrete slab from sucking moisture out of the earth. Without a vapor barrier your slab can develop a white lime substance coming through and discoloring your slab.
Rake the sand flat and lightly moistion the sand to make it harder so it stays flat under pressure. When you place your concrete over the wet sand it doesn’t suck the moisture from the concrete, thus weakening the concrete.
Lay out your 1/2-inch rebar grid over the sand. A rebar grid is rebar that runs in two different directions adjacent to each other. Use your rebar tie wire and tie the two rebars together at all intersections.
Lay 2-inch dobey blocks under the grid where the rebar intersects. These blocks keep the rebar off of the ground preventing possible corrosion. Tie the rebar intersections with tie wire.
Fill the footings with concrete allowing it to flow over onto the slab foundation. It will be a monolithic pour, which means it’s a single pour; footings and slab done in one pour.
Transfer the measurements from the floor plan to the garage slab. Establish a chalk line from one corner to the other on all sides. The face of the blocks will be laid on this line.
Start at a corner and place a 1 inch thick glob of mortar with a trowel around the rebar rods, but not completely covering the full area underneath.
Press the 16 inch block in place firmly over the rod leaving a 3/8″ joint. Make sure the first layer of blocks is laid straight and level. Place all the corner blocks the same way.
Install the lead blocks, which are blocks extending out from the corner blocks, four blocks long.
Use a trowel and place a vertical bead of mortar on the side of the block already in place and set another block up against it. The mortar creates the joint between blocks. Do the same for all blocks going up.
Install the blocks on top of each other in a staggered position, not directly over each other. This creates a stronger wall.
Lay the blocks over the reinforcing rebar rods as you come to them. When the block gets too high and you run out of rod length, tie in new rebar rods to the existing rods with a 10 inch overlap, using heavy duty tie wire to connect them.
Using a concrete mixer, pump p-gravel concrete, also called grout, into the tops of all the blocks. You need to pump P-gravel into the block walls every four to six feet. This concrete will flow to the bottom and fill up all the blocks with concrete, giving your garage walls extra strength.
Step Twenty One
Place the 5/8 inch by 12 inch foundation bolts in the tops of your blocks before the concrete dries. The bolts are placed in the concrete so you can bolt down your first sill plate to the wall.