Building a Concrete Block Garage: Mistakes to Avoid

A wall made up of concrete blocks.

When considering the construction of a new garage, you should definitely consider the advantages of using concrete blocks. Not only are they stronger than garages built from framing or metal materials, but they are generally more leakproof, soundproof, and resistant to fire. Although this material is generally more expensive than other types and its construction takes more installation time, owners who have built both the concrete block garage and the framed garage will typically say its advantages far outweigh the additional time and cost. If you're considering the construction of your first concrete block garage, You'll be wise to avoid some of the typical mistakes made by first-timers.

Removing Too Much Topsoil

You’ll need to remove some of the dirt so that your concrete floor, when poured, will be level with surrounding land levels. However, you should avoid removing more than six inches of soil. Taking out more than this will result in your garage floor sitting below ground level and vulnerable to water that can seep in.

Placing Rebar on the Ground Surface

When your footings are in place and you begin installing your rebar, be sure it is laid horizontally and vertically along the bottom of your footings, approximately three inches above the ground level. You can ensure the proper height of these rebars if you first install a layer of three-inch adobe blocks three feet apart on the ground. Or, you can purchase risers made especially for that purpose. The advantage of using the more expensive adobe blocks is that there is no metal penetrating the slab below ground level.

Lay your rebar on top of these blocks, or risers. Without this spacing above the ground surface, you cannot be sure the rebar will be embedded within the concrete and it will not offer the same strength to the concrete as it would if it was properly set.

Failure to Moisten Your Sand Layer

The sand layer that supports the heavy concrete poured on top of it will need to be as hard as possible if it is to provide even support. To harden the sand, you will need to be sure the layer is raked even, moistened with water, and tamped down thoroughly. This moistening will also reduce the likelihood of your concrete weakening.

Failure to Use a Vapor Barrier

After pouring and leveling two inches of sand on the ground where you've removed the six inches of topsoil, you'll be pouring four inches of concrete. This concrete, unless a vapor barrier is then placed on top of the sand, will typically draw moisture from the sand on which it is resting. The result will be not only a white substance that penetrates and discolors your slab, and you will have a weaker floor also.

Pump Pea Gravel into Your Blocks

As you lay concrete block walls, pause installation at four to six feet levels and pour pea gravel concrete into the blocks. This concrete will flow down through the spaces in the blocks, filling them and making the wall much stronger. Failure to add this concrete will leave your walls without the added strength and support, which could lead to preventable wear or damage.

Concrete Block Garage Mistakes FAQ

What is the disadvantage of building blocks?

Concrete is a sturdy building material, but not necessarily perfect. There are some problems associated with concrete block buildings, not the least of which is water that seeps in around the blocks.

Concrete block buildings are also not very attractive and don't particularly have a lot of curb appeal. It is also rather expensive to build with concrete blocks, particularly if you're building a structure in a large size.

What is the lifespan of a concrete block building?

Buildings made with concrete blocks are incredibly durable and highly resistant to many problems that affect buildings made with other materials. Expect your concrete block building to last up to 100 years.

What is the difference between a cinder block and a concrete block?

Cinder blocks and concrete blocks look very similar but they are actually made from different materials. Cinder blocks are made from coal cinders and concrete, while concrete blocks are made of cement, steel, and wood.

Concrete blocks are heavier than cinder blocks.

Do concrete blocks need a footing?

All block walls need to be supported by a secure, stable footing. Otherwise, the walls could shift and sink over time and create severe structural damage to the overall building.

Do concrete block walls need insulation?

Without insulation, block buildings will be subject to cold and hot weather conditions. If the building's temperature is regulated with an HVAC system, space heater, or fan of any kind, energy bills will be very high.

Insulation can provide a lot of comfort and save a lot of money in the end, so it's well worth the investment.