A garage is a valuable addition to your home. Not only for your cars, but a garage is also a strategic storeroom for your tools and equipment. The longevity of a garage is significantly determined by how solid its foundation is. A garage with a weak foundation will crumble in no time.
Yes, a garage needs a foundation to support the outbuilding and sustain its structural integrity in the long term. This ensures the garage structure is strong and stable enough to carry the load and even survive unfavorable weather conditions. Concrete and metal are some of the best materials for building a garage foundation.
Garage foundations require a lot of technique and diligence. You need the right choice of materials as befitting for the soil structure you are building on. You also need expert engineered drawings of the building plans. A tiny critical error and your garage will collapse too soon.
What Is the Best Material for a Foundation?
The materials used in building your garage foundation depends on the region and subsoil. But these are the best materials required to lay a quality foundation:
Concrete is the most reliable material that can be used for building garage foundations. The advantage of concrete is its ability to mix exceptionally well. When you pour the concrete properly, it makes the work of building your garage easier. Before working with concrete, you must construct a wooden frame where the concrete is poured. This allows it to set, and the frame will be taken off before the foundation can stand on its own.
Metal provides more solidity and strength. The metal is inserted inside the concrete before it sets and is one of the most reliable materials used in building garage foundations.
Also called breeze blocks, they are much larger than standard bricks and are lighter than regular blocks. It is advisable to use frost-resistant blocks, which ensures water cannot get into it and destroy the integrity of the foundation.
Garage foundations mostly remind people of concrete. But do you know wood is one of the right ways to give your garage a solid base? Use woods that are chemically treated to prevent rot or pests.
Damage from the elements is something to be wary of. Make sure you buy weather-proofing materials to give your garage a longer life span.
How Deep Should Foundations for a Garage?
The depth of a garage foundation is crucial to its longevity. This determines how strong the garage will be in the long run. You have to consider the building conditions when digging your garage foundation. Basically, you have to dig footing of 2 feet (minimum) in width. This should be as deep as the frost line. In some cases, you can dig as wide as 6 feet when additional width is needed.
If you are building a one-story garage, a depth of 8 inches is suitable for the garage so long it has a corresponding width of 8 inches. A two-story garage will need more depth in its foundation. Hence you can go with a 10 inches deep foundation, which is also 10 inches wide. The depth of your foundation must correlate with the local building codes.
How Do You Notice Good Soil to Build?
Once you dig to a decent depth, you will see a difference in the bottom layer of the topsoil. The depth at which you notice the difference depends on the area. It could be from 10″ to 18″ depending on location. It also depends on how much the first developers have altered the site. Because it is hard to say, you will generally notice the subsoil at the bottom feels different from the topsoil before the dig.
Furthermore, it is possible to hit another different layer of subsoil. This is usually the most ideal for building on. But if you dig into clay, be prepared to dig a further meter before building. Most of the time, the local councilman can prescribe a suitable depth for your area. But if this is not the case, then your aim to reach for firm subsoil before building your garage foundation.
Another thing is to ensure the trenches are not left exposed for long periods. This could make them vulnerable to bad weather, which could flood or dry out the trenches. Make sure you pour the concrete as soon as they are dug.
What Are the Three Types of Foundations
There are three types of foundations commonly used.
Slab-on-grade foundations are more suitable for buildings in rocky areas. Examples of such regions include Texas and Oklahoma. This type of garage foundation is ideal for those in areas where frost-depth is not a big problem.
Slab-on-grade foundations are constructed from a horizontal-shaped concrete slab set into mold. This is done such that the mold is taken off your concrete sets. The garage measurements must correlate with the dimensions of the preset slab. In some cases, slab-on-grade foundations would need steel reinforcing. This is executed with a 10 gauge wire mesh.
Hybrid stem wall garage foundation
The hybrid stem wall garage foundation is more suitable if you are building your foundation on an area with poor soil drainage. This is common in areas with significant soil expansibility. This is peculiar to regions with problematic frost heave.
In these soil regions where the bearing capacity is not too impressive, hybrid stem wall garage foundations are your best bet when building garages with more than one story. This foundation design will allow for improved distribution of the load.
Stem wall garage foundation
This type of foundation is suitable when you are building garages with more than one story. When you have a dwelling above the first story of your garage, then you will need to spread the load appropriately, so the structural integrity of the foundation is maintained.
This is where the stem wall garage foundation becomes vital. The stem wall garage foundation has a concrete stem wall sitting it on it. Agreed, this foundation works best with a base of reinforced concrete spread footing.
When constructing this type of foundation, you need to separate the garage foundation walls from the floor slab. This is achieved via an expansion joint wherever the floor meets the wall surface. Note that the floor slab is poured independently.
You will have to consult local authorities to ascertain how deep your spread footing should be. In most cases, such local authorities will factor in the annual frost depth and determine the befitting spread footing depth for your stem wall garage foundation.
Can I Build a Garage on a Concrete Slab?
You can build a garage on a concrete slab. There are, nonetheless, some critical considerations to take note of. This cuts across how you intend to use the floor, weight, thickness, and of course, your budget. To get the best value, your concrete garage floor should have a depth of six inches enhanced with good control joints.
This will give it the tolerance to withstand heavy and standard usage. This brings us to how you intend to use the concrete slab.
The purpose of your concrete slab will determine the thickness clearly.
A garage accommodating trucks will understandably have thicker flooring than one just housing cars. If you are going to park light cars on your garage, a floor thickness of four inches is appropriate. If you are parking bigger vehicles and even heavy trucks, you need more than four inches of thickness.
Preferably go for floors with a minimum of six inches in thickness. This will boost its resilience, avoiding cracking when those heavy trucks are parked on it. Note that if you are going to park those heavy-duty trucks in a garage, the floor must be well sealed and treated.
Certainly, you can’t ignore the cost of concrete or the labor you are going to use. This cost (aside from your labor and building permit expenditures) cuts across what you would pay for the concrete and its transportation and even material overage.
Given these considerations, you can spend anywhere from $580 to $630 on a 400-square foot concrete slab. This is the equivalent of approximately $1.50 per square foot.
Your labor cost depends mainly on where you are building as said. High-end states like California will cost you more compared to low-end states like Georgia. For example, labor cost for a 400-square foot concrete slab (the type you use for your two-car garages) in San Francisco would cost you about $2.22 per square footage. But if you were in Atlanta, you may not spend more than $1.58 per square footage (on labor cost) on that very 400-square foot concrete slab.
Are Brick Foundations Bad?
Brick foundations are not as bad as they may appear. If you can competently build your brick foundation, it can serve you for over 50 years, depending on how you use it. The prevalent conditions that determine the sustainability of brick foundations include the soil and weather conditions. If you experience flooding disasters, it will admittedly affect your brick foundation.
Vertical cracks are a common nightmare with brick foundations
Vertical cracks are a common challenge with brick foundations. Once you start noticing the emergence of such breaks in your brick, it is a strong signal that your foundation is already developing severe issues. In most cases, such vertical cracks are caused by shifting soil. Such soil movement provokes house settling. If you don’t pay immediate and tangible attention to it, the cracks would quickly escalate.
With widening cracks, your garage becomes more susceptible to flooding. It doesn’t end there; such flooding encourages rapid mold growth all across your basement, spreading to the walls of your house.
Vertical cracks are common in brick foundations because of the pressure pelting the mortar. You will agree this could cause the formation of cracks. It degenerates even further with a rotation of the foundation walls. Bricks, despite their impressive strength and resilience, would struggle to survive the pressure and resultant sheer force.
There is also the propensity to horizontal cracks with brick foundations
Horizontal cracks are not uncommon with brick foundations. Just as the name suggests, these cracks run longitudinally across the bricks. Horizontal cracks even spell more danger than vertical cracks.
This is why you should pay more urgent attention to horizontal cracks in your brick foundation. Horizontal cracks can form if the walls are receiving excessive pressure from the soil bounding your home. This would eventually force the walls into caving in.
Lastly, there are step-style cracks
These cracks resemble climbing stairs. This kind of breaks can be attributed to soil movement as well. Step-style cracks are prevalent in areas where the soil has poor drainage. This is seen when the soil is highly expansible, and the particles are loosely packed. You will suffer this type of cracks if you have inappropriately back-filled the space around the basement.
How Much Does It Cost to Pour one car Garage?
The size of your garage is most times decided by the number of cars it will be accommodating. If you are pouring a one-car garage size, you should be looking at a garage dimension of about 16′ x 24′ (going by the standard). This will cost you approximately $8,000.
This is depending on if you are going for an attached one-car garage or a detached one-car garage. Keep in mind that it will cost you an average $49 for every square foot of your garage consequent to the type of finishing you want or the dimension.
You can go for a 12’x24′ garage size for a one-car garage which will take about 288 square feet. This will cost you about $14,000. Alternatively, you can choose a 14’x28′ garage size, which is about 392 square feet. This goes for about $19,200. Detached garages are more expensive when compared to attached garages.
How Much Does It Cost to Build a two-car Garage?
Basically, if you are going for the traditional two-car garage with dimensions of 24’x32′, you would spend barely $12,700. This means you are not paying up to $17/SF if you go for a two-car garage of about 765 square feet. If you choose to push it further to the 30 x 36 modular, you will spend around $20,000. This can be adequately capacious to store many things.
There is also a viable alternative in the attic two-car garage, which comes with a complete stairway for enhanced attic accessibility. This is relatively more expensive and could cost over $27,000 for a 28’x32′ garage.
The cost of installation depends on where you are building. If you are installing a 400-square-foot slab in San Francisco, you can expect to spend as high as $2.30/SF in labor cost only. If you were going for an attached two-car garage, you might spend above $14,000.
In Atlanta, you would spend far less on labor cost as such a 400-square-foot installation could cost you about $1.53 in labor cost.
How Much Does a three-car Garage Cost?
If you have more than two cars, you obviously need a bigger garage to give you and your more guests more parking expanse without having to clog the driveway with your cars. This brings us to three-car garages. More than this, a 3-car garage will significantly push up the resale value of your home hence a worthy investment.
A basic 36′ x 24′ three-car garage of 864 feet can cost you over $42,000 depending on if it is an attached or detached garage. Aside from this, the driveway paving and your taste of interior finishing will also contribute to the cost of the garage as well.
If you want to build an accommodating and ideal 3-car garage, then the garage should be at least 32 ft wide with a depth of 22 ft. If you want more flexibility, you can go for three-car garage designs of 40×30 or lesser (depending on your budget) at 38 X 26.
Mike Zhang. Founder of FamilyLifeShare