What mistakes do people make when building a garage?

Johannes van Graan Johannes van Graan
Garden Studio Man cave, Samuel Kendall Associates Limited Samuel Kendall Associates Limited
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Building a garage might sound like a huge (if not impossible) task, but rest assured that it is something that can be completed by someone with technical- and DIY experience. However, we must recommend that you take advantage of free online resources and research the project thoroughly before you attempt to build your garage, especially the foundation as that is one of the more important aspects. 

The benefits of researching are that you can learn from other people and sidestep their mistakes – which is exactly what we intend to help you out with today.

1. Remember to notify authorities

Garden Studio Man cave, Samuel Kendall Associates Limited Samuel Kendall Associates Limited

In your excitement to kick-start that garage of yours, don’t forget to notify the relevant authorities to obtain the necessary permits. 

With no permits, town- or city councils can stop your project and even require already built structures to be torn down – a huge waste of time, money, resources and patience, obviously.

2. Ensure the foundation walls go deep enough

Should those foundation walls not go deep enough into the ground, it could cause the foundation to sink deeper over time and cause various structural issues. Besides, wouldn’t you want a space that houses your expensive car to have a strong and secure foundation?

Bear in mind that the concrete also has to be thick enough to support the garage, as seen here. And don’t forget that the foundation needs to be perfectly flat, otherwise your measurements will be off and your end result will be a crooked garage!

3. Plan properly

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Consider the need for drainage, electrical outlets, plumbing, and HVAC (heating, ventilation and air conditioning) prior to pouring that foundation. And before you start to build on top of that foundation, make sure the concrete has set properly. 

Foundation vents might also be required, depending on where you live. The vents are needed for various reasons, especially to allow the air to move so that any moisture will dry. Without vents, the garage foundation can become moist, which will inhibit the growth of mould and mildew and break down the concrete.

4. More things to remember

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• Make sure you dig a few extra centimetres around the slab when digging holes for the footings to allow room for the vapour/sand barrier.  

• The rebar should be between 5 and 7 cm away from the ground, on all sides, when running it horizontally along the bottom of the footings.  

• Put the foundation bolts into place before the concrete hardens, which will be used later to hold sill plates.  

• Use an oil spray on the concrete form boards which will make the removal of the boards once the concrete foundation hardens much easier.

5. The warning signs: Cracks in floors and walls

When your garage foundation shows signs of problems, urgent repair work may be in order.

Diagonal cracks that appear around the corners of windows and doors (as well as between the floor and wall) are a clear sign of foundational problems. Floor cracks may be caused by expansion of soils underneath the foundation. This settlement pushes parts of the foundation upwards so that the height exceeds the initial elevation in some areas. The stress eventually creates cracks on the garage floor and walls. 

Consistently high temperatures may also cause a moisture imbalance in the soil. As the soil pulls away from the foundation, the resultant stress creates cracks in the garage floor and walls. What you're after is nice smooth surfaces, like those shown here.

6. The warning signs: Uneven floors

Slopes on your garage floor are a sure indication of problems with the foundation. 

Trees close to the garage may play a role in distortion of the garage floor. Roots draw up much of the moisture from the ground, which causes the shrinkage of soil. 

This leads to an uneven settlement of the home, which can cause the floor to slope in the garage.

7. The warning signs: Wall rotation


You may have noticed that your garage walls rotate outwards. This is usually linked to differential settlement, whereby the foundation settles unevenly. 

Soil properties and quality of construction further impact the way in which a house settles.

8. The warning signs: Crooked windows


When garage windows don’t align properly or get stuck, it may be because of foundation problems. 

Bad drainage can lead to excessive moisture in the soils around the garage. This causes expansive soils, which are associated with uneven settlement.

9. The warning signs: Wall- and door separation

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A weak foundation could also lead to walls separating from the door, windows or ceiling in your garage. Sometimes gaps occur between the garage door and pavement on either side of the door. The garage door may also fail to open and close properly. This indicates foundation problems. 

Poor site preparation may contribute to a weak garage foundation. If the site of your home wasn’t well graded, it opens the way for future foundation problems. 

In addition to reducing the energy-efficiency of your home, gaps around the garage door and –windows could also allow insects and rodents access into your house.

10. Take care in hiring a repair contractor

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Repairing a garage foundation is usually best left to the professionals

But regardless of where you begin the search for an expert contractor, be sure to check out their references. And always check that the quote includes all the costs of the materials and labour before anything is agreed to. 

Did your garage construction go off without a hitch? Now let’s see: 7 steps to the most organised garage on your street.

Have ever attempted to build a garage?

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