How to Build a Garage: Save Thousands by Building a DIY Garage vs. Hiring a Contractor

October 12, 2021 by No Comments

Learning how to build a garage is not as overwhelming as you might expect, well, at least for freestanding structures. Homeowners who build their own garage can save thousands by hiring a builder who, in many cases, will outsource to the same construction crews that you may hire. Or if you’re feeling adventurous, or just thrifty, you can invite friends over for a few beers over the weekend and put them to work.

There are many elements to consider during the initial planning stage, such as:

Garage Size – One-car, two-car, or even three-car garages can be designed in various sizes, but the lot and the owner’s budget are generally the limiting factors. Local building codes vary, but typically a structure should not encroach within eight feet of property lines in rural areas and zero to four feet in city limits. Detached garages should also be away from other buildings by a minimum of eight feet, but this should be confirmed with the building’s local offices, as omens vary. An important consideration is the roof overhang. Eave and gable overhangs are typically 12 “to 24” (although less than 12 “is common in windy areas) and should be considered when determining the size and location of the building.

One method of determining the perfect size is to add 12 ‘to 15’ width for each vehicle. If you plan to use the interior walls on the sides for storage, this will require another two feet of width per side. Length should be a minimum of 22 ‘and add four to ten feet for a workbench and storage. A two car garage could be calculated as 2 x 12 ‘+ 4’ for storage along each wall = 28 ‘x 22’ long without a workbench. Common sizes include:

1. A car: Common garage sizes include 12 ‘x 24’, 14 ‘x 24’, and 16 ‘x 24’. A length of twenty-four feet is practically the minimum if you have a full-size truck, and even with a small or midsize car there will be little room for maneuver at twenty or twenty-two feet.

2. Two cars: The most common garage size in many states and provinces is 24 ‘x 24’ because many building codes require a designed drawing and two inspections by a structural engineer for larger floating (monolithic) concrete slabs. than this size. If space is at a premium and the two cars are small to medium in size, a width of 20 ‘may be adequate, but it is certainly not comfortable.

3. Three cars: There are many sizes of three car garages because there is more room for numerous designs and homeowners often have larger budgets when considering these larger construction projects. Common sizes are 36 ‘- 42’ wide by 26 ‘- 30’ long.

Foundation: Floating slab (monolithic) and slab with frost wall are the two most common foundation options. Floating slab is less expensive and easier to build, but often requires an engineering drawing and two inspections for larger concrete slabs (i.e. 24 ‘x 24’). In cold climates, many contractors install 2.5 “foundation foam under concrete to reduce uplift during freeze / thaw events. Floating slabs designed in cold climates generally require this with an additional two feet extending around the perimeter of the slab. .

Adding 6 ‘x 6’ # 10 wire mesh to the slab is an inexpensive method of increasing the strength of the floor and reducing cracking of the concrete. Most contractors install floating slabs with a thickened concrete perimeter 12 “to 16” thick around the outer 16 “to 24” of the perimeter. Add two rows of rebar n. 4 will increase the edges. Concrete strength should be a minimum of 3000 psi and many contractors use 4000 and 4500 psi as the additional cost is minimal. Another consideration is the order of concrete with fiber mesh and macrosynthetic fiber used for secondary reinforcement of the concrete. Local concrete suppliers can provide the costs of adding this to concrete. Slab thickness depends on the strength of the concrete and reinforcement designs, however a good rule of thumb is to pour a 4 “or thicker slab.

The minimum depth of the ice wall is determined by local building codes and is typically 48 “in cold climates and 36” in more moderate areas. Once the trench is dug, a footing approximately 12 “wide by 8” thick is formed and poured and a keyway is etched along the footing to prevent movement of the concrete wall. The frost wall is formed and poured over the base and anchor bolts are installed to attach the walls to the base. The concrete slab is then poured to the designed thickness. Obviously, this foundation system requires more time and expense.

Wall Construction – If the garage is to be insulated now or possibly in the future, the size of the wall studs is important, as the 2 “x 6” studs allow for more insulation that can meet the requirements of the building code (for apartment garages) than 2 “. x 4” studs. Of course, the 2 “x 6” studs are stronger, resulting in a more structural-sounding building.

Wall Height – Walls are generally 8 ‘, but 9’ and 10 ‘walls are common. In downtown areas, there is often a height restriction on structures, such as less than 16 ‘to the peak of the roof based on the average height of the four corners measuring at grade. This means that you can get a bit more height if the garage is located on a bench with a concrete curb or retaining wall at this end and is filled to the top of the retaining wall. Another method to maximize height in these areas is to pour a 12 “concrete curb around the perimeter of the concrete slab and backfill the soil to the top of the curb and level away from the structure. This method can gain 12” of height while still complying with the Height Restrictions (please confirm this will affect the local building offices before implementing this strategy).

Garage Door Placement: Garage doors can be on the gable or eaves side. Some things to consider:

1. The layout of the existing home can dictate the direction of the roof line. One method to help visualize this is to take a photograph of the house and include the area where the garage will be built. Print two copies of the image and draw by hand in the garage using the gable and eaves options.

2. If the garage will be built in cold weather, the gable end garage doors are better designed as snow and ice will slide off the eaves end.

3. Flexibility with gable end garage doors allows height for future parking area.

Roof Style – Often times the roof style is dictated by the existing house, for example if the house has a hipped roof this would be a good option for the garage. If it is a DIY project and the owner is building the garage, it should be noted that it is more difficult to build a hipped roof than to install standard trusses. The slope of the roof must also be taken into account and often must match the existing house. A roof pitch of less than 4/12 (rises 4 “for every 12” of travel or length) is not recommended due to the increased potential for water leakage. Steeper ceilings with certain lattice designs can allow for storage, loft, or even apartments above the main level. The most common roof trusses for garage roof design include:

1. Standard Fink – This is the most common residential truss.

2. Double fink – designed to handle heavy loads for higher snow load requirements.

3. Attic: Common for designs that allow storage above the main floor. Access can be by ladders or folding ladders in the attic and the available option may be determined by local building codes.

4. Scissor – This option provides cathedral ceilings (vaulted) that provide more interior ceiling height. For example, a 24 ‘x 24’ garage with an 8/12 pitch may have a ceiling height of 12 ‘in the center and 8’ at the wall. This system is generally compared to building with regular fin trusses and taller walls.

If it’s a DIY garage project, don’t forget to order two gable trusses for each gable end. Otherwise, two regular trusses will require wood filler to join the siding and siding (not to mention the building inspector may fail the structure inspection. If you are insulating the roof, consider ordering “raised heel” trusses for allow adequate insulation between the top wall plate and the ceiling This is the only way to meet many attic insulation level requirements (ie R40).

Garage Blueprints – Once the decisions are made on the items above, it’s time to get the garage blueprints for the builder and building permit application. It’s important to get good quality garage plans that are easy to follow, accurate, and provide a bill of materials (well, a bill of materials is not important, but it will certainly save a lot of time). There are several websites that offer garage plans created by dozens and hundreds of different companies, so consistency and quality control are something to consider. There are a couple of companies that do their own in-house copywriting and an internet search should find these companies. Another option is to hire a local draftsman to create the garage plans.

Lot Plan (plan): The building compliance department will require a drawing showing (site plan) the lot with existing structures, proposed structure, and property lines with measurements indicating distances between lines of property and structures. This can be a hand-drawn diagram of a marked copy of the plan / plan. The building department may require a survey to confirm the accuracy of the measurements for the precise garage location requirements.

Building Permit – Schedule an appointment to meet with a building inspector to discuss the project and present the garage plans, bill of materials, and site plan to the building department. A building permit can be issued at this time or the building inspector will need a few days to a couple of weeks to review the documents.

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