Extending your garage can add value to your home, but it is not an easy task. Ensure that a good job is done by planning carefully and using sound workmanship. The extended garage should match the existing structure. If the work screams "addition," prospective buyers could perceive the work as shoddy.
Design your extended garage. You will need to look closely at the existing structure to ensure that your design matches with regards to roof pitch, brick colour, and proportion. You may feel more comfortable employing an architect to design the extension for you.
Use a shovel to excavate the footing for your extended garage. Dig to a depth of at least 15 cm (6 inches), and use the timber to support the sides of the excavation. Lay the steel mesh in the bottom of the excavated area and pour the concrete over the mesh, covering it.
Use another piece of timber to tamp the concrete -- that is, to strike it repeatedly to flatten it, make it level and remove any air bubbles. You will need a helper for this.
Build your external and internal walls using block work, remembering to leave openings for windows, doors and the additional garage door at the front of the building.
Carefully take down the old external wall of the garage (now an internal wall) using a sledge hammer. Erect steel columns to hold the weight of the extended roof.
Bed a piece of timber to the top of your new block work walls as a wall plate, and attach the trusses to this, remembering to brace them to each other. Fix any guttering and downpipes that you require, and build up brickwork outside the block work to match your existing garage.
Nail shingles or roof tiles to your new roof. Fix windows and doors to your structure that match the existing windows. Hang the new garage doors in accordance with the manufacturer's instructions; you can choose between roll-up or 'up-and-over' garage doors, depending on your preference and what you already have.
If you are unsure of your construction skills, you may wish to employ a contractor.