Garage Additions

Attached or detached, and what each one asks of the lot

The first question is where the garage can go. Every town sets setbacks from the property lines, and a garage that seems to fit by eye can land a few feet inside the line once the lot is measured. Septic tanks and leach fields have their own required distances, and on plenty of lots the leach field sits right where the owner pictured the driveway. We look at the plot plan and the site before anyone draws a garage.

An attached garage shares a wall and often a roof line with the house. It keeps you dry between the car and the kitchen, and it reads as part of the house from the street, so the roof pitch, trim and siding have to match. It also brings the fire separation rules into the job. A detached garage avoids most of that and gives you more choice in placement and size, but it needs its own power run, a longer driveway and, if you want heat or water, its own utilities.

Neither is right for every property. We will tell you what each one means on your lot, including what it does to the yard and the drainage, and you decide.

Size is worth a second look as well. Today's trucks and SUVs are longer and wider than the cars many older garages were drawn around, and a garage that fits the car but not the open doors, the bikes and the snow blower is one you will park beside rather than in. We measure what you actually own and plan the depth and width around it.

Frost walls, the slab and where the water goes

A garage carries cars, snow melt and road salt, so the base matters. In Massachusetts the footings go below frost depth, commonly about four feet, and a garage usually sits on frost walls with a concrete slab poured inside them. A slab set on poorly compacted fill will settle and crack, and the cracks will run right where you park.

The slab is pitched toward the overhead door so meltwater runs out rather than pooling against the house wall. Outside, the finished grade has to fall away from the garage, and on attached garages we look hard at where the roof water from both buildings ends up. A new roof can double the water landing at one corner of the house, and that corner is usually where the basement leaks.

If you want a floor drain, a heated slab or a workshop sink, that is decided before the pour. Changing your mind after the concrete is down means cutting it.

Concrete also needs the weather on its side. A slab poured into a cold snap without protection can be weakened at the surface, and road salt finds that weakness within a couple of winters. We plan pours around the forecast and protect the slab as it cures, and if the weather forces a delay, you hear about it that morning.

A slab set on poorly compacted fill will settle and crack, and the cracks will run right where you park.

Door openings, headers and the room above

An overhead door is a wide hole in a bearing wall. A two-car opening needs a header sized for the span and for whatever sits above it: a roof alone, a roof with snow, or a whole room. On larger openings that header is often an engineered beam, and it is drawn and specified before framing starts, not picked off a lumber rack on the day.

Many owners decide they want space over the garage once they see how much roof is going up. A storage loft is one thing. A finished room is another: the floor framing has to carry living loads, the stair has to meet code, and the room needs heat, insulation and its own egress window. The garage ceiling below it becomes part of the fire separation, which changes what gets hung there.

If there is any chance you will want a room above in the next few years, tell us now. Framing the floor and roof for it at the start is far less trouble than opening a finished garage roof later.

The wall between the garage and the house

The code treats the wall and ceiling between an attached garage and the house as a fire separation. In plain terms, that means gypsum board on the garage side of the shared walls, heavier board on the garage ceiling when there is a room above, and a door into the house that is solid or fire rated and fits tight. Penetrations through that wall, such as wires or ducts, are sealed so smoke cannot travel through them.

Fumes are the other reason. Car exhaust and stored fuel should never find a path into the house, which is why ducts serving the house do not open into the garage and why we air-seal that common wall as carefully as an exterior one. Where a garage is heated, the heat source is chosen with the same concern in mind.

On older houses the existing wall that becomes the common wall often needs work. It may be an old exterior wall with no sheathing, or clapboard over balloon framing. We open it, show you what is there, and build the separation properly instead of covering it.

Scope, permits and the days on site

The job starts with a walkthrough and a look at your plot plan. You get a written scope covering the foundation, slab, framing, door package, roofing, siding, electrical and anything optional such as a loft or a room above. That scope is the basis for the price, and changes are written up and agreed before the work they affect.

Permits come through the town's building department under 780 CMR, with Steve's Construction Supervisor License on the structural work and licensed electricians for the wiring. Inspections typically come at footings and foundation, framing, rough electrical and final, with insulation added if the space is heated. You get a call or a message before each one and a word on how it went.

Excavation and concrete trucks mean a busy stretch in the driveway. We tell you when they are coming, keep a lane open when we can, and leave the site picked up each night.

On a detached garage, the trench for the power line is planned along with the driveway work so the yard is dug once, not twice.

See the rest of our additions work, or browse the gallery for rooms we have finished.