Can I Build a Shed Attached to a Garage?

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Many homeowners have often though about building a shed that’s attached to their garage, this may be an option for some and its also less costly. You will need to consult with your local building authority to find out what your options are.

It’s certainly possible to build a shed attached to a garage. It gives you the storage capabilities of a shed while saving you some building, as one wall already exists. It also gives you added stability with the shed being attached to a larger building. You can build it onto the side of your garage or onto the back, which will keep it hidden.

Attached sheds can range from being a fully enclosed shed to a simple woodshed or lean-to, or even just an open roof extension to house a few things. You can build it yourself or buy a kit. There are some specially made for attaching to an existing building.

However, the first thing you should do is to check with your local building authority. Some zoning regulations don’t allow outbuildings to be attached to the house. You’ll probably need a building permit at any rate. If you live in a homeowner’s association, you’ll need to check with them as well.

Once you decide what kind of building you want to add, you need to plan your shed so that it blends in with the look of the rest of the house. You don’t want it to stick out like a sore thumb or look like it was just plugged on like some odd piece of a Mr. Potato Head.

This is especially important in a homeowner’s association, as they usually have more of an emphasis on appearances and continuity. If you live in an area with no building restrictions, you can just put up a few posts and corrugated metal sheets for a roof. Just remember that when it comes time to sell the house, potential buyers may not be attracted to a nice, modern home with a shed addition that looks like it was rescued from an old farm.

How to Attach the Roof and Walls?

Many attached sheds aren’t quite as complicated as the stand-alone sheds. While you can build a doorway directly from the side or back of your garage into the shed, it’s much easier to just have the shed have its own outside entrance. Cutting through your garage wall will be quite a project, especially if you have electricity in the garage. You’ll need an outer door to the shed anyway if you plan to keep wheeled items such as mowers or tillers inside.

Some people choose to just leave the front of the attached shed completely open to drive in mowers and ATVs, both the front and back, or just have it completely open on all three sides. You can even put a door in the front but leave the back completely open. This will fool potential thieves into thinking it’s a fully enclosed shed while leaving you plenty of room to drive in your yard vehicles easily.

As far as siding, it would be best to use the same type of siding as on the rest of the house, or at least the same as the garage if it is different from the house. If this is not feasible, choose a siding that you can paint the same color as the rest of the house.

Usually, a 2 x 4 is attached flat to the garage wall a few inches above the top of the outer wall posts. This board is nailed to the studs of the garage wall. The extra height is designed to create the roof slope. Rafters are fastened to the top of this board and then to a cap board nailed to the post tops.

How Much Slope Should the Roof Have?

The minimum slope should be figured on allowing at least a quarter inch per foot. This measurement will satisfy many building codes, but it’s best to get that information from your local building inspector before you start. Every municipality and location has its own rules.

Building your shed roof with the same slope as the garage roof will really make it blend in nicely. Using the same type of roofing as the rest of the house will also tie the building in nicely and keep it from being an eyesore.

What Kind of Foundation is Needed?

If you have an enclosed garage, you probably have a concrete slab floor or foundation for that. It would be a good idea to do the same for your shed to keep the floor on the same level. Even if you choose not to construct a walk-through from the garage, your shed will look much better and integrate better with the overall structure of the house if it is on the same level. You can also form the foundation from concrete blocks. If you are just building a simple open lean-to that is basically a roof extension, you won’t really need a floor.

How Do You Make a Floor?

You can use the same flooring you would in a detached shed, ranging from a concrete slab to concrete blocks or other choices. If this is going to be basically rough storage for your outdoor tools and equipment, you might investigate plastic shed bases. These are made of squares of plastic formed into a grid that lock together to make whatever size floor you need.

These are used on many types of smaller sheds. It would be a good idea to extend the gravel outward about a foot around the exterior of the shed to help water running off the roof drain away.

Be sure to level and smooth your dirt, then place landscaping fabric or a vapor barrier over the dirt. Some plastic shed base kits come with a membrane for this included. Lay the blocks in place and attach them according to instructions. For extra strength, you can pour pea gravel or small aggregate into the grids. Backfill around the edges.

How Do You Build a Shed onto a Garage?

There are many ways to do this; we’ll look at a relatively uncomplicated construction that will still do the job. Of course, you can use whatever siding and roofing you wish. For tools, you’ll need a tape measure and level, a post hole digger, concrete, hammer and framing nails, a few concrete nails, metal flashing, plywood, corrugated roofing with roofing screws equipped with washers for waterproofing, and a circular saw.

For lumber, you’ll need 4 x 4″ posts, 2 x 4″ lumber 1 x 4″ sheathing boards, 1 x 2″ batten boards, a 2 x 6″ board for a door header, and pressure-treated plywood rated for exterior use for siding. You’ll also need 4 x 4 x 8″ concrete blocks for the flooring.

Layout the dimensions with your tape measure along the existing garage wall. Mark spots for posts at the corners and every eight feet in between. Make sure your space is square. Use the post hole digger for your posts, setting them in concrete. Make sure they are all straight and plumb.

Posts should be set into the ground about a third of the total length. For instance, 12-foot posts need to be buried three feet deep. This will give you a nine-foot roof with an eight-foot ceiling interior.

Dig out your flooring eight inches deep and level. Lay some landscape fabric into the depression and spread it up and over the edges of the dig all around. Then lay down three inches of gravel or aggregate, tamping it down evenly. Spread an inch of sand over this. Set your blocks into the sand.

Cut half blocks to allow you to stagger the block arrangement and fit them around the posts. Make sure they are all level. Spread dry cement over the blocks and sweep it into all the cracks between the blocks. Dampen it with a garden hose and let it set for a firm floor.

Nail a 2 x 4″ board horizontally on the garage wall a few inches higher than the posts according to the slope you want. Nail it to the garage wall studs. Nail 2 x 4s on top of the posts and others vertically with the flat side to the garage wall to match the posts. Attach bracing boards to connect the posts and wall eight feet above the flooring.

These will be your ceiling joists. Attach rafter braces to the top of the horizontal wallboard and to the post cap board to form your roof slope, leaving enough length at the outer edge for your overhang.

Your 1 x 4 sheathing strips go on the tops, bottoms and centers of the walls for your siding. You can use corrugated metal or fiberglass for a roof or install plywood for roof sheathing if you plan to use shingles. Make sure you install metal flashing that goes up the wall and over the roof. Use a clear sealant to prevent leaks. You absolutely don’t want water to seep between your shed addition and garage wall. Cover your walls with plywood.

The doorway is made of 2 x 4 studs for the outer frame and a 2 x 6 header board. Cut your plywood to fit around it. Additional bracing may be added if needed. A horizontal base plate should be nailed to the concrete blocks. Finish off your shed by painting the exterior to match your home’s color.


If you have the room and it’s allowed in your locale, building an attached shed is a great way to add storage while saving you a lot of the work involved in building a free-standing shed. Just take care to make it look integrated as possible to the rest of the home, and it will be an asset to the home’s value as well as a very useful addition.

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