Installing sliding patio doors: a step-by-step guide

Installing a sliding patio door in your home is an amazing way to fill your outdoor home or office with sunlight and help bring the outdoors in.

While this can be a tedious job, it’s totally doable, especially if you’re already a handy person and confident in DIY – maybe you’ve hung a door before. If you are installing interior sliding doors, you have a little more room for error; even if something is not quite straight, although it is annoying, it will not impact the security of the house.

Exterior doors are another story and you have to put everything in place to avoid humidity, drafts and the risk of break-ins. Also consider where you install the doors – it is advisable not to install them at the front of the house as this could make you more vulnerable to break-ins. They are, however, a great addition to the space for that harmonious indoor-outdoor living ambiance.

Follow these steps below to install your sliding doors and let the light in!

Difficulty: Medium, tedious and you’ll need both of you, so bring in a patient buddy

Approximate cost: Varies depending on the material (wood, aluminum, uPVC) and if they are pre-hung. Here we have used a pre-hung PVC door which you can expect to pay from $1000 (or around £700 in the UK) for. They are the easiest to install as they come in as a single unit. You won’t need to assemble the frame before installing it on your wall.

Time: Leave aside an afternoon


A front shot of the backyard garden outbuilding with a white door and windows before the sliding door was installed

(Image credit: Kate Sandhu)

We have an outbuilding which has been transformed into a garden office. We wanted to make the space more pleasant, by increasing the natural light.

Preparing to install doors

When shopping for doors, you need to know the exact size of opening the door needs to fill. If you create this opening (per step 1, below) you have more flexibility in choosing doors, if there is already an opening, use a tape measure to measure the full width of the hole. Measure from stud to stud.

  • Measure the width and height of the opening. Write down these measurements so you can refer to them when shopping for a door.
  • Before measuring, be sure to remove any boards or shims that may have been added to fit the old door.

How to install a sliding door

You can buy a sliding glass door online (check reviews) or at a home supply store such as Home Depot. (opens in a new tab)if you go to the store, be sure to bring your tape measure with you.

1. Prepare the space for the door

A male worker inside a garden outhouse removing bricks and cinder blocks to make room for the installation of sliding doors

(Image credit: Kate Sandhu)

Make room for the door in the wall or remove the old door. If you are creating a gap from a wall, you will need to remove bricks or cinder blocks using a drill and hammer, then fill in any masonry as needed, making sure the hole is as close as possible of the size of the desired doors (we will cover any minor adjustments needed in the following steps).

If you are removing an old door, remove the set screws at the bottom of the door, lift the door rollers and slide the door out by tilting it forward. Once it is out, pry the frame out using a crowbar to pry it out of the hole.

2. Clear the space and make sure the gap is accurate

A person wearing a black smartwatch using a screwdriver to install a sliding door

(Image credit: Kate Sandhu)

You’re likely to have a bunch of nails, screws, and dirt in the space if you’ve removed a door or created a new space for one, so you need to clean and adjust the opening. This means getting rid of leftover nails or torn hardware. You may also need to adjust the opening if it’s not quite the right size.

Use a spirit level to make sure the top, bottom, and side frames of the opening area are all level. If some are not level, you can use a shim (a thin piece of wood) to even out the door frame. If the frame is slightly too large for the sliding door you purchased, nail one or more strips of 1 x 3 centimeter plywood to adjust the size of the opening to the correct size.

3. Seal and install the door

A worker installing a sliding door for a backyard garden outhouse

(Image credit: Kate Sandhu)

Add flashing to protect against water damage before installing the door. Flashing is a type of waterproof tape that protects the door frame and bottom edges of the sliding glass door from water damage and prevents water from seeping through the edges of the door.

Apply one coat along the bottom threshold of the door frame, letting the tape hang over the outside edge of the frame so you can fold the tape over and press it to the outside side, then apply about 40 centimeters from each side to from the ground. . Door installation is a two-person job; have a friend help you lift and carry the door inside the house and push it into position in the large opening. Make sure you position it the right way around so you don’t install it upside down, check that the lock is on the right side.

Use a spirit level to check that it is perfectly straight, this is the most important step in the process! Once you’re sure everything is level, screw the frame into place according to the manufacturer’s instructions, making sure to check where the screws need to be before securing everything. If you have any gaps that worry you, you can put fiberglass insulation in those gaps. This will prevent your home from losing heat around the frame.

4. Seal the door and remove the protective covering

A person holding waterproof sealant and applying around a sliding door

(Image credit: Kate Sandhu)

Use a waterproof sealant on the sides to keep away any water that might seep around the door frame. Check again for any holes, cracks or gaps and make sure it is fully sealed and sealed. Once dry, you should be good to go! Remove any tape or protective covering and dress the area with curtains, blinds or other door furniture, then sit back and enjoy!


An exterior shot of the backyard with a garden outhouse, wooden garden table and chairs and a striped parasol

(Image credit: Kate Sandhu)

We chose black door frames to match the black brick of our outbuilding. We now get lots of light in the space and can open it out on hot days for a cool breeze.

Do sliding patio doors slide in or out?

This type of patio door must always be installed in such a way that the door slides inside the fixed frame. The doors are designed this way so that they are more secure.

When you have finished installing your doors, consider this sliding element before placing the furniture. The doors won’t protrude far into the room, but you can’t place furniture too close to the mechanisms or you won’t be able to open them. Still, they’re a good option where space is tight because you don’t have to let them open.

About Margie Peters

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