A sliding patio door trades opening width for floor space. On a 72 inch opening you get roughly 32 to 34 inches of clear walkway, once the fixed panel, the interlock and the frame have taken their share. In return you keep the 3 feet of room a hinged door would have swung through. Whether that is a good trade depends entirely on what is standing in front of the door.
This guide covers what a slider gives you when it is open, and where it beats a French pair. Then what wears out and why, how one gets forced, and the two numbers to compare on a quote. When I price a patio door job the opening decides most of it, not the door. We fit sliding patio door replacement across the St. Louis metro, so most of this comes off jobs rather than a brochure.
What You Actually Get When It Is Open
The clear opening is the figure that decides whether a slider suits your room, and almost nobody puts a number on it.
A two panel slider has one fixed panel and one that moves. The moving panel can only travel as far as the fixed one, so the most you ever open is half the width, and you do not even get all of that. The frame takes some at the jamb, and the interlock stile where the two panels meet takes more.
| Opening width | Roughly what opens, two panel slider | Roughly what opens, French pair |
|---|---|---|
| 60 inches, a 5 foot door | 26 to 28 inches | 48 to 50 inches |
| 72 inches, a 6 foot door | 32 to 34 inches | 58 to 60 inches |
| 96 inches, an 8 foot door | 44 to 46 inches | 80 to 82 inches |
Standard heights are 80 inches, and 96 inches is available as an upgrade. Frame depth is usually 4 9/16 inches for a 2×4 wall and 6 9/16 for a 2×6.
Thirty two inches is also the clear width a wheelchair needs. A 5 foot door opens 26 to 28 inches, so it does not make that. A 6 foot one just does.
3 panel and 4 panel sliders change this. On a 3 panel door two of the three can be made to move, so a 12 foot opening can clear about 8 feet. That is the configuration to ask about if the width is what you are after and the wall can take it.
Sliding or French
Take the table above into the room and walk it. That settles it faster than any list of benefits.
| If this is true of your room | Pick |
|---|---|
| A sofa, table or bed sits within 3 feet of the opening | Sliding |
| You carry furniture, coolers or a grill through it | French |
| The wall outside is narrow and a swinging leaf would foul it | Sliding |
| You want the opening to feel like a doorway, not a gap | French |
| Somebody in the house has weak hands or wrists | Sliding, with good rollers |
| You want the widest possible clear opening | French, or a three panel slider |
There is more on the hinged option on our French doors page, and the wider view of every exterior door in the types of exterior doors guide.
What a Slider Is Genuinely Good At
A sliding patio door earns its place in five specific ways, and they are worth separating from the marketing.
- It gives back the swing. A hinged leaf needs about 3 feet of clear floor. A slider needs none, which is why it survives in rooms a French pair cannot fit.
- It holds more glass for the same wall. Two big panes instead of two stiles and an astragal, so more daylight and a cleaner view.
- It takes the least effort to operate, as long as the rollers are right. That matters more than people expect on a door used several times a day.
- Nothing slams. A gust cannot catch it and swing it shut, which is worth something with small children and a windy deck.
- The screen stays out of the way. A sliding screen runs on its own track rather than hanging off the frame.
What a slider is not is a wider opening. That is the trade, and any list of advantages that leaves it out is selling rather than explaining.
What Wears Out, and Why
The panel does not slide on the track. It rides on a pair of tandem rollers set into the bottom rail, and those 4 small wheels carry the whole weight of an insulated glass unit every time it moves. A 36 inch by 80 inch double glazed panel is heavy, and all of it goes through those wheels.
Grit is what kills them. Dirt, sand and pet hair collect in the lower track, get rolled flat under the wheels, and grind a flat spot into them. The panel starts to drag. Somebody puts a shoulder into it. That is the moment the roller housing cracks, and from then on it only gets worse.
Two habits stop nearly all of it, and you can do both yourself. Vacuum the lower track a few times a year, and if it needs lubricant use a dry one. Oil and grease hold grit against the wheel, so they make the problem they were meant to fix.
If yours already drags, look for two plugs at the bottom edge of the moving panel. Behind them are the roller adjustment screws, and a quarter turn each is often the whole repair. If that does not do it the rollers are worn, and that is a repair rather than a replacement, which is not work we take on. A glass and door repair outfit will do it in an hour.
How a Sliding Door Actually Gets Opened
Not by picking the latch. The common method is lifting the moving panel up into the head track far enough that the bottom clears the sill, then swinging the bottom out. On an older door with worn rollers there is enough vertical play to do it in seconds, and the latch never comes into it.
Three things stop it, and they stack:
- Anti-lift blocks in the head track, or a pair of screws driven into it, so the panel cannot rise far enough to clear the sill. Cheapest fix there is.
- A secondary lock low on the frame, a foot bolt or a pin through the frame into the panel, which resists in a different direction from the latch.
- Laminated glass, which holds together when it breaks. A multi-point latch is worth having, but glass is the panel, so this is the one that changes the answer.
A dowel in the track is better than nothing, but it only holds the panel shut. It does nothing about lifting.
The Two Numbers to Compare on a Quote
A patio door is mostly glass, so the glass is where nearly all the performance and nearly all the price difference sits. Every brochure says energy efficient. Ask for these two instead, both printed on the NFRC label:
- U-factor. How fast heat escapes through the whole unit. Lower is better. This is the winter number.
- Solar heat gain coefficient, SHGC. How much of the sun’s heat comes through. Lower means less summer heat. This is the number that matters on a west or south facing wall in a St. Louis August, and it is the one nobody quotes you.
Get both for the exact unit being proposed, not the range the brand publishes, and get them from both companies quoting you. Two units that look identical in a brochure can perform very differently once you see which glass is in them.
We fit ProVia units, and ProVia’s own network rates us Platinum with a showroom. The listing sits on their site rather than ours.
Screens, Blinds and Pet Doors
Screens. The sliding screen has its own rollers and its own track, and it is the part that gets abused most, because it is light and people shove it. Ask what the screen frame is made of. An aluminum frame survives a dog; a thin roll-formed one does not.
Blinds between the glass. They sit inside the sealed unit, so nothing hangs in the way of the panel and nothing needs dusting. The trade is that they cannot be serviced without opening the unit, so if the mechanism fails you are replacing glass.
Pet doors. Two routes. A panel insert stands in the track beside the door and narrows the opening by its own width, typically 10 to 12 inches, which on a door that was already tight is worth measuring first. The other route is a flap in the panel itself. That means going through an insulated glass unit, so it is a factory job on a made to order door.
Measuring the Opening Before You Call Anyone
Four readings, and they take five minutes. I take the same four on every patio door I look at.
- Width in three places, high, middle and low. The narrowest reading is the one that counts.
- Height at the left, the center and the right. Shortest of the three counts.
- Depth through the wall. Measure from the inside trim right through to the outside cladding.
- Both diagonals. If they differ, the opening has moved and the new unit has to be shimmed to suit it.
Then note which side the moving panel is on as you look at it from inside, and whether the floor outside is a deck, a patio slab or bare ground. On the newer subdivisions out toward St. Charles and O’Fallon it is nearly always a deck, and a deck built level with the threshold is the one that needs the most care. That detail decides how the sill gets flashed, and flashing is what keeps water out of the wall.
When a Slider Is the Wrong Call
- You move big things through it. Furniture, a wheelbarrow, a kayak. Half an opening will annoy you every time.
- The door is your main entrance. Sliders are back-of-house doors. An entry door does a different job.
- The existing frame is sound and only the rollers have gone. You do not need a door company for that. Get the rollers changed.
- The sill underneath has rotted. A new door will not fix that, and setting one on soft framing wastes it. That is a carpentry question, not a door question, and it gets dealt with first.
- It is a commercial building. The units we fit are built for houses.
One limit on all of it. Measurements tell you what will fit. What the job costs depends on what is behind the trim, and no web page can see that. Finished work is on our photo gallery.
Common Questions
Getting a Quote You Can Compare
Walk the room with the opening table, take the four measurements, and ask both companies for the U-factor and the solar heat gain of the exact unit. With those in hand two prices become comparable instead of two numbers.
Our sliding patio door replacement page sets out the ranges we carry, and the workmanship carries a 10 year guarantee. The in-home estimate is free and carries no obligation, and the number is 314-277-5952.
