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Sliding vs. French Patio Doors for a Canadian Winter: Sealing, Wind, Space, Screens, Security and Price, Decided by the Deck They Open Onto
Windows & Doors
Sliding or French: One Seals Better, One Never Swings Into the Barbecue, and the Deck Usually Decides
A sliding patio door and a pair of French doors fill the same 6-ft hole and behave nothing alike. One slides past itself on rollers behind a brush seal and leaves the deck free. The other closes against a gasket like a front door, seals tighter, and needs 3 ft of clear floor on one side or the other. Here is each one in an Ontario winter, and the question that settles it.
The numbers
$3,2006-ft vinyl slider, installed
$4,2006-ft French doors, vinyl or steel, installed
3 ftof swing clearance a French door needs
2 to 3xthe air leakage of a slider vs. a swing door, typical ratings
Sliding
One panel fixed, one on rollers, pile weatherstrip between them and a hook lock at the meeting stile. The screen is outside on its own track. It takes no floor space, it cannot be blown shut or open, furniture can sit beside it, and a good one with a foot bolt is as secure as any door. The price of all that is the seal: a brush cannot press hard against something that has to slide past it, so a slider leaks more air than any other door in the house, and the meeting rail is a cold line down the middle. The rollers wear and the track fills with grit; a slider that is hard to move is a $120 roller job, not a new door.
French (or garden)
Two panels hinged at the outside, meeting in the middle, one or both swinging. Each closes against a compression gasket on three sides and a sweep at the sill, like a front door, so the air leakage is a fraction of a slider’s and the glass can be anything a door can carry. The price: 3 ft of clear floor inside (in-swing) or deck outside (out-swing); a screen that is a separate retractable or a hinged panel, never as good as the slider’s; the astragal and the flush bolts on the inactive panel that have to be set every time; and wind. An out-swing French door on a lakeside deck in a west wind is a door that gets caught, and an in-swing one is a door that gets blown open if the latch is weak.
Side by side
| Measure | Sliding | French |
|---|---|---|
| Installed, 6 ft, vinyl | $3,200 | $4,200 |
| Air seal | Brush; the leakiest door | Compression; tight |
| Floor or deck space | None | 3 ft clear one side |
| Screen | Built in, outside track | Retractable or hinged add-on |
| Wind | Does not care | Catches it, both ways |
| Security | Good with a foot bolt; weak with the stock hook | Good with a multipoint; weak with flush bolts alone |
| Glass area | Most; thin stiles | Less; door stiles and the astragal |
| Maintenance | Rollers, track | Hinges, flush bolts, weatherstrip on two doors |
| Looks | Modern or plain | Traditional, a door that looks like a door |
Three decks where the answer is obvious
- A small deck with the table and the barbecue right outside. Slider. A French door opens into the barbecue or the chairs, and nobody moves them.
- A covered porch, in-swing, on a traditional house. French. The seal, the look, and the porch keeps the wind off.
- A lakeside deck facing the prevailing wind. Slider, or a French door with a proper multipoint lock and a closer, and even then the slider is the one that will still be hanging straight in ten years.
The third option: a three-panel slider with a wide centre fixed panel and sliders at both ends, 9 or 12 ft, gives the glass of a wall, the seal of a slider on two narrow panels, and no swing. It is what I put on walkout basements facing the lake.
Where homeowners go wrong
- French doors for the look, with the wind off the lake. Then a door closer, then a new latch, then a slider.
- A slider with the stock hook lock on a dark side of the house. Foot bolt and a security bar, $350, the day it goes in. Locks.
- In-swing French doors in a small room. The 3 ft of floor is the room.
- Either one on a sill set on shims. The floor under it is the next job. The threshold.
Questions people ask
Are French doors colder than sliding doors?
No; the reverse. A swing door seals on compression and leaks less air. The glass is the same. A slider is colder at the meeting rail and around the brush seals.
Are sliding doors more secure than French doors?
Equal, with the right hardware; weak, both, with the stock hardware. A foot bolt on a slider and a multipoint on a French door put them both ahead of most front doors.
Which costs more, French or sliding?
French, by about $1,000 for 6 ft in vinyl, more in fibreglass. Two doors, two sets of hardware, two sets of weatherstrip.
Price both
The door calculator has sliders, French doors and the three-panel version, with the floor, the wall and the options.
Sources and further reading
- Keeping the Heat In: Natural Resources Canada. The free guide to windows, doors, air sealing and insulation written for Canadian houses.
- JELD-WEN Canada: windows and exterior doors; the rough opening sheets and warranty documents are on the site.
