Install a sliding patio door: fitting and weatherproofing
A sliding patio door has become the signature feature of a contemporary living room: it opens the living space onto the terrace, floods the room with light and defines the entire rear facade. But a 4 m wide door unit also means 200 to 350 kg of joinery resting on a near-flush threshold, with as many weatherproofing joints as there are frame sections — making it the most demanding joinery task in a self-build. Choosing the right type (standard overlap, pocket/galandage, lift-and-slide), sizing the lintel and threshold, managing perimeter weatherproofing and meeting the wheelchair-accessible step-height requirement in new construction: this guide covers the entire chain, from specification to final installation, for a door that lasts 30 years without leaks.
Three families of sliding doors: which one to choose?
Before even discussing materials or glazing, you need to decide on the mechanism type. Three families co-exist on the French market, and the choice determines all the opening sizing that follows.
1. The standard overlap sliding door
The default for new builds. Two to four leaves that slide behind each other on parallel tracks. In practice, you never have more than half the opening clear (one leaf overlaps the other). Robust mechanism, controlled cost, proven weatherproofing — the default choice for 80% of projects.
- Pros: price, reliability, simple installation, wide catalogue of sizes
- Cons: only 50% of the opening is ever clear
- Installed price: €1,500–3,500 for 240 cm × 215 cm in aluminium
2. The pocket sliding door (galandage)
The leaves disappear into a cavity built into the side walls (the “galandage” pocket). When fully open, the door gives a 100% clear passage between inside and outside — ideal for merging living room and terrace in summer. However, the wall thickness must be sufficient to absorb the stacked leaves (24–30 cm minimum) and the masonry must be designed for it from the outset (you cannot create a pocket in renovation without demolishing the partition).
- Pros: full opening, “frameless” aesthetic, wow factor
- Cons: high price, water weatherproofing more complex, thick wall mandatory
- Installed price: €4,500–9,000 for 360 cm × 215 cm in aluminium
3. The lift-and-slide door (Hebe-Schiebe)
A premium German mechanism. The handle actuates a system that lifts the leaf 5 mm before it slides on its tracks — enabling compression seals instead of conventional brush seals. The result: superior air and water tightness, excellent thermal performance (Uw 0.8–1.1) and the ability to move leaves up to 400 kg.
- Pros: large dimensions possible (leaves up to 3 m tall), perfect weatherproofing, durability
- Cons: very high price, single-hand operation impossible on large models
- Installed price: €6,000–15,000 depending on size
Tip — For a standard RE2020 house, the thermal-break aluminium overlap sliding door is unbeatable value for money. Reserve the pocket door for a project where a fully clear opening genuinely changes how the space is used (covered terrace, summer kitchen) and the lift-and-slide for XXL openings (> 4 m wide or > 2.5 m tall) where weight rules out the standard slider.
Materials and profiles: aluminium, uPVC or composite
On a sliding patio door, the frame material determines the profile slenderness, thermal performance and budget.
| Material | Profile width | Uw (indicative) | Relative price | Service life |
|---|---|---|---|---|
| uPVC | 100–130 mm | 1.4–1.6 | × 1 (reference) | 30–40 years |
| Aluminium thermal break | 65–90 mm | 1.3–1.5 | × 1.5 | 50+ years |
| Composite alu/timber | 80–100 mm | 1.1–1.3 | × 2.5 | 50+ years |
| Hardwood | 90–120 mm | 1.2–1.4 | × 2 | 30 years (maintenance) |
Thermal-break aluminium (RPT) = the reference for new sliding doors. Slim profiles (the frame almost disappears visually), large sizes possible, zero maintenance, polyamide thermal break insulator that cuts the cold bridge between inside and outside. To avoid: aluminium without a thermal break (old or budget-import profile) that condenses in winter and carries a Uw > 2.5.
uPVC = budget solution; bulkier profiles (less refined aesthetics at large sizes), good baseline thermal performance but limited to openings < 3.60 m wide.
Composite aluminium-outside / timber-inside = technical luxury: durable aluminium on the weather side, warm timber on the room side. Very good thermal performance. High price, especially at large widths.
Dimensions, lintel and load transfer
A sliding patio door is a large-span opening: it interrupts the masonry over 2.4 to 5 m and requires a properly sized lintel.
Standard market sizes
| Opening width | Opening height | Leaves | Use |
|---|---|---|---|
| 180 × 215 cm | 2 leaves | Small kitchen or study door | |
| 240 × 215 cm | 2 leaves | Standard living room | |
| 300 × 215 cm | 2 or 3 leaves | Generous living room | |
| 360 × 215 cm | 3 leaves | Large open-plan room | |
| 480 × 215 cm | 4 leaves | Panoramic living space | |
| 240 × 240 cm | 2 leaves | Extra ceiling height |
Beyond 480 cm wide or 240 cm tall, switch to a lift-and-slide or assemble two units on a mullion.
Lintel sizing
The lintel carries the floor slab and roof load above the opening. The wider the door, the deeper and heavier the reinforcement needs to be. Three options:
- Cast-in-place reinforced concrete lintel — the standard. Depth ≈ opening width / 10, minimum 20 cm. Reinforcement: 4 × HA12 bars + HA6 links at 150 mm centres. For a 360 cm opening: 36 cm deep lintel, HA14 bars.
- Pre-stressed precast concrete lintel — time-saving, supplied to size. Choose the series based on span and load (Rector, KP1 catalogue).
- Steel IPE beam or glulam on timber frame — alternative solution, welded or nailed connections as appropriate.
Warning — For any opening over 300 cm wide, have the lintel sizing validated by a structural engineer or your frame contractor. A door that sticks six months after installation means leaves dragging against the frame: a sure sign the lintel has deflected due to undersizing. See our dedicated guide on opening a load-bearing wall for the full method.
The threshold: flush-fitted or surface-mounted
This is the most technical aspect of a sliding patio door.
- Flush-fitted threshold (with thermal break) — the RE2020 standard and wheelchair accessibility requirement. The track is cast into the concrete slab, with inside and outside surfaces at the same level, step height ≤ 20 mm (French accessibility decree, 20 April 2017). Watertight when correctly sealed with expansion tape and EPDM flashing.
- Surface-mounted threshold — the track sits on top of the slab, with a 60–80 mm step up to the interior. Easier to seal, but not wheelchair-accessible in new residential builds.
In new construction, plan the flush threshold when pouring the slab: the recess must be formed in the shuttering (10–15 cm deep over the full frame width + 30 mm clearance). Retrofitting a flush threshold into a finished slab means cutting, patching the waterproofing and extra lead time.
Visual comparison of the 3 types
Tools and materials for installation
| Item | Purpose | Qty |
|---|---|---|
| 2 m spirit level + slope level | Levelling the threshold | 1 |
| uPVC or hardwood packers | Packing under frame | 8–12 per door |
| Impact driver + aluminium/masonry bits | Fixing brackets | 1 |
| Galvanised or stainless steel fixing brackets | Anchoring into masonry | 8–14 per door depending on width |
| Expansion sealing tape TP600 (15 × 4 mm) | Air seal under frame and sides | 2 × door perimeter |
| Self-adhesive EPDM flashing tape | External water seal | door perimeter |
| Low-expansion PU foam | Interior draught-filling | 2–4 cartridges |
| SP1 facade sealant (neutral silicone) | Final external bead | 2–3 cartridges |
| Double glazing suction cups | Handling glazed leaves | 2 pairs |
| Ratchet straps | Handling the frame | 2 |
| Plumb bob / laser plumb | Frame plumb | 1 |
At least 3 (ideally 4) people are required for openings over 300 cm wide. The aluminium frame alone on a 360 × 215 cm door weighs 60–80 kg; each glazed leaf adds 50–90 kg. Suction cups are rated for no more than 30–40 kg per pair — check the class of your cups (P3 minimum).
Step-by-step installation method
Installing a sliding patio door in a new build takes one day with 3 people, provided the masonry was designed from the outset to receive it. Here is the sequence to follow in order.
1. Check the opening
- Width: rough opening = frame width + 20 mm (10 mm each side)
- Height: rough opening = frame height + 30 mm
- Plumb: check that vertical reveals do not deviate by more than 5 mm over the height
- Level: sill / threshold recess at the correct datum, perfectly level to within 2 mm over 2 m
- Condition: no frost damage, no mould, chainwork mortar fully cured (> 28 days)
If the opening is too wide, pack with mortar before installation (and wait 7 days). If the plumb is off, do not install until it is corrected: a frame fitted in an out-of-plumb opening will have leaves dragging for its entire life.
2. Prepare the threshold (flush-fitted)
- Clean out the recess, remove dust and debris
- Pour a bedding mortar bed (M10 fluid mix, e.g. Lankoflo) 10–20 mm thick into the recess
- Lay a strip of bitumen felt DPC or flexible SBS membrane around the full perimeter of the threshold recess as a capillary break
- The track will be levelled precisely on this bed after packing
3. Offer up the frame
With 3 people: offer up the complete frame (delivered as an assembled unit for standard sizes, or as a site-assembled kit for very large sizes). Lower it into the opening without tightening at first. Check with level and laser:
- Level threshold (spirit level along the full length)
- Plumb vertical posts (plumb bob or 90° laser)
- Square (measure both diagonals of the frame: they must match within 2 mm)
4. Packing and fixing
- Pack under the threshold with uPVC packers every 30–40 cm so the track is perfectly level and the frame is not in compression on its own base
- Pack laterally with calibrated packers between vertical posts and reveals
- Fix the brackets into the masonry: every 60–70 cm, with expansion anchors or chemical anchors depending on the substrate
- Screw the brackets to the frame using the screws provided by the manufacturer (pre-drilled holes on standard profiles)
Best practice — Never use PU foam to pack a sliding door frame. Foam expands as it cures and can distort the frame along its length, causing leaves to drag. The frame must be mechanically fixed by brackets; PU foam is only used for draught-filling (step 6), never for packing.
5. Air sealing (expansion tape)
Once the frame is definitively fixed:
- Expansion sealing tape 15/4 mm applied in a continuous bead around the full perimeter of the external face of the frame (under the threshold, along the posts, across the top)
- Allow the tape to expand for 24 hours minimum: it reaches its final dimension and conforms to any irregularities in the reveal
6. Interior PU foam
- Low-expansion polyurethane foam (e.g. Soudal Soudafoam Low Expansion) injected into the gap between frame and reveal on the interior side
- Not at the base on the threshold side: foam lifts the slim tracks
- Allow 4 hours to cure, then trim flush neatly with a stanley knife
7. External water seal
- Self-adhesive EPDM flashing tape applied in a U shape over the frame/concrete sill junction, turned up 50 mm on the side posts
- SP1 facade sealant bead (neutral silicone, e.g. Sika 11FC) applied continuously around the full external perimeter in a solid bead, neatly finished at corners
- No acrylic sealant: it does not hold against water or UV and will peel away within 18–24 months
8. Fitting the leaves and adjusting
- Insert the leaves onto the tracks from the inside, starting with the back (fixed) leaf
- Adjust the rollers via the height adjustment screws accessible at the bottom of each leaf (usually 5 mm Allen key)
- Check that each leaf glides without dragging over its full travel
- Check that the brush seals press uniformly against adjacent glazing units
- Adjust the multi-point lock: the handle should turn without stiffness
9. Interior finishes
- Decorative acrylic bead between frame and interior plaster (paintable)
- Fit the reveal liners (uPVC, MDF or plaster) if specified
- Interior window board if the door does not extend to floor level (rare on sliding patio doors)
Weatherproofing at the critical point: the threshold
Water infiltrates through 9 out of 10 sliding doors at the threshold. It is the only point that combines direct run-off, a low step height and pedestrian traffic. Four successive layers must be respected:
- External drainage fall on the concrete slab or terrace, directed outwards at minimum 1.5% over 80 cm
- Self-adhesive EPDM flashing tape under the frame, overlapping 50 mm each side and turned up 50 mm on the posts
- Expansion air seal tape on the top edge of the threshold to block air infiltration
- SP1 facade sealant bead continuously around the exterior perimeter of the frame after installation
On a covered terrace or patio, add a longitudinal drainage channel in front of the door, connected to the rainwater downpipe. Without a channel, the slightest driving rain seeps under the frame and saturates the slab insulation.
Thermal performance and RE2020 compliance
A sliding patio door is by nature the thermal weak point of an insulated wall: Uw 1.3 versus a wall Ug of 0.15 — eight times more heat loss per m². Hence the importance of carefully managing the glazed-to-floor-area ratio and specifying the right glazing.
| Configuration | Indicative Uw | RE2020 status |
|---|---|---|
| Alu thermal break + standard double 4/16/4 | 1.5 | Borderline compliant |
| Alu thermal break + low-E argon double 4/16/4 | 1.3 | Compliant |
| Alu thermal break + triple 4/12/4/12/4 | 0.9 | Passive house |
| Composite alu/timber + triple low-E | 0.8 | Passive house |
Recommended choice for a standard new build: thermal-break aluminium frame + low-E argon-filled double glazing (Ug 1.1, Uw 1.3). For a south-facing orientation without overhangs or blinds, specify solar-control glazing (g ≤ 0.4) to limit summer overheating — or plan for external blinds or an adjustable sun louvre.
Full details on glazing: see our guide choosing single, double, triple or low-E glazing.
Common mistakes to avoid
Warning — The 10 mistakes that turn a new door into a defect claim:
- Undersized lintel → deflection, leaves dragging, cracks above the opening
- Out-of-plumb reveal not corrected before installation → twisted frame, uneven seals
- Packing with PU foam instead of mechanical packers → threshold distortion
- Missing expansion air seal tape → permanent draughts, condensation on the frame
- Acrylic sealant instead of SP1 → external delamination within 18 months
- No EPDM flashing tape under the threshold → direct water infiltration into the slab
- Missing or reversed drainage fall → puddle in front of the door, infiltration
- Step height > 20 mm in new residential build → non-compliant, rejected at handover
- Installing in rain → seals won’t bond, mortar washes out
- Rollers not adjusted → stiff leaves, brush seals worn out within 2 years
Decision tree: which door to choose?
2 leaves, low-E argon] B -->|No| F[Alu thermal break slider
2 leaves, low-E argon] C -->|Yes wall >= 24 cm| G[Pocket sliding door
alu thermal break, low-E argon] C -->|No / thin wall| H[Alu thermal break slider
2 or 3 leaves] D -->|Yes| I[Lift-and-slide door
alu or composite, double or triple] D -->|No| J[Alu thermal break slider
3 or 4 leaves] style A fill:#0F4C81,stroke:#0F4C81,color:#fff style B fill:#0F4C81,stroke:#0F4C81,color:#fff style C fill:#0F4C81,stroke:#0F4C81,color:#fff style D fill:#0F4C81,stroke:#0F4C81,color:#fff style E fill:#56C6A9,stroke:#56C6A9,color:#fff style F fill:#56C6A9,stroke:#56C6A9,color:#fff style G fill:#F58220,stroke:#F58220,color:#fff style H fill:#56C6A9,stroke:#56C6A9,color:#fff style I fill:#F58220,stroke:#F58220,color:#fff style J fill:#56C6A9,stroke:#56C6A9,color:#fff
Cost of an installed sliding patio door (2026)
Self-installation (DIY)
| Item | Indicative price |
|---|---|
| Alu thermal break door 240 × 215 cm (2 leaves, low-E argon) | €1,200–1,800 |
| Alu thermal break door 360 × 215 cm (3 leaves, low-E argon) | €2,200–3,500 |
| Pocket sliding door alu 360 × 215 cm | €4,500–7,000 |
| Lift-and-slide door alu 480 × 240 cm | €8,000–13,000 |
| Brackets + packers + fixings | €30–60 |
| Expansion tape + EPDM + SP1 sealant | €80–150 |
| Low-expansion PU foam | €25–40 |
| Total DIY supply cost | per model + €150–250 accessories |
Professional installation
Labour only (excluding supply): €400–900 per unit depending on size and access, 10% VAT for renovation, 20% for new build.
| Configuration | Installed price (new build) |
|---|---|
| 240 × 215 cm alu thermal break low-E argon | €2,500–3,500 |
| 360 × 215 cm alu thermal break low-E argon | €3,500–5,000 |
| Pocket sliding door 360 × 215 cm | €6,500–10,000 |
| Lift-and-slide 480 × 240 cm | €10,000–18,000 |
DIY saving: €800 to €2,500 per unit depending on size, but the self-builder forgoes the joinery contractor’s ten-year structural warranty. On a correctly installed door, this risk is low; on a defective installation (failed weatherproofing), it becomes significant. Factor this into your decision.
Standards and resources
- DTU 36.5 — Installation of windows and external doors (the French standard for windows and external door installation — main reference)
- DTU 39 P5 — Glazing and mirror work
- NF EN 14351-1 — Performance and CE marking of windows and pedestrian doors
- NF EN 12207, 12208, 12210 — AEV classification (air permeability, water tightness, wind resistance)
- French accessibility decree, 20 April 2017 — Wheelchair accessibility (step ≤ 20 mm)
- RE2020 (decree 2021-1004) — Energy performance of new buildings
- CSTB — DTU reference library for official texts
- Schuco — aluminium sliding doors
- Technal — patio door range
- K-Line — thermal break aluminium sliders
- Sika — SP1 facade sealant
- Tremco illbruck — expansion sealing tape TP600
Checklist before ordering your door
Checklist: sliding patio door installation
- Door type chosen: standard overlap, pocket or lift-and-slide
- Opening dimensions taken: width + 20 mm, height + 30 mm clearance
- Reveal plumb checked over full height (< 5 mm deviation)
- Lintel sized (structural engineer check for > 300 cm wide)
- Threshold recess formed in slab pour (flush-fit, RE2020 compliant)
- External drainage fall planned (1.5% outward over 80 cm)
- Drainage channel in front of door on covered terrace
- Frame material and profile chosen: thermal-break alu, uPVC or composite
- Glazing specified: low-E argon double (Uw ≤ 1.3) for standard RE2020
- Solar-control glazing specified (g ≤ 0.4) for south-facing without shading
- Fixing brackets, uPVC packers, expansion tape TP600 and EPDM tape ordered
- SP1 facade sealant (not acrylic) specified for exterior
- Low-expansion PU foam (not standard) for draught-filling
- Minimum 3 people available for handling
- Double suction cups class P3 and ratchet straps in stock
- Dry weather forecast for 24–48 h (no rain or strong wind on installation day)
- External blinds or sun louvre planned for south-west exposure
Further reading
- Before installation, confirm your choice of uPVC, aluminium or timber profiles and single, double or triple glazing
- For breaking through the wall, see the guide on opening a load-bearing wall — essential for renovation work
- For other joinery on the same facade: fitting a double-glazed window and fitting a front door
- For associated solar shading: installing electric roller shutters or fitting hinged shutters
- For overall envelope compliance: understanding RE2020 in self-build