Comment installer des fenêtres à guillotine simple : un guide étape par étape

Installing a new single-hung window yourself can be a rewarding project, saving you money on labor costs. It involves careful measuring, removing the old unit (if necessary), preparing the opening, setting the new window level and plumb (straight), securing it, insulating, and sealing against weather.

This guide provides step-by-step instructions for installing a typical flanged (nailing fin) single-hung window, suitable for DIYers with basic carpentry skills.

Before You Begin: Is DIY Right for You?

• Skills Needed: Basic carpentry, accurate measuring, using a level, caulking.
• La sécurité avant tout : Always wear lunettes de sécurité et gloves. Working on ladders for upper floors requires extreme caution – consider professional help for high windows.
• Cost Factor: DIY saves on labor (see installation cost factors), but mistakes can be costly. Ensure you budget for tools and materials. Professional installation guarantees proper sealing and often includes a warranty. (Compare DIY vs Pro Installation Costs).

Need a refresher? Learn ce qu'est une fenêtre à guillotine simple first.

Outils et matériaux dont vous aurez besoin

Gather everything before you start:

Outils:

• Measuring tape
• Level (2-foot or longer recommended)
• Couteau utilitaire
• Pied-de-biche
• Marteau
• Drill/driver (if using screws)
• Caulk gun
• Putty knife (for removing old caulk/paint)
• Lunettes de sécurité
• Gants de travail
• Drop cloths

Matériels:

• New single-hung window (correct size for the rough opening)
• Cales (wood or composite)
• Galvanized roofing nails (approx. 1 1/2″ – 2″) OR exterior-grade screws (long enough to penetrate framing by 1″)
• Window & Door spray foam insulation (low-expansion)
• Exterior-grade sealant/caulk (silicone or polyurethane)
• Self-adhering flashing tape (sill flashing, jamb flashing – minimum 4″ width)
• Optional: Backer rod (for large gaps before caulking)

Step 1: Prepare the Window Opening

Accurate preparation is key for a successful installation.

1. Measure the Rough Opening:
   • Measure the width at the top, middle, and bottom. Use the le plus petit mesures.
   • Measure the height on the left, middle, and right. Use the le plus petit mesures.
   • The rough opening should typically be about 1/2 inch wider and taller than the actual window frame size (excluding the nailing fin) to allow for shimming and squaring. (Check tailles de fenêtres standard for reference).
2. Remove the Old Window (If Applicable):
   • (For detailed steps, see our guide on removing old windows).
   • Cut caulk/paint lines around interior and exterior trim with a utility knife.
   • Carefully pry off interior and exterior trim.
   • Remove any screws or nails securing the old window frame.
   • Lift or pry the old window unit out of the opening.
3. Clean and Inspect the Opening:
   • Remove old caulk, insulation, nails, and debris from the sill (bottom) and jambs (sides).
   • Check the wood framing (sill, studs, header) for any rot or damage. Make necessary repairs avant proceeding. A solid, square opening is crucial.
4. Apply Sill Flashing:
   • Cut a piece of self-adhering flashing tape several inches longer than the width of the sill.
   • Apply it firmly to the rough sill, extending up the jambs about 6 inches on each side and slightly over the exterior edge. This creates a waterproof pan.

Step 2: Set the New Window

Handle the new window carefully to avoid damage.

1. Dry Fit the Window:
   • Carefully lift the new window and place it into the opening from the exterior, resting it on the sill.
   • Center it roughly side-to-side. Check if it fits without being forced. There should be a small, even gap around the sides and top for shimming. Remove the window.
2. Apply Caulk (Optional but Recommended):
   • Run a continuous bead of exterior caulk on the wall sheathing where the à l'intérieur edge of the nailing fin will sit. This provides an extra layer of sealing.
3. Install the Window:
   • Carefully set the window back into the opening, pressing the nailing fin firmly against the wall sheathing (and into the caulk bead, if applied).
   • Have a helper hold the window steady if needed.

Step 3: Level, Plumb, and Shim

This step ensures the window operates correctly.

1. Shim the Sill:
   • Place pairs of shims under the window sill from the outside, near the corners and potentially in the middle for wider windows.
   • Use your level on the rebord de fenêtre (not the rough opening sill). Adjust shims until the window is perfectly level side-to-side.
2. Temporarily Fasten:
   • Drive one nail or screw through a hole in the nailing fin near one top corner, but don’t drive it all the way in.
3. Plumb and Shim the Jambs:
   • Place your level vertically against one of the side jambs (inside the house is easiest).
   • Insert pairs of shims (one from inside, one from outside) behind the nailing fin near the top, middle, and bottom of that jamb. Adjust shims until the jamb is perfectly sonder (straight up and down).
   • Temporarily fasten that side jamb near the top corner.
   • Repeat the plumbing and shimming process for the other side jamb.
4. Check for Square and Operation:
   • Measure diagonally from corner to corner inside the window frame. The measurements should be equal (or very close) if the window is square.
   • Carefully open and close the bottom sash. It should move smoothly without binding. If it sticks, re-check level, plumb, and square, adjusting shims as needed. Do not force tight shims, as this can bow the frame.

Step 4: Secure the Window

Once level, plumb, square, and operating smoothly, permanently fasten the window.

1. Fasten the Nailing Fin:
   • Drive nails or screws through the pre-drilled holes in the nailing fin around the entire perimeter. Follow manufacturer spacing recommendations (usually every 8-12 inches and near corners).
   • Ensure fasteners are snug but do not overtighten, which can distort the frame. The fin should lie flat against the sheathing.

Step 5: Flash and Seal the Exterior

Proper flashing prevents water intrusion.

1. Apply Jamb Flashing:
   • Apply self-adhering flashing tape over the side nailing fins, extending from about 6 inches below the sill flashing up to about 6 inches above the top edge of the window. Press firmly.
2. Apply Head Flashing:
   • Apply flashing tape over the top nailing fin, ensuring it overlaps the side (jamb) flashing on both ends by several inches. This directs water away from the window.
   • Important: Do NOT tape over the bottom nailing fin if your window has one. This allows any trapped water to escape.

Step 6: Insulate and Seal the Interior

Fill the gaps to prevent drafts. (Proper insulation is key for window energy efficiency).

1. Apply Low-Expansion Foam:
   • From inside the house, carefully spray the low-expansion foam insulation into the gap between the window frame and the rough opening studs/framing.
   • Apply a small bead; it will expand. Work from bottom to top on the sides, then across the top. Avoid overfilling, as excessive expansion can bow the window frame and hinder operation. Let the foam cure according to the manufacturer’s instructions (usually a few hours).
   • Once cured, you can trim any excess foam that protrudes beyond the wall surface with a utility knife.
2. Apply Interior Sealant (Optional but Recommended):
   • For an extra layer of air sealing, you can apply a bead of paintable interior caulk or sealant where the window frame meets the interior wall surface or trim.

Step 7: Reinstall Trim

Finish the interior and exterior appearance.

1. Exterior Trim: Reinstall the exterior trim pieces you removed earlier, or install new trim. Ensure it fits snugly against the window frame and the siding/wall surface. Fasten securely with exterior-grade nails or screws.
2. Interior Trim/Casing: Reinstall the interior window casing or trim around the window frame.
3. Caulk Trim: Apply a bead of exterior-grade caulk where the exterior trim meets the siding and where the trim meets the window frame. Apply interior paintable caulk where the interior trim meets the wall and window frame. This seals gaps against drafts and moisture and provides a clean finish.

Step 8: Final Checks and Cleanup

Ensure everything is working correctly.

1. Test Operation Again: Open and close the bottom sash multiple times. Check that it slides smoothly and locks securely.
2. Clean the Window: Remove any labels, fingerprints, or installation debris from the window glass and frame using an appropriate glass cleaner.
3. Clean the Work Area: Remove drop cloths, sweep up debris, and dispose of the old window and waste materials properly.

Common Installation Mistakes to Avoid

• Inaccurate Measuring: Leads to windows that don’t fit or have excessive gaps. Measure twice, order once.
• Not Leveling/Plumbing: Causes operational problems (sticking sash) and potential leaks. Use your level diligently.
• Over-Shimming/Forcing: Bowing the frame makes the window difficult or impossible to operate. Shims should be snug, not forced.
• Over-Tightening Fasteners: Distorts the frame. Fasteners should be snug, holding the fin flat.
• Improper Flashing: Skipping flashing or applying it incorrectly (wrong order, no overlaps) is a primary cause of leaks. Follow the sill -> jambs -> head sequence.
• Using High-Expansion Foam: Can bow the window frame. Always use low-expansion foam specifically for windows and doors.
• Skipping Caulk/Sealant: Leaves gaps for air and water infiltration. Seal thoroughly inside and out.

If you encounter issues like a window not staying up after installation, it might indicate a problem with the balance system or improper shimming – see our guide on window repairs.

Maintaining Your New Single-Hung Window

Regular care keeps your window looking and performing its best. See our full guide on how to clean and maintain windows. Key tips include:

• Nettoyage régulier : Clean glass and frames periodically.
• Track Cleaning: Keep the bottom track clear of dirt and debris for smooth operation.
• Check Seals: Inspect caulk and weatherstripping annually and repair/replace as needed.
• Inspect Operation: Ensure the sash continues to move freely and lock securely.

Conclusion: A Job Well Done

Installing a single-hung window yourself requires careful planning, precise measurement, and attention to detail, especially regarding leveling, plumbing, and weather sealing. By following these steps, using the right materials, and avoiding common pitfalls, you can successfully install your new window, enhancing your home’s appearance and energy efficiency while saving on installation costs.

However, if you feel unsure at any stage, especially regarding structural integrity, flashing techniques, or working at heights, don’t hesitate to call a professional window installer. Their expertise ensures a proper, warrantied installation for lasting performance. Get quotes to understand professional installation costs.