PVC window installation: the steps and how to check the work

The installation steps

1. Remove the old window and prepare the opening: cleaning, levelling.
2. Set the frame level and plumb and fix it with anchors.
3. Fill the gap with mounting foam.
4. Water- and vapour-proof the joint: vapour-permeable tape outside, vapour barrier tape inside.
5. Fit the sill and the drip edge.
6. Hang the sashes, adjust the hardware and finish the reveals.

Why the joint matters so much

Foam absorbs moisture and degrades in sunlight, so it is protected with tape on both sides. If the sealing is done wrongly, the window develops draughts, frozen reveals and condensation around the perimeter.

Handover checklist

• the frame is straight and the sashes do not open or close by themselves
• the sashes press tight all around and the seal is not twisted
• handles and hardware move smoothly, without catching
• no scratches or chips on the glass or the profile
• foam is not sticking out or visible and the joints are finished
• the drip edge and sill are fixed with no gaps

What you should keep

The contract listing the work and warranty obligations, the handover act and the window care instructions. Keep them: you will need them if warranty questions come up.

Typical installation mistakes

• the frame is held by foam only, without anchors
• no vapour or waterproofing tapes around the perimeter
• the frame is not set level and plumb
• foam is left in the light unprotected
• the gap between the sill and the frame is not filled

How to prepare in advance

1. Clear the sill and the space by the window.
2. Decide on the colour, reveals and sill before the measurement.
3. Make sure the opening is accessible and furniture is moved.
4. Agree who will be present on installation day.