Window installation: a guide for pros

What customers ask, how to win the job, and what to put on your profile.

Offering window installation

Window installation is a measure-and-flash job where the rough opening, the flashing and the shimming decide whether the window works and stays dry. Your win is measuring carefully, showing the flashing plan and proving the opening was checked before the new unit went in.

What customers ask

  • Why are my windows drafty even though they are new?
  • Will the new window fit my existing opening?
  • Will the frame rot or leak in a few years?
  • What glass package do I need for my climate?
  • Can you repair the sill if it is soft?
  • What is the warranty on the glass seal?

How to win the job

  • On the first call, ask how many windows are needed, the window type, the room each one is in, and any leaks, drafts or fogging they see, so you arrive knowing the scope.
  • Bring a sample of the frame, the glass package and the flashing tape to the visit, and show the homeowner the layers around the window.
  • Measure each opening in three places and check the sill and head for level and square, photographing the rough opening before any cut.
  • Put each opening, the glass package, the frame material, the flashing and the trim in the quote as separate lines, listed by room.
  • Explain how the sill and head are flashed and why the order of the layers matters, so the homeowner sees the water path.
  • Check the rough opening for rot on the day of the install, and show the homeowner the photos before the unit goes in.
  • Send a closeout packet with the window product, glass package, warranty papers and a photo log of the flashing at each opening.

What to put on your profile

  • Before and after photos of window installs that show the flashing, the shims and the finished trim
  • Window brands, frame materials and glass packages you install
  • Window types you install, such as double-hung, casement, sliding and picture
  • Service area and whether you handle rot repair at the sill and the trim work in-house

Follow-up that helps the customer

  • Offer a window seal and hardware check after the first year, since locks and sashes can drift as the house settles.
  • Suggest a window screen or film fitting for rooms that get strong sun after the new glass goes in.
  • Recommend a check of the exterior caulk and trim at each new opening once a year.

Licenses and permits

Window installation is commonly done by licensed general or window contractors, and changes to the opening often need a permit and inspection. Check your state and local licensing and building office requirements before you bid.

Questions

Do I need a permit to replace windows?

Often not for a like-for-like swap. Enlarging or moving an opening, or changing the structure, usually needs one. Check with the local building office before you quote.

How do I handle rot found in the sill after the old window comes out?

Stop, photograph the rot, and send a priced change order before repairing it. Do not set a new window over wood that is soft or wet.

Should I use foam or another fill in the gap?

Use the fill the window maker specifies, usually low-expansion foam or a listed insulation. Over-filled foam can bow the frame. Explain the fill and the sealant plan in the quote.

About this guide

This national guide is written and checked by infinibell. Rules and conditions differ by place, so local pros are credited on guides for the cities they serve, not on national ones.

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