How to Add a Window to a House

Open window looking out onto the sea

Adding a window to one of the exterior walls of your home can make your house feel brighter and more spacious. Working with exterior walls is something that must be done with great care, however. If the installation is not done correctly then it could lead to issues with damp and draughts, at best. At worst it could lead to serious structural problems.

If you are an experienced builder, it is possible to do the job by yourself. It is not a job that is suitable for the average DIY enthusiast, however. To avoid potentially expensive and time consuming repairs, we strongly recommend that you hire a professional to do the job for you.

How Do You Install Exterior Windows?

If you are committed to the idea of installing a new window yourself (or just interested in the process involved), then study these tips first.

This is one scenario when the mantra “measure once, cut twice” really does apply!

You will need:

  • Drywall
  • The new window (and frame)
  • Drill
  • Hammer
  • Reciprocating saw
  • Shims
  • Chop saw
  • A stud finder
  • Nails
  • Level

Before you begin:

The first step is to find the right location to install the window. This may not be the “perfect” location in your mind. You should make sure that the area is free from water pipes and electrical wiring, and is located between the studs in the wall. Use a stud finder to determine the location of the studs. If you cannot find a suitable place to install the window because there are wires and pipes covering too many areas, call a professional and get their advice before starting work.

Preparing the Area

If your home has vinyl siding, remove it – carefully. The siding will be reinstalled once you have installed the area. Mark the location of the window on the exterior wall, using the dimensions given by the window manufacturer. Measure these carefully and use a level to make sure that the window is aligned properly.

Make a Frame

Make a rectangular frame with a double header. There should be a pair of 2x6s at the top, that are wide enough to give the window clearance. The joints should be connected with wood glue and three inch screws.

Cut the Wall

Cut the wall using a reciprocating saw, taking (great) care to make sure that the opening is no bigger than the frame. Take out the crown and baseboard, and cut the sheetrock at the same time.

Install the Frame

Put the frame into the window and screw it into the studs. Check to make sure the window is level, and use shims if required. Add screws and re-check the level periodically until the window is secure.

Once the window is in place, replace the sheetrock and patch the wall up. Replace the sidings, add the window trim, weather strips and caulking.

A Few Tips

Take care to ensure that the window opening is exactly the right size, and use insulation to prevent draughts. Add a generous amount of weatherproof stripping to the internal frame to prevent water ingress.

Installing a new window is a big job, and we’d like to re-iterate that it is not a standard DIY task. If you are unsure about any of the above steps, call in an expert to do the job for you – it will almost certainly save you time and money.

Looking for new windows for your home? Browse our sliding sash or casement windows or find out about our handmade bespoke windows.