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Guide to Installing Replacement Windows

Welcome to the complete guide for installing your replacement windows. Before we get to the guide, we would like to mention that this is a fairly difficult Do-It-Yourself project and may not be a good project for a novice. High estimates from contractors oftentimes make doing it yourself seem like a sure money saving venture. Installing replacement windows yourself can save a little money. If it is done incorrectly, it can cost you a lot more than you would have saved. Incorrect installation can mean gaps which will drive up heating and cooling costs, allow moisture to permeate the structure and cause damage, and any other number of things that can cost you far more down the road. In addition, a quality contractor will be licensed, bonded, and insured; which means if something does go wrong with the installation you have recourse to recover damages. You do not have this protection when doing a self-installation. If you are at all uncomfortable with the project, you will be better off locating a contractor for installation services.

There are a couple additional points to consider before doing this job yourself.

Windows purchased off-the-rack are generally new construction windows. Measurements must be taken so that your replacement windows can be ordered from the manufacturer. Some companies have responded to this growing want by expanding their replacement window lines, but many have not.

Professional window installers will oftentimes seal the exterior in aluminum cladding to help form a better seal against the elements. This requires specialized tools, knowledge, and some experience to do well and correctly. These are things that professional installers will have readily available for their work orders but may not be available to you.

This guide will cover the methods used for installation of replacement windows as well as ensuring the right fit. The methods used for replacing windows are fairly uniform all around, meaning this is basically the same method a contractor uses to install them.

Material List

  • Claw Hammer
  • Small Prybar
  • Utility Knife
  • Paint Scraper
  • Wood Chisel
  • Cordless Drill (with some strength to it)
  • Wood Shims
  • Tape Measure
  • Miter Saw
  • Screwdriver
  • Dripless Caulking Gun
  • Many tubes of elastomeric caulk
  • Exterior-Grade Wood Putty
  • Sandpaper
  • The Replacement Window

Measuring Your Windows

One of the most important parts of replacing your windows is ensuring you have the correct sizes for the frame. An incorrect measurement can leave unnecessary gaps that will permit wind, weather, and pests to find their way in to the home. It will also permit the easy flow of heat or cooling from the interior to the outdoors. When you measure your windows, it is done from the inside of the house. Do not take the window measurements from the outside.

Determining Window Width

Measure your window in three locations at the top, middle, and bottom of the window. The area you are measuring is the inside of the left jamb to the inside of the right jamb. To reiterate, ensure you are measuring from the inside of the left jamb to the inside of the right jamb. Due to the nature of construction and the house settling; you may come up with different measurements. They will hopefully either be the same, or within a 1/4th " of each other. If they are not the same, use the smallest measurement as the final. This will ensure the window will fit in the frame and you can always use wood shims to ensure the fit in wider areas. If they are greater than a 1/4th "in difference, you may need to have a full frame replacement done instead of just a replacement window installation.

Determining Window Height

Measuring for the height of the window is done in much the same way. You are measuring from inside of the window sill to the inside of the top window jamb. Take three different measurements; left, middle, right. Once again, use the smallest measurement as the final for the same reasons as stated above.

Removing the Old Window

From inside the house, look at the back of the window. For clarification purposes; realize that the sash is the movable part of the window, and the stops are the vertical strips on either side of it that prevent it from falling out of the window. The material of these may differ depending on how old the window is.

Removing the Stops

The first step to undertake is removing the stops from the window. This is where your utility knife, pry bar, screwdriver come into play. You want to be very careful as you remove the stops so that you do not damage them or the surrounding materials. A utility knife is great for breaking through old paint. Once you get a gap worked into the stop, a small pry bar can make short work of getting the rest off. Provided you did not destroy the stops from trying to get them off, set them aside to be re-used at a later time.

Removing the Sashes

Once the stops are removed, the lower sash should tilt out and be removable from the frame. The upper sash could be held in through different means though it will most likely be through a parting bead. The parting bead acts much the same for the upper portion of the sash as stops do for the lower portion. It also "parts" the upper and lower sash to allow for free and easy movement. If the sash has no parting beads, push in on the jamb liner and pull the top of the sash forward and free. After this, removing the upper sash is a simple matter of pivoting it out of the hold of the jamb liners.

Removing the Jamb Liners

If the former window frame had vinyl or aluminum jamb liners mounted to it then these will need to be removed with the pry bar. Older windows may have additional wooden stops mounted on the frame that will need to come off in the same fashion. The interior and exterior casings of the frame should be left intact.

Preparing the Frame for Installation

Now is a great opportunity to do some touch up work on the frame if it is damaged in any way. An exterior-grade wood putty can be used to patch small gaps and holes in the frame. Use sandpaper to smooth the interior of the frame over the rough areas once the putty sets. If there is extensive paint flaking and bubbles on the frame, after the sanding would also be an opportune time to apply primer and a coat of paint if needed.

Old Sash Weights

Now is the time to remove the old sash weights from the frame if they are still there. Each side jamb should have an access panel; probably screwed on, that can be removed to pull out the old weights. You can take this opportunity to check the insulating qualities behind where the weights rested and patch any holes accordingly. Once this step is done, re-attach the access panels on either side.

Insulating the Frame

Purchasing an energy efficient window isn't going to mean much if the frame around it is not insulated properly. Two types of insulation are readily used and available for this installation. The first is traditional fiberglass insulation and the second is a spray-foam. Fiberglass insulation is usually installed by contractors because it is faster and cheaper. Spray-foam insulation takes a bit more time and effort but provides a far greater R-value for the window frame. Spray-foam is available both in cans and with use in a commercial-grade sprayer. The can type will work fine for this job.

When you buy foam-spray insulation, be sure it is a low-expanding type suitable for windows and doors. If it is not, the expansion of the foam could prevent the window sash from operating smoothly.

Drill a series of three holes down in the window sill and up through the top window jamb of 3/8ths inch diameter. There should be one near the left, the center, and to the right. In each hole, insert the nozzle of the can and fill until it starts to back out of the fill hole. You may also do the sash weight housing if your model of replacement window does not require their use. Be careful not to overfill or you will end up with foam all over the interior of the house. There will be some expansion outside of the fill holes. Let the spray foam set for its curing time; typically six hours. Once that time period has passed and the foam has hardened, you can break away any spray-foam that has leaked out of the drill holes and smooth them off with sandpaper.

Preparing for Window Installation

A lip should be present on the inside of the exterior casing. Apply an elastomeric caulk to the inside of this lip (or blind stops, whichever it has) and two continuous beads along the window sill. From inside the room, set the window replacement into the bottom of the frame and tip it backwards into place. Do not slide the bottom otherwise it will weaken the caulking seal the two beads are providing. Press the window tight against the caulked lip or blind stops.

Situating the Window

A 2" screw can be driven through the upper side jamb and into the framing in front of the window, to hold the window in place. Leave enough room for the window sash to operate correctly.

Situate the window in the opening until it sits in the center through the use of wood shims. There is no need to pound them in all the way in case you need to remove one. The hang off can be cut off with a utility knife or miter saw once the window is square. These will go along the bottom sill and the sides until the window is centered and fully operational.

Close and open the window a few times including securing the window latch. All operations should perform smooth and uninhibited. Once they do, you know the window is set in square and evenly. As a further check, measure the window diagonally from corner to corner. The measurements should be the same.

Once these factors have been satisfied; it is time to screw the window into place. Shims can be slipped behind the pre-drilled screw holes to screw through into the frame to ensure the window does not bow from the pressure.

Finishing Up

On the outside, you want to measure any gaps between the window frame and casing. Anything wider than a 1/4" will need to have a foam backer rod stuck into it to ensure the seal. Anything less than1/4" can be filled with elastomeric caulk. Gaps on the interior can be touched up with minimally expanding foam. After touch ups, any remaining window stops can be installed or reinstalled. The window is then ready to be primed, painted, or stained if it is of the wood variety.

This guide is meant to give you a walk-through of the job of installing replacement windows. As you can see, there is a fair bit to it to ensure it is done correctly. A final reminder, if it is done incorrectly it can cost you far more than the savings you had from deciding not to use contractors. Know what you're getting into and form an informed opinion before undertaking this job.

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