Restoration Guide: Windows and Doors Replacement

Barbara Marquand

Editor's Note: This is article 4 of 12 in Chapter 4: The Windows and Doors Guide of Old House Web Restoration Guide. This guide was developed and edited for old homes from original materials in the U.S. Housing and Urban Development Rehab Guide.

Section 1--Overview

Wood was the main material used for window sashes and frames on old houses, but a new generation of materials--wood composite, fiberglass and reinforced or reformulated vinyl--have surpassed sales of wood frames. This section of the Windows & Doors volume of The Old House Web Restoration Guide discusses the pros and cons of the various types of frame materials available today and key factors to consider when repairing or replacing a window unit, sash and track, or frame.

Section 2--Materials for Window Frames

Why the move away from wood frames? New materials are stronger, last longer, require less maintenance, and provide as good or better insulating values. Here's a look at some of the options:

  • Engineered Wood: Generally composite or laminated wood, these materials don't twist along the grain, and they're stronger than wood, which allows for a narrower profile.
  • Fiberglass: Fiberglass, which is made of glass fibers, expands correspondingly to glazing materials, which cuts the stress on seals and the frame. Fiberglass can be used in varying climates and conditions because it resists corrosion, and it's available in dark colors that don't fade. Covered by a wood veneer, fiberglass can be used for a traditional look.
  • Vinyl: Vinyl provides a greater surface area for welding of corners, which provides a stronger connection. Low-density cellular vinyl has comparable R-values to wood, and high-density cellular vinyl, like fiberglass, features the highest R-values on the market.

2.1: Selecting Window Frames

Tired of mopping up pools from water condensation? Frames that reduce heat loss at glazing edges reduce the tendency for this problem. Note the overall U-value of a window, including the frame, when selecting units for remodeling. Because the frame takes up as much as a third of a window area, it has a major impact on overall performance.

The way windows are assembled is also important. Glass used to be available only in small panes, which were then joined together in a grid. Now a grid is no longer required, thanks to advances in glass technology, but it's still sometimes used for appearance. Today you have several options for preserving the look of a grid, from a window sash with individual panes--the most expensive and least efficient choice--to a single pane with simulated dividers, which provide a single surface to clean but preserves the look of a grid.

Section 3--Repairing and Replacing Your Window Frames

If they're not protected, wood frames can swell or rot. You can repair them, but first you should discover and correct the source of the problem, or your hard work won't pay off in the long run.

You don't have to replace an entire unit for your old house to benefit from new frame materials. Partial replacement, such as replacing the sash (panels that hold panes of glass) or installing an insulated glass insert, can preserve surrounding trim and save money.

3.1: Replacing the Window Unit

You'll get the best possible performance, longest lifespan for the remodeling, and the greatest chance for proper installation if you replace the whole window unit. However, this is the most costly alternative, and you'll have more wasted materials to discard than with a partial replacement or repair.

3.2: Replacing the Track and Sash

Replacement sash and track inserts come in kits and are available in a wide variety of sizes or can be custom made. Installation is fairly easy--a savvy do-it-yourselfer with some building experience can do it--and this type of replacement preserves the trim. But the window frame must be in good shape and relatively square for this option to work.

3.3: Installing Secondary Window Unit

This option provides a sash and track with a narrow frame to fit within the existing window frame. The secondary frame lets you benefit from new technology without tearing out everything. But secondary frames don't address leaks at the perimeter of the original frame, and they reduce the glazing area.

3.4: Replacing Windowsills

A wood windowsill is vulnerable to rot. You can correct the problem by using a sheet metal material as a cap over the existing sill (not the most sightly alternative) or invest in a replacement sill made from wood composites and vinyl. But make sure you're not merely hiding a more serious problem of rot that has infiltrated the wall.

3.5: Use Fillers and Epoxy Products

You can repair rotted or damaged wood frames with epoxy products. Epoxy consolidants penetrate and bind with wood fibers to prevent deterioration, and epoxy fillers repair holes and can be worked to look like wood. Epoxy fillers are good alternatives to solvent-based fillers because they don't shrink as they cure or come loose when materials expand or contract. Using epoxy products is the least disruptive way to rehab wood. But this course won't address the cause of the deterioration, which could affect adjacent areas, and you need a fair amount of skill to apply epoxy properly.

3.6: Shim Screws for Window or Door Frame Adjustments

You can use shim screws to adjust an out-of-square condition, a low-cost option that requires little effort. But an out-of-square opening could hint at a serious problem, such as a deteriorated structural member. Do a careful evaluation to avoid taking a short cut that could cost you time and money later.

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