Rotted frame on aluminum clad wood window

Why Aluminum Clad Wood Windows Rot

The benefits of Aluminum Clad Wood Windows

Aluminum clad wood windows were very popular in the 1990’s & early 2000’s. You can still find them being installed today on New Construction and during window replacements on existing homes. The wood casement windows looked high-end. You could stain or paint them to match the interior design. The aluminum cladding on the outside of the wood frame eliminated the need for a Homeowner to have to paint & maintain the outside of the window. At first, these windows seemed to be the Builders’ and Homeowners’ choice. Over time, the public and most Builders have steered away from them due to their rot problems and are now favoring vinyl windows.

How moisture travels through a wood window

During the winter months, the inside of a home typically has moist warm air. Based on Building Science, this air wants to travel to cold dry air. The path of least resistance is through the wood frame of the window. On 100+ year old homes, the wood in the windows were made of old growth lumber which made them very strong and rot resistant. These older homes can go decades with peeling paint and still show no signs of rot. Newer windows from approximately the 1980’s forward are typically made of soft pine that rots very fast especially if not maintained. If you have newer wood window and they are properly maintained with stain or paint, then the wood frames can hold up really well for decades. With wood frames that have aluminum cladding, it doesn’t matter how well a Homeowner maintains the windows. They will rot and here’s why: The aluminum cladding on the outside of that frame prevents moisture from escaping into the outside air. So in the cold winter months, moisture becomes trapped in that soft Pine frame causing it to rot.

Rotted out frame found on Home Inspection in Omaha
Rotted out frame behind the aluminum cladding

Rain absorbs into the wood frame

Most Homeowners aren’t aware that the caulk sealing the aluminum cladding to the wood frame typically dries up within a few years. You can take a spray bottle with water in it to the outside of the glass and watch the water disappear behind the aluminum cladding at the base of the window. That’s how you know the caulk has dried up. I recommend taking clear Silicone window/door caulk and applying it between the base of the glass and the aluminum cladding. This will re-seal that gap that’s allowing rain to soak into the window frame and extend the life of your window. If you have a hail storm and the hail impacts the aluminum cladding, this can open up that seal between the aluminum cladding and the wood window frame leading to rot too. These hail impacts should be part of your hail claim to replace your windows for 1 simple reason: The window manufacturer won’t stand behind their warranty if the window is damaged by hail. If it’s not part of a hail claim, then I recommend to the Homeowner to apply that Silicone as noted above as preventative maintenance.

The frame was so rotted out that the aluminum cladding was falling off of the window.
The frame was so rotted out that the aluminum cladding was falling off the window

How to find the rotted frames

Aluminum clad wood window with rot in bottom corner found by pushing in aluminum cladding
Aluminum cladding pushes in along bottom corner of rotted wood frame

Looking at the aluminum clad wood windows won’t find the rot. If the casement window opens, then obviously look and feel for rot in the bottom corners. To find the rot from the outside though, you will need to physically push in on the bottom corners. If the frame is not rotted, then the aluminum won’t move. If it is rotted, then the aluminum cladding will push right in at the corners. If it’s extremely rotted, the aluminum cladding will push in all the way across the entire bottom or start to fall off…which is when you can actually see the rot behind it. I recently had a Home Inspection in West Omaha on a 20-year old house with 15 rotted windows. To find all of them, I had to lug a 24′ ladder around the house and push in on each window. That many windows adds up to a lot of money when that Contractor shows up to replace them. Depending on the Contractor, the bids can range from $300 per window up to $1,500 per window. If your house has custom windows, then the price will most likely be on the higher end.

Another rotted frame found by pushing in on the aluminum cladding
Entire bottom frame is rotted out when you can push in the aluminum cladding in the middle of the bottom