December 20th, 2014

How to Fix / Repair Rotten Wood

Determining the Extent and Solution for the Problem:

There are some problems with wood that just cannot be fixed. Rotten sashes on old windows may be better replaced than fixed, especially if they are costing hundreds in heating bills when new would save money over the long run. The following comments do not apply to this situation.

Using Fiberglass and Early Success:


One of my early successes was when a home owner asked me if I could repair a double sliding patio door. It was an 8 foot Anderson slider. There was a rotten spot, about the size of a nerf football just below the passive sash and the local dealer told him it would cost about $2,000 to replace the unit.

I had been experimenting with a product that promised to make life easier for repair people. It was a fiberglass product called Abtron. It had two parts, one a liquid and one a paste. I suggested we use it. I cleaned all the rot out of the cavity, mixed the liquid fiberglass (called a consolidant) part A with part B. and pained the inside. This liquid soaked into the wood and formed a bonding agent for the paste. Next I mixed the 2 parts of the paste and combined it with small pieces of wood, and forced it into the hollow. It was a hot day and it took about ½ hour for the hole to harden. I sanded the now filled opening a little and the house owner said he liked it. He asked how much he owed me and I told him $75, for which he gladly wrote a check. I never heard from him again, so I believe the operation was a success.

Abatron consolidant is not available in my local stores, so I buy it directly from the manufacturer. It is good for smaller projects because it saves time and money. For larger ones it becomes a good fastener.

Let me illustrate. If I have a window sill that needs to be replaced and should be painted after I fix it, it is often better, after I’ve cleaned the old piece and made a new one, to paint both joining surfaces with Consolidant, then “butter” the original one with fiberglass wood, then screw them together so the plastic wood oozes out a bit. Then I take a knife and cut off the excess. Finally I wet a putty knife and smooth what little plastic wood is visible. Often the result is good enough to paint when it cures. If not, I can add a little paste and sand a bit. The result is a fine smooth surface that must be painted, but will never rot again!

Replacing Rotten Wood with Aluminum Cladding over Treated Lumber

One day I was installing a 12 foot double patio door for a customer. The old one had had lots of rotten wood both in the doors and the frames. She wanted me to install the new vinyl door with aluminum cladding on the outside. I took off the old rotten wood and replaced with new #2 pine (white wood may be the new terminology in your area). The customer looked at my job when I was about done and told me she had heard in This Old House that it was necessary to use green treated lumber on this type of repair. I told her I knew Norm Abram would read the directions and my directions on the treated lumber told me not to use it under aluminum cladding. She insisted I change the wood and I did. I’m sure she found out after some time the aluminum had been eaten through by the acids in the treated lumber, but when the customer is wiser than the manufacturer, there is no help for the results.

Doing More than is Warranted:


Not long ago we were wrapping wooden window sills and brick molding on a substantial home. The customer asked my cladder to cover his windows right up to the glass. My man informed him that it was not customary to do that, but the customer insisted. The finished job looked striking and the cost was much less than installing new windows. The problem came when the spouse wanted to open the casement window and they could not. They called and asked what was wrong.

It’s obvious, I said. You cannot clad old sashes you wish to open without inviting trouble. Now the wrapping interferes with the frames. How would you like me to address it? Their suggestion was to follow the lead of my cladder and leave the operating sash without aluminum. Lesson: when a craftsman makes a suggestion, ask why before you override his idea. There may be a valid reason for his proposition.

Fixing Big Problems, but Saving Big Money:

I remember one job when we were looking at windows which were about 13 years old. The house had brick molding that was 6 inch and fluted. We discovered it had been installed without insulating the windows from the main frames of the house. Our approach was to replace only the rotten wood that was necessary, copying the fluting pattern of the original, consolidating and fiberglassing what was necessary, and remanufacturing details which were impossible to fix. It took three men three weeks to complete the project, but the cost was tens of thousands less than replacing all the relatively new windows.

Conclusion: There are times when fixing rotten wood is a good option, and there are times when the best course, least expensive over the long haul, is to replace the windows. Give me a call and we can work through the details together.

Phone: (608) 206-1082