Historic windows are the “eyes of a building” and add character that is significant to the design and aesthetic appeal of the architecture. When properly maintained and cared for, wood windows can last hundreds of years, which is why it’s crucial to make the right choices during the process of making repairs.
ABATRON is sometimes asked to consult on detailed wood repairs, so we’ve put together this checklist in order to make sure some important factors are considered.
A proper evaluation is key for a successful window repair.
- Paint Removal- Quite often, the need for window repairs stems from the need for a new coat of paint. Cracked, peeling, or flaking paint allows moisture and UV access to the wood, beginning a process of deterioration. It’s typically best to completely strip the paint, but several considerations should be made when removing it. Old fashioned scraping is typically the best process for historic windows. Chemical strippers can leave behind residues that need to be neutralized before repainting and excessive use of heat guns to loosen paint can break glass and even create harmful lead paint fumes. Pressure washing should be avoided because it will push water and fungal spores deep into the wood.
- Assessing the Wood and any Previous Repairs- Depending on when the window was last worked on, what you find underneath the paint is anyone’s guess. Good wood, decayed wood, old patches, putty, caulk, etc… Any loose, crumbling or delaminating wood or patches should be removed with a wire brush or Dremel tool. Soft wood that is still fairly stable can be saved by consolidation with LiquidWood®.
The wooden frame of these had a variety of previous repairs. Some were good. Some needed to be removed.
- Consider the Moisture- In order for proper epoxy repairs to be made, the wood being worked on has to be dry. A moisture content of 17% or less is preferred. This can be checked with a moisture meter. If there is too much water in the wood, the pores won’t properly accept LiquidWood and saturation with epoxy won’t be possible.
- Applying Consolidants (liquid hardeners) – Soft, porous or spongy wood can be hardened and restored with epoxy consolidants like LiquidWood. However- another common mistake that we’ve seen is using a consolidant as a protective coating, rather than as a treatment for decayed wood. Epoxy consolidants should be localized to the region where a decay zone exists or where an epoxy filler is going to be used. Coating large areas with LiquidWood creates a moisture barrier which can actually trap moisture and speed up the decay process. In pockets of deterioration where the soft wood is somewhat deep, small holes can be drilled down across the wood grain and then filled and refilled with LiquidWood to achieve saturation.
The decay zones at the base of the frame are saturated with >LiquidWood® consolidant.
- Applying Epoxy Filler – After saturating decayed areas with a consolidant, the missing material that has weathered away can be rebuilt with WoodEpox®, a two-part epoxy filler. Common mistakes for filling missing wood include using polyester products that shrink, water-based putties that can actually absorb moisture, or “rock hard” products that don’t allow for any movement once they set up. Changes in moisture levels and large temperature swings will make the wood naturally expand and contract. If the filler has no flexibility to match this natural movement, or if it has poor adhesive properties to begin with, the putty can loosen and fail over time. This can be avoided by ensuring that the filler being used to repair the cavity in the wood can accommodate the wood’s natural movement. WoodEpox is a shrink-free adhesive putty that will maintain its bond throughout the natural expansion and contraction of the wood that surrounds a repair.
Application of shrink-free WoodEpox® as a permanent wood replacement filler.
- Finishing the Filler – After applying WoodEpox, a common trick that saves significant time and effort is using alcohol, or other solvents to smooth the surface of the filler, reducing the amount of sanding and shaping you’ll have to do. A common mistake people make at this point is using water to do that smoothing. Water doesn’t evaporate quickly enough and can seep into the epoxy, causing curing issues and allowing for minimal shrinkage. It can also drastically increase the amount of time it will take for the epoxy to cure.
- Priming and Painting- After the repairs are made, choosing a high-quality exterior primer and paint is crucial to protecting the windows for the next several decades. Factors including location, temperature, elevation, and UV exposure all play a part in choosing the correct paint, so be sure to consult a local expert and remember that oftentimes, “you get what you pay for”. Paint is the biggest form of defense from the elements and will ensure that the repairs you’ve made will last as long as you’re hoping they do.
If you have further questions or if you need additional information on the epoxy wood repair process, please contact Abatron at 800-445-1754 or firstname.lastname@example.org.