Restoring historic buildings requires a unique blend of craftsmanship, patience, and specialized knowledge. In a recent interview with Fine Homebuilding, Ben Brunick of Chalkstone Woodworking shared his expertise on window restoration, historic building rehabilitation, and the tools that make this painstaking work possible. Whether you are a homeowner with an older property or a contractor looking to expand your skill set, the techniques Brunick discusses offer valuable insights into preserving architectural heritage while meeting modern performance standards.
The Craft of Historic Window Restoration
Window restoration is far more than a repair job; it is a conservation discipline that respects the original materials and design intent of a building. Brunick, who runs Chalkstone Woodworking, specializes in bringing old windows back to full functionality while preserving their historic character. His work on a historic building that is being converted into a museum demonstrates the level of care and precision required.
Old windows, particularly those found in pre-war buildings, were often constructed from old-growth wood that is denser, more stable, and more durable than most lumber available today. Replacing these windows with modern vinyl or aluminum units not only sacrifices this superior material but also alters the building’s appearance and historical integrity. Restoration, by contrast, preserves the original joinery, glass, and hardware while addressing air leakage, operation issues, and decay.
Why Restore Instead of Replace
- Material quality: Old-growth wood used in historic windows has tighter grain and greater dimensional stability than modern lumber.
- Architectural integrity: Original window profiles, muntins, and glass contribute to the building’s character.
- Cost efficiency: Full restoration of a sound window can cost less than a high-quality replacement while lasting longer.
- Energy performance: Properly restored windows with weatherstripping and storm panels can perform as well as new double-glazed units.
- Sustainability: Keeping existing windows out of landfills reduces construction waste and the embodied energy of new materials.
Brunick’s approach involves assessing each window individually, determining whether the existing frame, sash, and glass can be salvaged, and then applying traditional techniques to bring them back to working order. This may involve repairing rotten sill ends, rebuilding sash corners, or replacing broken glass with compatible period-correct panes.
Essential Tools for Restoration Work
One of the most fascinating aspects of Brunick’s work is his use of both antique machinery and modern sharpening tools. He describes using a chain mortiser, a hollow-chisel mortiser, and a single-end tenoner for producing the complex joinery required in window restoration. These machines, many of them decades old, were built to last and remain highly effective when properly maintained.
Key Woodworking Machines for Window Work
| Machine | Purpose | Why It Matters for Restoration |
|---|---|---|
| Chain Mortiser | Cutting square or rectangular mortises | Produces clean, accurate mortises for sash joinery; handles deep cuts in dense old-growth wood |
| Hollow-Chisel Mortiser | Drilling square holes for mortise-and-tenon joints | Essential for reproducing original window joinery with tight tolerances |
| Single-End Tenoner | Shaping tenons on sash and frame components | Allows precise tenon sizing to match original dimensions and fit existing mortises |
| Table Saw with Dado Set | Cutting grooves and rabbets for glass and panel fits | Versatile for reproducing sash profiles and creating precise rebates for glazing |
Beyond these larger machines, Brunick emphasizes the importance of chisels and sharpening equipment. He uses diamond plates and diamond paste to achieve razor-sharp edges on his bench chisels. A sharp chisel is not just more pleasant to use; it produces cleaner cuts that require less sanding and produce better-fitting joints. For anyone working with historic woodwork, investing in a good sharpening system is one of the most important decisions you can make. Our guide to construction tools and their applications covers many of the essential implements for building and restoration work.
Sharpening Techniques That Make a Difference
- Start with a coarse diamond plate to establish a clean, flat bevel on the chisel edge. This removes any nicks or uneven wear.
- Progress through finer grits, working from coarse (300 grit) through medium (600 grit) to fine (1200 grit). Each step removes the scratches from the previous grit.
- Use diamond paste on a strop for the final polishing step. Brunick applies diamond paste to a leather strop to achieve a mirror finish that cuts through wood fibers effortlessly.
- Test for sharpness by shaving a thin wisp of end grain or slicing a piece of paper. A properly sharpened chisel should cut without tearing.
- Maintain between sharpenings by stropping regularly. A few passes on a strop every hour of use will extend the time between full sharpening sessions significantly.
Working with Divided-Light and Arch-Top Windows
A significant portion of Brunick’s work involves windows with divided lights and arched tops. These are among the most challenging elements to restore because they combine complex geometry with the need to match existing sightlines and profiles precisely.
Divided-Light Window Anatomy
Divided-light windows, also known as multi-paned windows, feature individual panes of glass separated by muntins (the thin bars that create the grid pattern). In historic construction, these muntins were an integral part of the sash structure, not merely decorative grilles. Each light was individually cut, glazed, and puttied, creating a distinctive look that modern snap-in grilles cannot replicate.
Restoring these windows requires the craftsman to understand the original construction sequence. The muntins typically have mortise-and-tenon joinery where they intersect, and the outer frame of each sash is joined with cope-and-stick or through-mortise joints. When a muntin has rotted or broken, the repair involves making a matching replacement with the exact profile, installing it with tight joinery, and matching the original paint or finish.
Window Joggles: A Traditional Reinforcement Detail
Brunick discusses the use of window joggles, an often-overlooked detail in historic window construction. A joggle is a projecting tenon or key at the meeting rail of a window sash that locks into a corresponding recess in the adjacent sash, helping keep the windows aligned and preventing sagging over time. When restoring historic windows, re-establishing or reinforcing joggles can dramatically improve the operation and longevity of the sash.
Handling Arch-Top Sashes
Arch-top windows present unique restoration challenges. Unlike rectangular sashes, the curved frame members must be steam-bent or laminated to achieve the correct radius. Brunick’s approach involves carefully measuring the existing arch, creating a pattern, and fabricating new curved components that match the original profile. The joinery at the junction of the curved and straight members requires precise fitting, often using bridle joints or custom splines.
If you are restoring a historic home with arch-top windows, it pays to work with a specialist who has experience with curved work. The geometry of these windows means even small errors in the arch radius will be visible and can prevent the sash from operating correctly. Understanding the role of period moldings and trim details helps restorers maintain the design language of the original building.
Restoration Beyond Windows: Preserving Historic Craftsmanship
Brunick’s expertise extends beyond windows. In the same interview, he describes restoring the antique pool table that was used by presidents in the White House, a project that demanded the same meticulous attention to detail as his window work. This breadth of experience highlights a key principle of historic restoration: the same skills, tools, and mindset apply across a wide range of preservation challenges.
Lessons from a Master Craftsman
Several principles from Brunick’s approach apply to any restoration project:
- Assess before acting: Every piece of historic fabric deserves a thorough evaluation before any work begins. What looks beyond repair may be salvageable with the right technique.
- Match the original method: Where possible, use the same joinery, materials, and construction methods used in the original. This ensures the repair ages similarly to the surrounding material.
- Invest in good tools: Sharp, well-maintained tools make the difference between a repair that looks original and one that looks like a patch. The chain mortiser and diamond sharpening system Brunick uses are investments that pay for themselves in quality of work.
- Understand the building’s history: Knowing when and how a building was constructed helps predict what you will find behind the paint and plaster. A late-19th-century building will have different window details than a mid-20th-century structure.
- Document everything: Taking measurements, photographs, and notes before and during the restoration creates a record that future caretakers of the building can reference.
Balancing Authenticity and Modern Performance
One of the ongoing debates in historic restoration is how to balance preservation of original fabric with modern energy performance and comfort. Brunick’s approach demonstrates that the two goals are not mutually exclusive. Weatherstripping can be added to historic windows in ways that are nearly invisible. Storm windows can be designed to complement rather than obscure the original sash. Interior shutters and period-appropriate blinds can add insulation while maintaining the room’s historic character.
For homeowners tackling a historic property, the key is to approach each decision with the question: what serves this building best over the next 50 to 100 years? Sometimes that means a full restoration of the original windows. Other times it means a sensitive repair that buys time until a more comprehensive restoration is feasible. For those considering a historic renovation project, our guide to balancing heritage and modern conveniences in renovation offers practical strategies for maintaining architectural character while updating functionality.
The Role of Concrete and Insulation in Historic Buildings
The interview also touched on concrete and insulation as they relate to historic building rehabilitation. In many older structures, the original foundation, basement walls, or flooring incorporate concrete that may need repair or upgrading. Similarly, insulation strategies for historic buildings must account for the fact that these structures were designed to breathe through their walls. Adding modern vapor-impermeable insulation without careful planning can trap moisture and accelerate decay of the original wood framing and masonry.
Specialists in historic restoration often use vapor-permeable insulation materials such as wood fiberboard, mineral wool, or aerated lime plaster. These materials allow moisture to move through the assembly while still improving thermal performance. When restoring a historic building, consulting with an engineer or architect who understands both historic construction methods and modern building science is essential.
Ben Brunick’s work at Chalkstone Woodworking exemplifies the craftsmanship and dedication required to preserve our architectural heritage. From restoring the windows of a future museum to sharpening chisels with diamond paste, every detail matters. Whether you are a professional carpenter or a homeowner with a century-old house, the principles he demonstrates offer a roadmap for treating historic buildings with the respect they deserve.