Old windows need more than a fresh coat of paint. Before you begin, check whether the existing finish is loose, whether the wood is sound, and whether water has reached vulnerable joints or sills. These checks help you spot repairs that should happen first and avoid sealing in damage. Work carefully, especially on older painted surfaces: paint applied before 1978 may contain lead, so use appropriate precautions and consult a qualified professional if you are unsure.
Look for Failing Paint
Check the frame, sash, muntins, and trim for paint that is peeling, blistering, cracking, or lifting at the edges. Run a hand lightly over the surface; chalky residue can signal a finish that has weathered. Pay attention to layers that separate from one another, since painting over loose material usually leads to early failure. Do not scrape or sand old paint until you have considered the possibility of lead.
Note where the paint is failing rather than treating every side of the window alike. Exposed corners, lower sash rails, and areas with direct sun or frequent wetting may deteriorate faster. If paint is failing mainly near a joint or sill, look for a moisture source before repainting. Addressing leaks, poor drainage, or persistent condensation can help protect the new finish.
Check the Wood for Damage
Inspect the sill, lower sash, exterior trim, and joints for soft, swollen, split, or crumbling wood. Dark staining, open seams, and wood fibers that appear damaged can indicate prolonged moisture exposure. Press gently with a small blunt tool only where appropriate; sound wood should resist, while decayed areas may yield. Avoid probing fragile historic details or removing material just to test it.
Look closely at the sill’s slope and the points where it meets the frame and exterior wall. Standing water, failed caulk, or gaps can let moisture enter and damage concealed wood. If you find rot, extensive softness, or movement in a joint, plan for repair before painting. Paint can protect sound, dry wood, but it cannot restore wood that has already decayed.
Inspect Joints and Glass Edges
Examine corners, glazing putty, and the narrow edges where glass meets the sash. Cracked or missing putty can allow water into the sash and leave glass less secure. Check for gaps between trim and siding, failed sealant, and open joints around the frame. Use compatible repair materials and preserve original profiles when possible; excessive caulk can trap water or obscure details.
Look for paint bridging moving joints or covering drainage paths. Sashes should move without scraping heavily, and channels should remain clear. Do not paint over hardware, weatherstripping, or weep openings. If the window sticks, identify whether paint buildup, swollen wood, or a mechanical problem is responsible before applying another coat.
Prepare a Careful Work Plan
Before choosing a preparation method, determine the age of the window and whether its paint may contain lead. Older homes can have lead-based paint beneath newer layers. Avoid dry sanding, power sanding, or aggressive scraping until the risk has been assessed. Follow applicable safety requirements, protect occupants and nearby surfaces, and use a lead-safe professional when the work calls for specialized containment or cleanup.
Once the surface is safe to prepare, remove only paint that is loose, clean the window, and let damp wood dry before priming. Repair damaged wood and glazing first, then select primer and topcoat suited to the substrate and exposure. Keep a written list of defects and repairs so each area receives the right treatment. For complex historic windows, Ann Arbor Heritage Paint can help assess the work before repainting.
A careful inspection helps distinguish a paint problem from moisture damage, failed glazing, or a window that needs repair. Check the entire assembly, address the cause of deterioration, and take lead precautions before disturbing older paint. If you find extensive wood damage or are unsure how to prepare the surface safely, consider arranging a professional assessment.