Sash windows may look simple, but they’re precision-engineered systems that balance form, function, and heritage craftsmanship. While it can be tempting to tackle repairs yourself, DIY fixes can lead to bigger problems down the line.
Here’s why it’s best to leave sash window restoration to the professionals.
1. Risk of Damaging Original Timber
Older sash windows are often made from high-quality, slow-grown timber. Improper sanding, drilling, or fitting can split or crack the original frames - damage that may be irreversible.
Many DIYers also over-strip paint or use harsh chemicals that weaken timber fibres.
2. Rebalancing Is More Complex Than It Looks
Sash cords, weights, and pulleys must work in harmony. Replacing just one side or misaligning weights can cause:
- Jammed windows,
- Windows that won’t stay open,
- Increased wear on joints and seals.
Professionals have the tools and knowledge to rebalance sashes correctly for smooth, long-lasting performance.
3. Inappropriate Materials
Off-the-shelf fillers, sealants or paints are often incompatible with period joinery. For example:
- Silicone sealants can trap moisture,
- Modern paints may suffocate wood,
- Plastic putty can crack or pop out.
Specialists use breathable, heritage-friendly products designed to protect timber and maintain the building’s character.
4. Legal and Planning Considerations
Listed buildings and homes in conservation areas have restrictions. Replacing glass, modifying frames, or even repainting in the wrong colour could violate planning rules.
Professionals understand local guidelines and can carry out work in line with building regulations.
5. Glazing Mistakes Can Be Expensive
Whether you're installing double glazing or just reglazing a cracked pane, any errors in measuring, bedding, or sealing glass can result in:
- Leaks and draughts,
- Stress fractures,
- Failed glazing units.
A professional sash window company ensures proper fit, insulation and weatherproofing.
6. Loss of Heritage Value
DIY shortcuts might save money now, but poorly executed repairs reduce the visual and historic value of your property.
Future buyers - and surveyors - can tell the difference.
Final Thoughts
There’s a difference between basic upkeep (like repainting) and skilled restoration. Unless you have experience in heritage joinery, it's safer and more effective to hire professionals.
PM Windows has years of experience restoring timber sash windows across London – preserving beauty, integrity and function in every home we work on.
