Timber Surface Repair Guide

Repairing timber using modern resin systems is a cost-effective alternative to full replacement. This guide explains how professional decorators restore damaged wood to a "good as new" finish, saving you thousands on joinery costs.

What Does the Work Involve?

• Initial Assessment: Using a moisture meter and probe to identify the extent of rot or soft spots.
• Preparation: Removing paint and excavating all decayed wood back to sound, healthy timber.
• Stabilisation: Applying a liquid timber stabiliser (primer) to the remaining wood to ensure a permanent bond.
• Resin Application: Mixing and applying high-performance two-part epoxy or polyester resin to rebuild the profile.
• Shaping and Sanding: Once cured, the resin is sanded flush to match the original contours of the timber.
• Finishing: Priming, undercoating, and applying topcoats to protect the repair from the elements.

Typical Costs

Prices for timber repair vary based on the severity of the rot and the height of the work (e.g., ground floor vs. second-storey windows). Most specialists charge a premium for resin repairs compared to standard filling because the materials are significantly more durable and expensive.

Note: Prices include VAT at 20%. If your property is a "protected" building, costs may rise due to the specific materials and techniques required by local authorities.

Professional timber resin repairs are designed to move with the wood. Unlike cheap "plastic" fillers, these repairs won't pop out when the temperature changes.

How Long Does It Take?

• Small Patch Repairs: 2–4 hours (including curing time for fast-set resins).
• Single Sash Window Sill: 1 full day, allowing for thorough excavation and sanding.
• Entire Property Exterior: 3–7 days depending on the number of windows and doors affected.
• Curing Time: Modern resins can be sanded and painted within 1 to 4 hours, though some "deep-fill" systems require overnight curing.

DIY or Professional?

While DIY kits are available at major retailers, they are often polyester-based, which can become brittle and fail within a few seasons. Professional decorators use epoxy-resin systems (like Repair Care or Timbabuild) that remain flexible and chemically bond to the wood fibres.

If the damage is structural—such as a load-bearing beam or a heavily decayed window hinge point—you must hire a professional. Incorrectly applied filler can actually trap moisture, accelerating rot behind the repair.

Choosing the Right Tradesperson

• Specialist Certification: Look for decorators trained in specific systems like Repair Care or Window Care.
• Portfolio: Ask for "before and after" photos of previous timber restorations, specifically showing the sanding stage.
• Insurance: Ensure they have Public Liability insurance (minimum £1 million).
• Questions to Ask:
  • Do you use 2-part epoxy resin or standard builders' filler?
  • How do you check the moisture content of the wood before starting?
  • Will you provide a guarantee for the repair (typically 7–10 years)?

UK Regulations

• Listed Buildings: If your home is Grade I or II listed, you usually need Listed Building Consent for significant timber repairs. Like-for-like repairs are often permitted, but always check with your local planning office.
• Part L Building Regs: If you are replacing more than 25% of a "thermal element" (like a window), you may need to ensure the repair doesn't compromise the building's thermal performance.
• Waste Disposal: Professional trades must have a waste carrier licence to remove old, lead-based paint debris or rotten timber from your site.

Common Problems

• Trapped Moisture: Repairing wood with a moisture content over 18% will cause the resin to fail and the rot to continue.
• Incomplete Excavation: Leaving even a small amount of "soft" wood behind is like leaving a physical infection; the rot will spread under the new repair.
• Incorrect Mixing: 2-part resins must be mixed to the exact ratio; failure to do so results in "tacky" patches that never fully harden.
• Weather Conditions: Applying resin in high humidity or temperatures below 5°C can prevent the chemical bond from forming correctly.

Frequently Asked Questions

Can you repair timber that is currently wet?

No. The timber must be dried out first. A professional will use a moisture meter to ensure the wood is below 18% moisture content. If it's too wet, the resin will not bond, and the repair will fail within months.

How long will a resin timber repair last?

When performed correctly with professional epoxy systems, a repair can last as long as the surrounding wood—often 10 to 20 years. Most specialists offer a 10-year guarantee on the bond itself.

Is it cheaper to just buy a new window?

Rarely. A new high-quality timber sash window can cost £1,500–£2,500 per unit. A comprehensive resin repair typically costs between £300 and £600, representing a significant saving.

Can I paint over the repair immediately?

Most professional resins are "paint-ready" within 2 to 4 hours. However, you must use a high-quality primer-undercoat designed for non-porous surfaces to ensure the paint adheres to the resin.

Do I need to remove the whole window to repair the sill?

Usually, no. Most timber repairs are carried out in situ. This avoids the mess and cost of removing internal architraves and potentially damaging the surrounding plasterwork.