Legal Requirements for Window Installation Complaints
Last updated: May 2026
When window installations go wrong—drafts, leaks, security issues, or poor fitting—you have strong legal rights under UK law. This guide explains exactly what contractors are legally required to do and how to force them to fix problems or compensate you.
Your Legal Rights Under UK Law
Consumer Rights Act 2015
This is your primary protection. The Act requires that all services (including window installation) must be:
- Performed with reasonable care and skill: The installer must be competent and use proper techniques
- Fit for purpose: Windows must actually keep out drafts, rain, and noise
- As described: If they promised "energy-efficient" or "soundproof," they must deliver
- Completed within a reasonable time: No endless delays or abandonment
đź’ˇ Key Point
Under the Consumer Rights Act, you have the right to repeat performance (force them to fix it) or a price reduction/refund if they can't or won't fix it properly.
Building Regulations 2010
Window installations must comply with Building Regulations, specifically:
| Regulation | Requirement |
|---|---|
| Part L (Energy) | U-values must meet minimum standards (typically 1.6 W/m²K or better) |
| Part F (Ventilation) | Adequate ventilation must be maintained |
| Part N (Glazing) | Safety glass required in certain locations |
| Part Q (Security) | Ground floor windows must meet security standards |
FENSA/CERTASS Certification: Installers should be registered with a Competent Person Scheme (FENSA, CERTASS, etc.) and provide a certificate proving compliance.
⚠️ No Certificate = Big Problem
If your installer didn't provide a FENSA/CERTASS certificate, your windows may not comply with Building Regulations. This can affect your property value and insurance.
Common Window Installation Problems
1. Drafts and Air Leaks
Legal Standard: Windows must provide adequate thermal insulation and weatherproofing.
What This Means:
- No cold air coming through gaps
- Seals must be intact and effective
- U-values must meet Building Regulations
Your Rights: Demand the installer returns to re-seal or replace faulty units.
2. Water Leaks and Damp
Legal Standard: Windows must prevent water ingress.
What This Means:
- No rain penetration around frames
- Proper drainage channels
- Correct installation of sills and flashings
Your Rights: Installer must fix leaks AND repair any damage caused (damp walls, mold, etc.).
3. Security Issues
Legal Standard: Ground floor windows must meet Part Q security requirements.
What This Means:
- Locks must be functional and secure
- Windows must resist forced entry
- Handles and mechanisms must work properly
Your Rights: Demand immediate repair—this is a safety issue.
4. Poor Fitting and Aesthetics
Legal Standard: Work must be performed with "reasonable care and skill."
What This Means:
- Frames must be level and square
- No visible gaps or damage
- Finish must be professional
- Must match what was agreed
Your Rights: Demand they redo substandard work.
Time Limits for Complaints
Short-Term Rights (30 Days)
Within 30 days of installation, you have the right to reject the work entirely if it's not satisfactory. You can demand a full refund.
Medium-Term Rights (6 Months)
For the first 6 months, the law assumes any defects existed at the time of installation. The burden of proof is on the installer to prove otherwise.
Long-Term Rights (6 Years)
You have up to 6 years to make a claim for breach of contract. However, after 6 months, you must prove the defect existed at installation.
đź’ˇ Guarantees and Warranties
Many installers offer 10-year guarantees. These are IN ADDITION to your statutory rights, not instead of them. You can claim under both.
How to Make a Complaint
Step 1: Document Everything
Before contacting the installer, gather:
- Photos of all defects (drafts, leaks, poor fitting)
- Videos showing problems (e.g., water coming in during rain)
- Your contract and any quotes
- FENSA/CERTASS certificate (or note if missing)
- Correspondence with the installer
- Evidence of damage (e.g., damp walls, mold)
Step 2: Informal Contact
Contact the installer by phone and email. Give them a chance to fix the problem voluntarily. Keep records of all communication.
Step 3: Formal Complaint Letter
If informal contact doesn't work, send a formal complaint letter. This must:
- Identify the problems: Be specific about each defect
- Cite your legal rights: Consumer Rights Act 2015, Building Regulations
- Demand remedies: Repair, replacement, or refund
- Set a deadline: 14 days to respond
- State consequences: Escalation to FENSA/CERTASS or court if ignored
Get a Professional Complaint Letter
Our expert resolution letters cite the exact legal requirements contractors must meet and force them to take your complaint seriously.
Start Your CaseStep 4: Escalate to FENSA/CERTASS
If the installer is registered with FENSA or CERTASS, you can escalate to their dispute resolution service. They can:
- Investigate the installation
- Order the installer to fix problems
- Award compensation
- Remove the installer from their scheme
Step 5: Small Claims Court
For claims up to ÂŁ10,000, you can use the small claims court. This is relatively simple and doesn't require a solicitor.
What You Can Claim
Direct Costs
- Cost of repairs by another contractor
- Refund of original payment (if work is rejected)
- Cost of temporary fixes (e.g., draft excluders)
Consequential Losses
- Damage to walls, carpets, furniture from leaks
- Higher energy bills due to drafts
- Cost of alternative accommodation if home is uninhabitable
- Loss of property value
Distress and Inconvenience
In serious cases (e.g., ongoing leaks causing mold and health problems), you may be able to claim for distress and inconvenience.
If the Installer Has Gone Out of Business
Insurance-Backed Guarantees
Check if your installer provided an insurance-backed guarantee. If so, contact the insurer directly.
FENSA/CERTASS Insurance
FENSA and CERTASS provide deposit protection and insurance for members. Contact them even if the installer has closed.
Section 75 Claims
If you paid by credit card (even just the deposit), your card provider is jointly liable. Claim against them under Section 75 of the Consumer Credit Act.
Frequently Asked Questions
Do I have to give the installer a chance to fix it?
Yes, you must give them a reasonable opportunity to repair the work before claiming a refund. However, if they've already tried and failed, or if the work is so bad it can't be fixed, you can reject it immediately.
What if I've already paid in full?
You can still claim a refund or compensation. Payment doesn't waive your rights.
Can I withhold payment?
If the work is incomplete or defective, you can withhold payment for the defective portion. However, you must pay for any satisfactory work completed.
What if the installer blames the manufacturer?
That's not your problem. You have a contract with the installer, not the manufacturer. The installer is responsible for providing working windows, regardless of whose fault it is.
How long do I have to complain?
You have 6 years from the date of installation to make a claim for breach of contract. However, it's best to complain as soon as you notice problems.
Take Action Now
Don't let faulty window installations drain your energy bills, damage your home, or compromise your security. You have strong legal rights—use them.
A professionally written complaint letter is the fastest way to force contractors to fix problems or compensate you for the damage.