How to Clean Sash Windows From Inside: A Simple Guide for Traditional Homes

If you’ve been searching for how to clean sash windows from inside, you’re not alone.

Traditional timber sash windows look beautiful, especially in Georgian and Victorian homes, but they need a different level of care compared to modern windows.

Many homeowners make the mistake of treating old timber sash windows like modern UPVC — and over time, that can lead to unnecessary damage, water retention and even rot.

The good news?

Cleaning sash windows from inside is often easier than people think once you understand how they work.

Understanding Traditional Sash Windows

Traditional sash windows are designed to slide vertically using cords and hidden counterweights.

Usually:

• The bottom sash slides upward
• The top sash slides downward

This clever design allows ventilation and makes much of the external glass accessible from inside the house.

However, over time many sash windows become:

• Painted shut
• Stiff or swollen
• Difficult to open
• Draughty or loose

If your windows feel difficult to move, avoid forcing them, especially with older timber frames.

What You’ll Need to Clean Sash Windows Properly

Before starting, it helps to have:

• Warm water
• Mild washing-up liquid
• Soft cloths or microfibre cloths
• Kitchen roll or dry cloth
• A soft brush for tracks
• A bucket

Avoid harsh chemicals or abrasive cleaning products, particularly on painted timber.

Older sash windows respond better to gentle cleaning methods.

Step 1: Open the Window Carefully

To clean sash windows from inside:

1. Carefully raise the bottom sash
2. Gently lower the top sash

This gives better access to both internal and external panes without leaning dangerously outside.

If the window sticks:

Do not force it.

Paint build-up, worn cords or timber movement may be stopping it from sliding correctly.

Step 2: Clean the Glass

Using warm water and a small amount of washing-up liquid, gently wipe down the glass.

For streak-free results:

Dry with a clean cloth or kitchen paper afterwards.

Avoid over-wetting timber frames during cleaning.

Too much moisture sitting around joints or sills is never ideal for older wood.

Step 3: Clean the Tracks and Frames

Dust and debris often collect in the sliding channels.

Use:

• A soft brush
• Hoover attachment
• Slightly damp cloth

Keeping the runners clean can help older sash windows move more freely.

When cleaning timber frames, always look for:

• Cracked paint
• Soft wood
• Water marks
• Small areas of timber decay

Catching problems early can often save expensive repairs later.

Avoid Modern Water-Fed Pole Window Cleaning on Timber Sash Windows

One mistake many homeowners make is using modern telescopic water-fed pole window cleaning systems, where large amounts of purified water are sprayed onto windows from the ground.

While this may work perfectly on modern UPVC properties, traditional timber sash windows are different.

Repeated soaking can:

• Leave water sitting on timber sills
• Encourage moisture around joints
• Speed up paint failure
• Increase the risk of timber rot over time

Traditional timber windows were never designed to be constantly saturated.

In our experience, traditional window cleaning methods are often the safer option for older sash windows, particularly in Georgian, Victorian and listed properties.

A careful hand clean helps prevent excessive moisture while also making it easier to spot early signs of deterioration.

Can Old Sash Windows Be Restored?

Absolutely.

Many homeowners assume older timber windows need replacing when in reality, they often just need restoring.

Established since 2005, specialists such as NJS Sash Windows regularly restore traditional timber sash windows suffering from:

• Rotten timber
• Broken sash cords
• Draughts
• Sticking windows
• Rotten sills
• Worn timber joints

Based near Stamford, work regularly covers Rutland, Peterborough, Cambridge and selected London restoration projects, including period and listed homes.

Final Thoughts

Learning how to clean sash windows from inside is not just about keeping glass clean — it is also about protecting traditional timber for years to come.

A little care, the right cleaning method and avoiding excessive water can help preserve original sash windows while keeping them looking their best.

If your windows are sticking, rotten or difficult to open, restoration is often a far better option than replacement.

Sash Window Repairs & Restoration

For enquiries contact NJS.

Call: 0749876833

Email: hello@njsash.co.uk