Large Gap Filler Kit — Single-Room (gaps over 5mm)

Not every project is a full renovation.

Sometimes it’s one deep gap that won’t stay filled.
A window frame letting in a draft.
A section of skirting that’s pulled away.
A stubborn joint that keeps cracking.

The Little Big Gap Kit is built for those deeper, problem gaps in smaller areas, the ones standard filler struggles with.

Why Standard Filler Fails

Wide gaps don’t behave like hairline cracks.

If you just pump filler into a deep void:

• It sinks

• It splits

• It wastes product

• It cracks later

That’s because gap filler is designed to bridge a small joint, not fill empty space.

This kit gives you the right system to do it properly.

When To Add Backing Rod

If your gap is larger than 5mm wide or deep, we strongly recommend adding closed-cell foam backing rod(available as an optional extra).

Backing rod:

• Controls sealant depth

• Prevents overfilling

• Reduces cracking

• Saves product

• Improves long-term durability

For smaller gaps under 5mm, you can usually seal directly.
For anything bigger, backing rod is the right way to set the joint up before sealing.

The Right Amount — No Overkill

We’ve paired the kit with compact 250ml bottles of:

• Prep-It to clean and improve adhesion

• Smooth-It to tool polyurethane cleanly

Plus paintable polyurethane gap filler, flexible, durable and suitable for larger internal gaps.

It’s enough to bridge the gap properly without buying bulk trade quantities you won’t use again.

This is a targeted repair kit, not a warehouse pack.

Ideal For

• Drafty window frames

• Door frames

• Skirting pulling away from walls

• Deep internal expansion joints

• Larger interior gaps that need flexibility

The Kit Includes

• 250ml Prep-It Surface Cleaner

• 250ml Smooth-It Lubricant

• 1 x Tube of Paintable Polyurethane Gap Filler

• Gap Sealant Applicator for a sharp finish

• 1 x Sponge

• 1 x Microfibre Cloth

• 2 x Timber Applicators

• Paper Towels

• Easy-to-follow instructions