Hardwood Floor Gap Fillers: Which One Should You Use?
Choosing the Right Filler for Hardwood Floor Gaps
There are more types of wood fillers than most people realize — and they are not interchangeable.
The wrong filler cracks.
The wrong filler shrinks.
The wrong filler creates callbacks.
Start with one question:
Is the wood stable or unstable?
Before choosing a filler, understand what’s causing the gap.
👉 Why Hardwood Floor Gaps Happen →/pages/why-hardwood-floor-gaps-happen
Same-day shipping available.
Local pickup in Saint Paul.
Stable Wood + Large Area Filling
Use when:
• Gaps are small
• Floor is being sanded
• Humidity is consistent
• Boards are not independently moving
Duraseal Trowelable Wood Filler
Best for whole-floor trowel applications.
• Easy to spread
• Dries hard
• Sands easily
• Accepts stain and finish like wood
• Economical for large areas
• Available in multiple colors and sizes
Shop Duraseal Trowelable Wood Filler →
https://www.groundfloorsupply.com/product-page/duraseal-trowelable-wood-filler-gallon
Spot Filling Larger Gaps in Stable Wood
When voids are larger but boards are not moving:
Duraseal Wood Patch
Thicker than trowel filler. Less shrink.
• Designed for larger voids
• Precolored
• Sands easily
• Accepts stain and finish
• More body than standard trowel filler
Shop Duraseal Wood Patch →
https://www.groundfloorsupply.com/product-page/duraseal-wood-patch-gallon
Goodfilla Wood & Grain Filler
Thick, slightly expanding chemistry.
• Trowelable but dense
• Expands slightly while drying
• Counteracts shrinkage
• Dries hard
• Precolored
• Accepts stain and finish
Less shrink is the tradeoff for heavier spread.
Shop Goodfilla Wood & Grain Filler →
https://www.groundfloorsupply.com/product-page/wood-and-grain-filler-quart
Unstable Wood (Old Homes, Movement, Humidity Swings)
This is where most filler failures happen.
If boards move when you walk on them…
If humidity swings are wide…
If the species is unstable…
You need flexibility.
Troweling on Unstable Wood
Berger-Seidle Pak Stop + Pafuki Powder System
When mixed with water, Pafuki dries rock hard.
When mixed with Pak Stop, it dries to a flexible rubber-like mass.
Ideal for:
• Old pine floors
• Humidity-unstable homes
• Slight board movement
• Uneven subfloors
Important notes:
• Dry time depends on thickness
• Use foam backer rod for large gaps
• Sands harder than traditional fillers
• Not stainable — choose final color
This is a pro-level solution. Account for additional labor.
Shop Pak Stop →
https://www.groundfloorsupply.com/product-page/berger-seidle-pak-stop-filler
Shop Pafuki Powder →
https://www.groundfloorsupply.com/product-page/berger-seidle-pafuki-powder
Finished Flooring (No Sanding Planned)
You don’t always get to sand.
Flexible Spot Filling
Berger-Seidle Flex Fill Color
• Comes in standard caulk tubes
• Wide color range including greys and whites
• Extremely flexible
• Strong adhesion
• Works on finished and unfinished floors
Tape, mist lightly, apply, clean pull.
Not stainable — choose finished color carefully.
Shop Flex Fill Color →
https://www.groundfloorsupply.com/product-page/flex-fill-color-caulk
Small Hole Repair After Installation
Duraseal Wood Putty
Non-hardening putty for punch-list work.
• Press into nail holes
• Cleans with water
• Matches Quick Coat stain colors
• Ideal for minor imperfections
Every installer should keep a jar on the truck.
Shop Duraseal Wood Putty →
https://www.groundfloorsupply.com/product-page/duraseal-wood-putty-1-pound-jar
Quick Decision Guide
Ready to repair a stable gap?
👉 How to Fill Hardwood Floor Gaps (Step-by-Step)
https://www.groundfloorsupply.com/pages/how-to-fill-hardwood-floor-gaps
Stable wood + sanding entire floor → Trowel filler
Stable wood + larger gaps → Wood Patch or Goodfilla
Unstable wood + sanding → Pak Stop system
Finished floor + movement → Flex Fill Color
Tiny nail holes → Wood Putty
Wood Floor Filler FAQs
What is the best filler for hardwood floor gaps?
It depends on whether the wood is stable. Hard trowel fillers work for stable floors being sanded. Flexible systems are better for softwoods or humidity-unstable environments.
Will wood filler stop hardwood floors from moving?
No. All wood moves. Filler does not stop movement — it either accommodates it (flexible systems) or requires stable conditions.
Do wood fillers shrink?
Yes. All fillers shrink slightly. Flexible fillers like Pak Stop and Flex Fill shrink but do not crack. Hard fillers may crack if movement continues.
How long should wood filler dry before sanding?
Duraseal fillers dry in about 1 hour under normal conditions.
Flexible systems should cure at least 16 hours.
Deep gaps require extended dry time.
Hardwood Floor Gap Repair FAQs
How do I clean gaps before filling?
Remove loose debris with a knife or dull multitool. Vacuum thoroughly. Wiping alone is usually not sufficient to clean deep cracks.
Why did my filler crack?
Most cracking happens because the gap was seasonal or the filler was not pushed deep enough. Flexible systems are less likely to crack.
Do I need backer rod for hardwood floor gaps?
Backer rod is generally not recommended in tongue-and-groove flooring because it is easy to sand into and expose. Multiple applications are usually better.
Can I fill gaps without sanding the entire floor?
Yes, flexible caulk-style fillers can be used on finished floors for stable gaps. Tape carefully and allow full cure time.