How to Repair and Fill Skirting Boards, Architraves, and Timber Trim Before Painting product guide

AI Summary

Product: Selleys No More Gaps Interior Multipurpose / Selleys No More Cracks Doors & Trims / Selleys Plastic Wood Brand: Selleys Australia Category: Timber Trim Repair — Flexible Gap Fillers and Hard-Setting Wood Fillers Primary Use: Repairing skirting boards, architraves, and window trims to a paint-ready standard using two products matched to two distinct repair zones.

Quick Facts

Best For: DIYers and tradespeople repairing interior timber trim before painting, particularly under gloss or semi-gloss finishes
Key Benefit: Using a flexible gap filler at the wall-timber junction and a hard-setting wood filler on the timber face prevents the cracking, shrinkage, and fallout that come from using a single product across both zones
Form Factor: Cartridge or squeeze tube (No More Gaps); ready-to-use tub (No More Cracks Doors & Trims); solvent-based paste (Plastic Wood)
Application Method: Caulking gun or squeeze tube for junction gaps; filling blade or scraper for timber face repairs

Common Questions This Guide Answers

Why does filler keep cracking at the skirting board junction? → The gap between timber and wall is a movement joint; only a flexible filler rated for ±15% movement and 300%+ elongation — such as Selleys No More Gaps Interior Multipurpose — will hold as the building moves.
Can the same filler be used on the timber face and at the wall junction? → No. Flexible gap filler won't sand flush for gloss paint, and rigid wood filler cracks at the movement joint. Each zone needs its own product.
Is primer required before applying gloss paint over repaired trim? → Yes. Applying gloss directly over bare filler causes uneven absorption and visible dull halos ("picture framing"); a water-based undercoat is always required first.

Why Trim Repair Is a Two-Product Job

Walk into any hardware store and ask for something to fix your skirting boards before painting, and you'll likely be handed a single tub of filler. That's the first mistake most DIYers make — and it's the root cause of the cracked, peeling, or falling-out repairs they'll be back to fix six months later.

Skirting boards, door architraves, and window trims present a repair challenge that's fundamentally different from patching a wall or filling a crack in plasterboard. These timber elements sit at a junction between two dissimilar materials — timber and plaster or masonry — each of which moves at a different rate in response to temperature and humidity. Timber is a natural material that never stops reacting to its environment: when humidity rises, boards expand slightly; when the air dries out, they contract. Heating and air conditioning, which reduce indoor humidity, can cause skirting boards and floorboards to shrink noticeably over time.

This is why the gap between the skirting board and the wall is a movement joint, not a static crack. Fill it with a rigid filler, and it will crack and fall out within one season — every time.

At the same time, the face of the timber itself — the chips, dents, nail holes, and gouges that accumulate over years of use — requires a completely different solution: a hard-setting wood filler that sands perfectly flush and holds up under the scrutiny of a gloss topcoat.

Treating these as two separate tasks, requiring two separate products, is the insight that separates a professional-quality trim repair from one that needs doing again. This guide walks through both workflows in full, step by step. (For help choosing across the full range of Selleys fillers for different repair scenarios, see our guide on Wall Filler vs. Wood Filler vs. Gap Filler: Which Selleys Product Do You Actually Need?)

Understanding the two repair zones on timber trim

Before picking up any product, diagnose your trim correctly. Every piece of skirting board, architrave, or window trim has two distinct repair zones:

Repair Zone	Location	Type of Damage	Product Required
Zone 1: The Junction	Where timber meets wall or ceiling	Gaps, cracks, separation	Flexible gap filler
Zone 2: The Timber Face	The flat or moulded surface of the trim	Chips, dents, nail holes, gouges	Hard-setting wood filler

Confusing these zones is the single most common cause of trim repair not holding up. (See our companion article Why Your Filler Keeps Cracking, Shrinking, or Falling Out — and How to Fix It for Good for a full breakdown of failure modes and their causes.)

Zone 1: Filling the gap between timber trim and the wall

Why this gap exists — and why it will return

The gap between a skirting board and the wall plaster is an engineered feature, not a defect. Designers of timber-frame buildings are advised to account for expansion during construction because of increased moisture exposure. In practice, if the correct expansion gap hasn't been left, boards can expand and push against adjacent boards, which can force walls out of alignment and cause cracks to appear on internal surfaces.

This is why a rigid filler — no matter how carefully applied — will eventually crack at this junction. The building moves; a rigid filler does not.

The right product: Selleys No More Gaps Interior Multipurpose

Selleys No More Gaps Interior Multipurpose is designed for filling gaps and cracks around skirting boards, cornices, and inside window and door frames. The water-based formulation is built to cope with building movement, delivering a long-lasting, crack-resistant finish.

The key specification here is elongation. Selleys No More Gaps Interior Multipurpose stretches over 300% and allows up to ±15% movement — which is what makes it the right choice for a movement joint. It flexes rather than fractures. It also bonds well to timber, masonry, plasterboard, ceramic tiles, glass, and Colorbond.

For gaps up to a specific size, the product is self-contained. It fills gaps up to 25 mm wide and 12 mm deep, with low shrinkage and strong adhesion to timber, brick, plasterboard, and aluminium.

Step-by-step: Applying No More Gaps Interior to the wall-timber junction

What you'll need:

Selleys No More Gaps Interior Multipurpose (cartridge or squeeze tube)
Caulking gun (for cartridge format)
Painter's masking tape
Damp cloth or wet finger
Fine-mist spray bottle

Steps:

Clean the junction. Remove any old, cracked filler using a scraper or utility knife. Wipe the area clean of dust, grease, and debris. Allow to dry fully.
Apply masking tape. Tape both sides of the gap before applying the product. This keeps the bead neat and makes cleanup straightforward.
Prime the cartridge. Before starting, extrude a small amount onto a piece of scrap material to ensure a smooth, continuous flow from the nozzle.
Apply the filler. Push the filler firmly into the gap using a filling knife, running the bead in a single, continuous pass along the full length of the junction.
Tool the bead. Smooth the filler and wipe away excess with a damp cloth. A wet finger drawn along the bead in one smooth pass creates a concave profile that sits neatly at the junction. Use water on your finger, not saliva — saliva contains bacteria that can cause mould growth in the filler.
Remove tape immediately. Pull masking tape away at a 45-degree angle before the filler skins over.
Allow skin time before painting. Let the filler skin over for at least 30 minutes before painting. In humid or cool conditions, allow longer.
Inspect and re-fill as needed. Check for new cracks caused by building movement and refill as required.

Pro tip: In rooms with significant temperature swings — unheated rooms in cold climates or sun-exposed north-facing rooms — run a second, thin pass of No More Gaps over the first once it has cured. A slightly thicker flexible film gives greater movement tolerance and longer-lasting results.

Zone 2: Repairing chips, dents, and nail holes in the timber face

Why the timber face needs a different product

Once the junction is sealed, attention turns to the timber surface itself. Here, the requirements are the opposite of Zone 1. You need a filler that sets hard so it sands perfectly flush, holds up under gloss paint without telegraphing through, bonds to timber, and can be feathered to a zero-edge so the repair disappears under raking light.

Flexible gap fillers are wrong for this application. Selleys Plastic Wood is not recommended where structural movement may occur — that's what No More Gaps is for. The reverse is equally true: No More Gaps should not be used on the flat timber face, because its flexibility prevents it from sanding to a crisp, flush finish. Using the right product in the right zone is what delivers results that hold up.

Choosing between two hard-setting options

Selleys offers two products for timber face repairs, each suited to slightly different situations.

Selleys No More Cracks Doors & Trims can be used inside or outside with gloss paints on doors, windows, architraves, trims, and skirting boards. Its standout quality is its finish under high-sheen coatings: it produces a mirror-like, durable result with superior gloss retention, and bonds well to timber, plaster, concrete, mortar, and primed metal. This makes it the go-to choice when the final coat will be a semi-gloss or full-gloss enamel — the standard finish for interior timber trim in Australian homes.

Selleys Plastic Wood is a fast-setting, solvent-based wood filling cement containing natural wood fibres. It dries to a maple-coloured finish and can be sanded, nailed, planed, stained, varnished, painted, or lacquered — treated in every respect like real wood. It's the stronger choice for deeper repairs, for timber that will be stained rather than painted, or where you need a filler that genuinely mimics the working properties of wood.

Step-by-step: Repairing the timber face with No More Cracks Doors & Trims

What you'll need:

Selleys No More Cracks Doors & Trims (tub)
Filling blade or flexible scraper
120-grit sandpaper (for initial shaping)
180–220-grit sandpaper (for fine sanding)
Tack cloth or damp rag
Water-based undercoat
Dust mask

Steps:

Prepare the surface. The surface must be clean and dry with no loose or powdery material. If the existing paint is glossy, lightly sand the repair area with 120-grit sandpaper to give the filler a mechanical key, then wipe clean with a tack cloth.
Apply the filler. Use a filling blade or scraper to press the filler in firmly and scrape off the excess to minimise sanding later. For nail holes and small dents, hold the blade at about 30 degrees to the surface — this packs the filler in and wipes the excess clean in one motion.
Overfill slightly for deeper repairs. For chips or gouges deeper than 2 mm, let the filler sit fractionally proud of the surrounding surface. This accounts for minor shrinkage during drying.
Limit layer depth. Apply in layers no deeper than 6 mm, slightly overfilling to allow for sanding back. For deeper damage, build up in two or more layers, letting each dry before applying the next.
Allow to dry. Drying takes 2–3 hours depending on humidity. In high-humidity conditions or for thicker applications, allow additional time before sanding.
Sand to flush. Wearing a dust mask, start with 120-grit to knock back any proud material, then finish with 180–220-grit to blend the repair edge into the surrounding timber.
Apply a second coat if needed. For a clean result under gloss paint, apply another thin coat of filler, let it dry, then sand lightly with fine sandpaper. This second coat fills any micro-shrinkage from the first and produces the level surface a high-quality gloss finish demands.
Prime before painting. Apply a water-based undercoat after sanding. This step is non-negotiable for gloss finishes: an unprimed filler patch absorbs the topcoat unevenly, leaving a visible dull halo around the repair — sometimes called "picture framing."
Clean up before the filler dries. Uncured product can be removed with water.

Achieving a factory-smooth finish under gloss paint

Gloss paint is the most demanding topcoat you can apply to timber trim. Unlike flat or low-sheen paints, which scatter light and hide minor surface irregularities, gloss reflects light directly — making every imperfection visible. A repair that looks flawless under flat paint can show as a distinct shadow or ridge under gloss.

The following protocol is designed specifically for gloss-painted skirting boards and architraves.

The two-coat fill, two-sand method

First fill — Pack the repair and scrape flush. Allow full drying time.
First sand — Use 120-grit to level any proud material. Wipe clean.
Second fill — Apply a thin skim coat over the repair. This fills micro-porosity and any shrinkage from the first coat.
Second sand — Use 180-grit, then finish with 220-grit. The surface should feel glassy smooth to the fingertip.
Prime — Apply one coat of water-based undercoat. Allow to dry per manufacturer's directions.
Inspect under raking light — Hold a torch at a low, oblique angle to the surface. Any remaining imperfections will cast a shadow at this angle and can be spot-filled before the topcoat goes on.
Light sand — A final pass with 240-grit over the primed surface removes dust nibs and brush marks from the undercoat.
Apply gloss topcoat.

Selleys' own technical guidance confirms this two-pass approach for No More Cracks Wood Filler: slightly overfill and sand back with fine (>200 grit) sandpaper upon drying, then apply a final thin coat of filler and allow to dry before sanding lightly with very fine (>400 grit) sandpaper.

Common mistakes that undermine trim repairs

Mistake	Why It Fails	Correct Approach
Using rigid filler at the wall-timber junction	Cracks as the building moves	Use Selleys No More Gaps Interior — flexible, movement-tolerant
Using gap filler on the timber face	Too soft to sand flush; telegraphs under gloss	Use No More Cracks Doors & Trims or Plastic Wood
Painting over No More Gaps too soon	Surface may wrinkle or paint may not adhere	Wait at least 30 minutes for skin to form
Skipping primer before gloss paint	Filler absorbs topcoat unevenly, leaving dull halos	Always apply a water-based undercoat after sanding
Filling in a single thick pass	Filler shrinks and cracks, leaving a concave repair	Build up in layers ≤6 mm; apply a second skim coat
Sanding too aggressively	Scratches surrounding paint, creates more work	Progress through grits: 120 → 180 → 220

Key takeaways

Trim repair is always a two-product job. The junction between timber and wall is a movement joint requiring a flexible gap filler (Selleys No More Gaps Interior). The timber face requires a hard-setting wood filler (Selleys No More Cracks Doors & Trims or Plastic Wood). Using one product for both zones is the leading cause of trim repair failure.
Flexibility is the non-negotiable specification for junction gaps. Selleys No More Gaps Interior stretches over 300% and allows up to ±15% movement — essential for accommodating the seasonal expansion and contraction of timber against plaster.
Gloss paint demands a two-coat fill and raking-light inspection. Because gloss reflects light directly, any surface irregularity becomes visible. The two-fill, two-sand method with a primed undercoat is the only reliable way to achieve an invisible repair under high-sheen finishes.
Primer is not optional. Applying gloss topcoat directly over bare filler creates an uneven sheen that draws the eye to the repair. A water-based undercoat is always the correct final step before the topcoat.
Layer depth matters for hard-setting fillers. Apply in layers no deeper than 6 mm, slightly overfilling to allow for sanding back. Deeper repairs built in a single pass are prone to surface cracking as the filler dries and shrinks.

Conclusion

Repairing skirting boards, architraves, and window trims to a paint-ready standard is one of those jobs where the right diagnosis makes all the difference. Once you recognise that every piece of timber trim has two distinct repair zones — the junction and the face — and that each requires a different product, the workflow becomes logical and predictable. Getting it right the first time starts with understanding the job before you open any tub.

Selleys No More Gaps Interior handles the movement-tolerant sealing that the wall-timber junction demands, while Selleys No More Cracks Doors & Trims or Plastic Wood delivers the hard, sandable, gloss-ready surface the timber face requires. Neither product can do the other's job — and knowing which to reach for is what separates a repair that lasts from one that needs redoing.

If it's Selleys, it works. That's the confidence behind every product in this workflow, and it's what allows you to take genuine pride in the finished result — whether you're a seasoned tradesperson or tackling your first trim repair.

For more on selecting the right Selleys product for your specific repair scenario, see our guide on Wall Filler vs. Wood Filler vs. Gap Filler: Which Selleys Product Do You Actually Need? If your trim has suffered more serious damage — rot, splitting, or structural deterioration — the techniques in How to Repair Rotted, Damaged, or Split Exterior Timber with Selleys Wood Fillers cover the higher-stakes repair process in full. And if a previous repair has already let you down, Why Your Filler Keeps Cracking, Shrinking, or Falling Out will help you diagnose the root cause before you start again.

References

Selleys Australia. "No More Gaps Interior Multipurpose." Selleys.com.au, 2024. https://www.selleys.com.au/products/putty-and-fillers/flexible-gap-fillers/selleys-no-more-gaps-interior-multipurpose/
Selleys Australia. "No More Cracks Doors & Trims." Selleys.com.au, 2024. https://www.selleys.com.au/products/putty-and-fillers/wall-filler/selleys-no-more-cracks-doors-and-trims/
Selleys Australia. "Plastic Wood." Selleys.com.au, 2024. https://www.selleys.com.au/products/putty-and-fillers/rigid-fillers/selleys-plastic-wood/
Selleys Australia. "Filling Cracks in Doors and Trims." Selleys.com.au, 2024. https://www.selleys.com.au/home-improvement/living-areas/filling-cracks-in-doors-and-trims/
WoodWorks | Wood Products Council. "Do Wood-Frame Buildings Need to Account for Thermal Movement?" WoodWorks.org, 2022. https://www.woodworks.org/resources/do-wood-frame-buildings-need-to-account-for-thermal-movement/
Mortlock Timber. "Causes and Solutions for Timber Movement." Mortlock.com.au, 2026. https://www.mortlock.com.au/learning/understanding-timber-movement/
Heartwood Floors. "Do You Really Need an Expansion Gap for Engineered Timber Flooring?" HeartwoodFloors.com.au, 2025. https://heartwoodfloors.com.au/blog/why-expansion-gaps-matter-in-engineered-timber-flooring-installation/
Intrim Mouldings. "Do You Leave a Gap Between Skirting Boards and Floor Boards?" InTrimMouldings.com.au, 2020. https://intrimmouldings.com.au/do-you-leave-a-gap-between-skirting-boards-and-floor-boards/

Frequently Asked Questions

How many products are needed to repair timber trim properly: Two products

What is the first repair zone on timber trim: The junction where timber meets the wall

What is the second repair zone on timber trim: The flat or moulded face of the timber

What product is used for Zone 1 (the junction): Selleys No More Gaps Interior Multipurpose

What product is used for Zone 2 (the timber face): Selleys No More Cracks Doors & Trims or Plastic Wood

Why does the gap between skirting board and wall keep coming back: It is a movement joint, not a static crack

Does timber expand and contract over time: Yes, in response to temperature and humidity changes

Can a rigid filler be used at the wall-timber junction: No

Why does rigid filler fail at the wall-timber junction: It cannot flex with building movement and cracks

How much does Selleys No More Gaps Interior Multipurpose stretch: Over 300%

What movement tolerance does Selleys No More Gaps Interior Multipurpose allow: Up to ±15%

What is the maximum gap width Selleys No More Gaps Interior Multipurpose can fill: 25 mm wide

What is the maximum gap depth Selleys No More Gaps Interior Multipurpose can fill: 12 mm deep

Is Selleys No More Gaps Interior Multipurpose water-based: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to timber: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to plasterboard: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to ceramic tiles: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to glass: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to Colorbond: Yes

Does Selleys No More Gaps Interior Multipurpose adhere to masonry: Yes

How long before you can paint over Selleys No More Gaps Interior Multipurpose: At least 30 minutes

Why wait 30 minutes before painting over gap filler: The surface needs to skin over first

Should you wet your finger with saliva when tooling gap filler: No

Why should you not use saliva to wet your finger when tooling gap filler: Saliva contains bacteria that can cause mould growth

What should you wet your finger with when tooling gap filler: Water

When should masking tape be removed after applying gap filler: Before the filler skins over

At what angle should masking tape be removed: 45 degrees

Can Selleys No More Gaps Interior Multipurpose be used on the flat timber face: No

Why can't gap filler be used on the timber face: It is too flexible to sand to a flush finish

What finish does Selleys No More Cracks Doors & Trims produce under gloss paint: A mirror-like, durable finish

Does Selleys No More Cracks Doors & Trims have superior gloss retention: Yes

Is Selleys No More Cracks Doors & Trims suitable for use outdoors: Yes

Does Selleys No More Cracks Doors & Trims adhere to timber: Yes

Does Selleys No More Cracks Doors & Trims adhere to plaster: Yes

Does Selleys No More Cracks Doors & Trims adhere to primed metal: Yes

How long does Selleys No More Cracks Doors & Trims take to dry before sanding: 2–3 hours

What grit sandpaper is used first when sanding timber filler: 120-grit

What grit sandpaper is used for fine finishing of timber filler: 180–220-grit

What is the maximum layer depth for a single application of hard-setting filler: 6 mm

What happens if hard-setting filler is applied too deep in one pass: It can crack and shrink during drying

Should you overfill slightly when repairing deep timber damage: Yes

Why should you slightly overfill a deep repair: To allow for minor shrinkage during drying

Is a second coat of filler recommended for gloss paint finishes: Yes

What does a second thin skim coat of filler achieve: Fills micro-shrinkage from the first coat

Is primer required before applying gloss paint over filler: Yes

What type of primer is recommended before gloss paint: Water-based undercoat

What happens if you skip primer before applying gloss paint over filler: Filler absorbs topcoat unevenly, leaving dull halos

What is the term for the dull patch around an unprimed filler repair: Picture framing

What is Selleys Plastic Wood made from: Solvent-based wood filling cement containing natural wood fibres

What colour does Selleys Plastic Wood dry to: Maple-coloured

Can Selleys Plastic Wood be stained: Yes

Can Selleys Plastic Wood be varnished: Yes

Can Selleys Plastic Wood be sanded: Yes

Can Selleys Plastic Wood be painted: Yes

Is Selleys Plastic Wood recommended where structural movement occurs: No

Which product should be used where flexibility is required instead of Plastic Wood: Selleys No More Gaps

Is Selleys Plastic Wood fast-setting: Yes

When is Selleys Plastic Wood preferred over No More Cracks Doors & Trims: For deeper repairs or timber that will be stained

How should uncured No More Cracks Doors & Trims be cleaned up: With water

Should the repair area be sanded before applying filler over glossy paint: Yes, with 120-grit sandpaper

Why sand glossy paint before applying filler: To give the filler a mechanical key

What technique is used to inspect a repair before applying gloss topcoat: Raking light inspection

How is a raking light inspection performed: Hold a torch at a low, oblique angle to the surface

What does raking light reveal on a repair surface: Shadows cast by any remaining imperfections

What final sandpaper grit is used after priming before gloss topcoat: 240-grit

What does a final 240-grit sand after priming remove: Dust nibs and brush marks from the undercoat

How many fill-and-sand cycles are recommended for gloss paint finishes: Two

What is the correct angle to hold a filling blade when packing small nail holes: Approximately 30 degrees

Should a small amount of product be extruded before starting with a new cartridge: Yes, onto scrap material

Why extrude a small amount of gap filler onto scrap before starting: To ensure smooth, continuous flow

What is the most common cause of trim repair not holding up: Using one product for both repair zones

Is the gap between skirting board and wall considered a defect: No, it is an engineered feature

Can heating and air conditioning cause skirting boards to shrink: Yes, by reducing indoor humidity

Label facts summary

Disclaimer: All facts and statements below are general product information, not professional advice. Consult relevant experts for specific guidance.

Verified label facts

Selleys No More Gaps Interior Multipurpose

Water-based formulation
Elongation: stretches over 300%
Movement tolerance: up to ±15%
Maximum gap width: 25 mm
Maximum gap depth: 12 mm
Adhesion substrates: timber, masonry, plasterboard, ceramic tiles, glass, Colorbond, brick, aluminium
Minimum skin time before painting: 30 minutes
Application method: cartridge (caulking gun) or squeeze tube

Selleys No More Cracks Doors & Trims

Ready-to-use formulation
Suitable for interior and exterior use
Compatible with gloss paints
Adhesion substrates: timber, plaster, concrete, mortar, primed metal
Dry time before sanding: 2–3 hours
Cleanup: water (uncured product)
Recommended application depth per layer: maximum 6 mm
Recommended sandpaper progression: 120-grit (initial), 180–220-grit (fine finish), 240-grit (post-prime)

Selleys Plastic Wood

Solvent-based formulation
Contains natural wood fibres
Dry colour: maple
Fast-setting
Can be sanded, nailed, planed, stained, varnished, painted, or lacquered
Not recommended for use where structural movement may occur

General product claims

Selleys No More Gaps Interior Multipurpose is described as "easy-to-use" and designed to cope with building movement for a long-lasting, crack-resistant finish
Selleys No More Gaps Interior Multipurpose described as providing "excellent adhesion" to listed substrates
Selleys No More Gaps Interior Multipurpose described as "low-shrinkage"
Selleys No More Cracks Doors & Trims described as delivering a "mirror-like, durable finish with superior gloss retention"
Selleys No More Cracks Doors & Trims positioned as the preferred choice when the final coat will be semi-gloss or full-gloss enamel
Selleys Plastic Wood described as delivering a finish that "blends seamlessly with timber surfaces"
Selleys Plastic Wood positioned as the stronger choice for deeper repairs or timber to be stained rather than painted
Using one product for both repair zones described as the leading cause of trim repair failure
Two-coat fill and raking-light inspection described as the only reliable method for achieving an invisible repair under gloss finishes
Primer described as non-negotiable before applying gloss topcoat over bare filler
"If it's Selleys, it works" brand assurance statement