Caulking Wherever You Need It: A Practical Guide
Where can you caulk?
Caulk can be applied anywhere that two materials join together, or where there are small gaps. In practice, caulking is most often found between windows, sideboards, and wet spaces like kitchens and bathrooms — but the range of useful locations is much wider than that, and so is the range of products.
The important principle is that caulks are often categorised by their intended application. There is no single product that is right everywhere. Damp areas require a sealant that is mould resistant and watertight, such as a silicone-based caulk. An exterior joint needs UV and weather resistance. An interior joint that will be painted needs to be paintable, which rules silicone out entirely.
This page works through the locations and what each one demands.
Wet areas — kitchens and bathrooms
These are the highest-demand locations in a house: constant water, daily temperature swing, and mould looking for a food source.
For the wet joints themselves — around baths, sinks, showers, splashbacks and shower screens — use a wet area silicone such as Selleys Wet Area Silicone, a neutral cure 100% silicone that delivers a waterproof and mould resistant seal that will not shrink, crack or peel away. It cures in 72 hours and should be tooled within 5–10 minutes of application.
For the dry gaps in the same rooms — around skirting boards, cabinets, cornices and inside window and door frames — Selleys No More Gaps Bathroom & Kitchen is the ideal solution. It is a water-based, paintable filler formulated to be water resistant, with a fungicide to protect against mould, and it is suitable for ceramics, glass, aluminium, plasterboard, wood, particle board and cement sheeting.
The distinction between those two is not optional. No More Gaps Bathroom & Kitchen's own technical data sheet carries a limitation that says it plainly: use Selleys Wet Area Silicone Sealant for gaps around baths, sinks and showers to create a waterproof seal. Water resistant and waterproof are different specifications, and the filler is not intended to be the thing keeping water out of a shower joint.
| No More Gaps Bathroom & Kitchen | Typical result |
|---|---|
| Technology | Water based |
| Colour / pack | White, 410 g cartridge |
| Application temperature | At least 5 °C |
| Skin time | 20 minutes |
| Paint over time | 60 minutes (gloss, sheen, low sheen); 180 minutes (flat, ceiling) |
| Joint movement capability | ±25% |
| Elongation (ASTM D412) | >200% |
| Shore A hardness | 25 |
Indicative data only, not intended for the preparation of specifications. To avoid paint cracking, apply to gaps no larger than 5 mm deep and 10 mm wide, at temperatures above 10 °C, and allow 24–48 hours before painting with oil-based paints.
Windows and exterior doors
Other common areas to caulk are the exterior windows and doors of your property. Sealants used on external parts will seal the space from draughts, water and insects.
Selleys No More Gaps Exterior is the water-based, paintable option for gaps and cracks around and between weatherboards, eaves, and exterior windows and doors. It uses a titanium compound to protect against UV and weather damage, and is suitable for timber and synthetic weatherboard, fibre cement sheet, brick, masonry and aluminium. It skins in about 30 minutes before painting, and needs to be protected from water for 24 hours to let it strengthen.
Where the joint will not be painted and needs maximum weather resistance — metal to metal, roofing, gutters and flashings — Roof & Gutter Silicone is the neutral cure exterior silicone, UV and weather resistant with a service range of −60 °C to +150 °C.
One caution on all exterior work: apply within the product's stated temperature window. Roof & Gutter Silicone must not be applied if the ambient or substrate surface temperature is below +5 °C or above +40 °C — which a dark roof reaches long before the air does.
For the interior side of a window, see how to fill gaps around windows.
Wood panelling and interior joinery
Caulk can be used to support the installation of wood panelling, and to seal the joints where panels meet walls, skirtings and architraves.
This is paintable-filler territory. No More Gaps Interior Fast Dry is designed for gaps and cracks around skirting boards, cornices and inside window and door frames, and is suitable for plasterboard, wood, particleboard, cement sheeting, aluminium and glass. Its skin time is 6 minutes and it is paintable in about 10 minutes with gloss and low sheen paints, 100 minutes under flat and 120 minutes under ceiling paints — apply at temperatures above 20 °C for those figures to hold.
Its joint movement capability is up to ±10%, for expansion joints where the depth is not greater than half the joint width — a narrower tolerance than a silicone, which is the trade for being paintable.
Drywall — filling holes and cracks
Caulk can also be used to fill holes or cracks in your drywall, providing insulation against draughts, water ingress and insect intrusion.
Worth distinguishing here: a crack at a junction — where plasterboard meets a cornice, an architrave or another sheet — moves, and wants a flexible filler. A hole or dent in the middle of a sheet does not move, and is better handled with a rigid wall filler that sands flush, since flexible fillers cannot be sanded.
Masonry, paths and structural joints
Expansion joints in masonry walls, patios, floors, fencing and concrete around the home are a category of their own, because they move more than most joints do. Brick & Concrete Silicone is rated at ±50% joint movement capability with 960% elongation at break, and is suitable for bricks and mortar, fibre cement, metal, ceramics, porcelain, concrete, marble and stone, wood and plastics including polystyrene.
Its limitations set the boundary clearly: not for below waterline applications, not for below ground applications, and not for polyethylene, polypropylene or Teflon.
Where not to caulk
- Weep holes and deliberate drainage gaps. Window frames and some cladding systems are designed to let water escape. Sealing those traps water inside the wall.
- Over live mould. An established colony can penetrate a new seal even where the new product contains mould inhibitors.
- Over old cured sealant. New sealant may not adhere well to it.
- Permanently submerged joints. Most of the silicone range explicitly excludes permanent water immersion.
- Joints you intend to paint, if you are using silicone. Silicone sealants are not paintable, and painting must be completed 7 days beforehand.
- Fire-rated penetrations, unless the product is fire-rated for that system. Fire resistance is a property of specific tested products, not of caulk in general.
Common questions about where to caulk
Where is caulking most commonly used?
Between windows, sideboards, and wet spaces like kitchens and bathrooms.
What kind of caulk does a damp area need?
One that is mould resistant and watertight — a silicone-based caulk.
Can I use a gap filler around a bath or shower?
Not as the waterproof seal. No More Gaps Bathroom & Kitchen's own data sheet directs you to use a wet area silicone sealant for gaps around baths, sinks and showers.
Can caulk be sanded and painted?
Water-based fillers can be painted after their stated paint-over time, and rigid wall fillers can be sanded. Silicone sealants can be neither.
What about outside the house?
Exterior windows and doors are common and worthwhile — sealants there keep out draughts, water and insects. Use an exterior-rated product, and watch the application temperature limits.
Can I caulk wood panelling?
Yes. Caulk supports the installation of wood panelling and seals the joints around it. Use a paintable interior filler.
Can I caulk cracks in drywall?
Yes, for cracks at junctions that move. For a hole or dent in the middle of a sheet, a rigid wall filler that sands flush is the better choice.
Which product for a concrete expansion joint?
Brick & Concrete Silicone — ±50% movement capability — but not below ground and not below waterline.
How small a gap is worth sealing?
Draughts, bugs and runoff water can enter through gaps as small as 1/64 inch, under half a millimetre.
How do I decide between products?
Start with whether the joint is wet, whether it will be painted, and how much it moves. See types of caulk.
What is the Selleys 'Where Can You Caulk' page about?
The page is a practical guide from Selleys Australia explaining the versatility of caulking, covering where and how to apply caulk—including windows, wet spaces, exterior doors, and wood paneling—and helping users find the right sealant for different parts of the home.
Which interior areas can be caulked around trim and fixtures?
According to the knowledge base, interior caulking can be done around skirting boards and baseboards, interior door frames, interior window frames, and cornices and ceiling trim.
Which bathroom and kitchen areas commonly require caulking?
Caulking is commonly applied around bathtubs and baths, kitchen sinks and basins, vanities and cabinets, shower screens and enclosures, and plumbing fixtures.
What exterior structural elements can be caulked?
Exterior caulking applications include exterior door frames and joints, exterior window frames and joints, walls, patios, and floors, fencing and expansion joints in concrete, and brick and mortar joints.
What materials are compatible with caulking products?
Caulking products can be applied to a variety of surfaces including ceramics and ceramic tiles, glass, aluminium and metal, wood and timber, plasterboard and drywall, concrete and brick, stainless steel and brass fittings, and plastic laminates and rubber.
What type of sealant is recommended for wet areas like bathrooms, kitchens, and laundries?
Specialized silicone-based sealants are recommended for wet areas such as bathrooms, kitchens, and laundries, as they create waterproof seals and help prevent mould growth.
What type of product is best for interior gaps in drier locations?
For interior gaps in drier locations, water-based gap fillers may be more appropriate than silicone-based sealants.
What are the four steps for using a caulking gun according to the page's HowTo guide?
The page's HowTo schema outlines four steps: 1) Become one with the caulking gun by understanding its barrel/cradle, plunger rod, and triggers; 2) Prepare the cartridge by cutting the tip off (secateurs work well) and cutting the nozzle at a 45-degree angle to the desired bead size, then insert it with the plunger rod pulled all the way out; 3) Apply the product by practicing on cardboard first, then gunning in a forward direction, pushing the product into the joint as you go; 4) Finish off the joint, often using soapy water for sealants (per manufacturer recommendation) or clamping glued joints in place until dry.
How long does the caulking gun how-to guide estimate the process takes?
The HowTo guide on the page estimates a total time of 60 minutes (PT60M) for the caulking gun process.
What tool is recommended for cutting the tip off a caulking cartridge, and why?
Secateurs are recommended for cutting the tip off a caulking cartridge because they work very well and are safer than knives.