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Musty smells · Mould · Damp floors

Subfloor Ventilation
Sydney

A damp, stagnant subfloor feeds musty smells, mould, rot and termites. We assess the moisture problem, design the right mix of vents and fans, wire it with our own electricians, and repair any timber the damp has already damaged.

✓ Vents & fan systems
✓ Wired in-house
✓ Timber repairs
✓ Drainage checked
AssessMoisture, airflow & drainage
DesignVents, fans or both
InstallBuilding + electrical in-house
RepairRotten timber replaced
Why it matters

What's under your floor affects the whole house

Homes with suspended timber floors rely on air moving through the subfloor to carry moisture away. Over time, vents get blocked by garden beds and paving, extensions and decks cut off airflow, and drainage changes send more water under the house. The subfloor turns humid and stagnant.

That moisture doesn't stay down there. It rises into the house as musty smells and mould on walls, wardrobes and furniture. Underneath, it rots bearers, joists and floorboards and creates exactly the conditions termites look for. Good subfloor ventilation keeps the space dry and stops all of that at the source.

Signs of a damp subfloor

  • Musty or earthy smell inside, especially in the morning
  • Mould on walls, ceilings, wardrobes or shoes
  • Floorboards cupping, swelling or feeling soft
  • White fungus or mould on subfloor timbers
  • Condensation or wet soil under the house
  • Blocked, few or no subfloor vents
  • Rising damp signs on internal walls
Solutions

Vents, fans or both?

OptionHow it worksBest for
Clearing existing ventsRemove blockages from garden beds, paving and debrisMild problems where vents exist but are covered
Additional passive ventsNew vent openings to improve natural cross-flowSubfloors with too few vents but open airflow paths
Mechanical fan systemFans and ducting create forced cross-flow, exhausting damp airClosed-in subfloors, extensions, low clearance, persistent damp
Drainage improvementsRedirect stormwater and surface water away from the subfloorPooling water or wet soil under the house

Most effective systems combine more than one. We design around your subfloor's layout, clearance and moisture source rather than installing a standard kit.

Process

How we fix a damp subfloor

Inspect

Moisture readings, airflow, vents, drainage and timber condition.

Design

Vent and fan layout matched to the subfloor.

Install

Vents cut, fans and ducting installed, wired by our electricians.

Repair

Rotten bearers, joists or boards replaced.

Check

System tested and set up.

One builder

Ventilation, electrical and timber in one job

A subfloor fan system needs building work (vent openings in brickwork, ducting, fan mounting), electrical work (a power supply, switching, timers or humidity control) and often carpentry to replace damp-damaged timber. Many ventilation installers subcontract the electrical or leave the timber for someone else.

We do all three in-house. Our licensed electricians wire the system and issue compliance certificates, and our carpenters replace damaged bearers, joists and floorboards. If stumps have failed, see restumping.

Related problems

Damp walls too?

A damp subfloor often goes hand in hand with rising damp in walls. Fixing one without the other can leave you with lingering damp. We assess both and recommend what's needed.

If termite activity is found, a licensed pest manager should treat it first. We then repair the termite damage and ventilate the subfloor to reduce the risk of them returning.
Subfloor inspection

Musty smell that won't go away?

Book a subfloor inspection. We'll find where the moisture is coming from and design the right fix.

Subfloor ventilation

Book an inspection

We'll call to arrange a time.

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FAQs

Subfloor ventilation questions

What is subfloor ventilation?
Subfloor ventilation moves moist air out from the space under a suspended floor and replaces it with drier outside air, using vents, fans or both, to keep the subfloor dry.
How do I know if my subfloor is too damp?
Signs include a musty smell inside, mould on walls or furniture, damp or cupping floorboards, mould or fungus on subfloor timbers, condensation and pooling water under the house.
Are more vents enough?
Sometimes. Where airflow is blocked by walls, extensions or low clearance, a mechanical fan system creating cross-flow is often needed.
Do subfloor fans run all the time?
Systems can run continuously or on timers and humidity controls depending on the design. We set up the system to suit the subfloor.
Who installs the fan wiring?
Our own licensed electricians wire mains-powered fan systems and issue compliance certificates, so no separate electrician is needed.
Does subfloor ventilation help with termites?
A dry subfloor is less attractive to termites and fungal rot. Ventilation is not a termite treatment, but it reduces the conditions they favour.
Can you fix rotten bearers and joists too?
Yes. Our carpenters replace damp-damaged bearers, joists and floorboards, and we can restump if stumps have failed.
What if water is pooling under the house?
Ventilation alone will not fix standing water. Drainage or stormwater issues need to be addressed first, and we assess this as part of the inspection.
Call 02 8107 9998