Underfloor / subfloor ventilation
Custom-designed subfloor ventilation across the Northern Beaches and North Shore. Professionally sized systems, EC or AC motor fans, automated control, and a licensed electrician's certificate on completion. Complete systems from $2,090 inc GST.
Why it matters
Renovations, decks, garden beds and paving block the original airbricks. The subfloor stops breathing, moisture sits against the timber, and the damp air finds its way upstairs — up to 40% of the air inside your home originates under the floor.
With no airflow, the subfloor holds moisture against the timber — the ideal conditions for damp and decay.
Stagnant subfloor air doesn't stay under the house — it works its way up into the living areas.
Bearers, joists and floors are the costliest part of a home to repair. Keeping them dry is far cheaper.
That's why every system here is automated — a 7-day timer as standard, humidity-driven control if you want it.
Free instant quote
Property type, what you're noticing, the size of the floor area and how you want it controlled. Takes about 60 seconds.
The builder prices your system live — fans, ducting, grilles, timer or smart control — all inc GST, supply and install.
A few phone photos of the outside and switchboard and Daniel confirms the fixed price, usually the same day. No site visit.
No payment, no obligation, no sales visit. Prices shown before you give us a single detail about yourself.
What it could cost
Most Northern Beaches homes land in the two- or three-fan range. The instant quote builder tells you exactly which one suits your subfloor and what it costs.
1-fan system
$2,090
to $2,325 inc GST
Small — a few rooms over subfloor (up to ~40 m²)
2-fan system
$2,975
to $3,445 inc GST
Average home (~40–90 m²) — most common
3-fan system
$3,850
to $4,555 inc GST
Large home (~90–150 m²)
4-fan system
$4,730
to $5,670 inc GST
Very large (150 m²+)
What's included
Daniel assesses your subfloor from your photos — moisture signs, existing ventilation gaps and your property's specific needs — and confirms a fixed price before anything is booked. Fan and vent positions are then confirmed with you on site before any drilling.
Every system is professionally sized, mapped, and documented — including fan placement, airflow direction, intake and exhaust locations, and wiring routes. You receive a copy of the system design for your records.
We install variable speed fans with your choice of high-efficiency EC motors (ultra-quiet, low energy) or AC motor fans — sized to suit your subfloor volume and ventilation requirements.
Your system is set up with automated run schedules controlled from your phone, so your ventilation runs when it's needed most — no manual intervention required.
We return after three weeks to inspect fan operation, check airflow performance, and make any adjustments to ensure your system is working at its best.
We don't disappear after the install. Marmont Electrical provides ongoing support for your subfloor ventilation system, including maintenance advice and system checks.
The benefits
Trapped moisture under your home creates the perfect environment for mould, mildew, and fungal growth — all of which can affect your indoor air quality and your family's health. A properly designed subfloor ventilation system continuously circulates fresh air through the crawl space, removing excess moisture before it becomes a problem. This is one of the most effective solutions for homes experiencing musty smells, damp floors, or visible mould in subfloor areas.
Excess subfloor moisture is one of the leading causes of timber floor damage, bearer and joist deterioration, and termite activity in Australian homes. Timber substructures that remain damp are significantly more vulnerable to rot and pest infestation. Installing underfloor ventilation protects your home's structural integrity, reduces the risk of costly repairs, and can help maintain your property's long-term value — particularly important for older homes across the Northern Beaches.
Up to 40% of the air inside your home can originate from the subfloor space. If that air is damp, stale, or carrying mould spores, it directly affects the air your family breathes every day. Subfloor ventilation installation significantly improves indoor air quality by replacing stagnant, moisture-laden air with fresh, dry airflow — reducing allergens, odours, and respiratory irritants. This is especially important for homes with family members who suffer from asthma, allergies, or sensitivities to mould and dampness.
Build a free instant quote and see the fixed price for your subfloor — no payment, no obligation.
Recent work
Why Marmont
We don't guess — every system is sized, mapped, and documented based on your property's unique subfloor conditions. You receive a full system design for your records.
All wiring, fan installation, and control systems are installed by a licensed electrician — not a handyman or ventilation-only company. Contractor Licence 470836C.
We return three weeks after installation to check fan performance, inspect airflow, and make any adjustments — included in every install at no extra charge.
Based in Frenchs Forest, we understand the specific moisture and ventilation challenges that affect homes across the Northern Beaches and North Shore — from coastal humidity to bushland drainage.
FAQs
Complete systems start from $2,090 inc GST for a single-fan system and $3,445 inc GST for the recommended 2-fan EC system that suits most homes. That price covers supply and installation — fans, weatherproof external grilles, a new weatherproof power point, 7-day timer control, full testing and CCEW electrical certification. Your final fixed price is confirmed from your photos before anything is booked.
No. Photos of each side of the house, the subfloor access point and your switchboard are enough for Daniel to confirm a fixed price — usually the same day. Fan and grille positions are then confirmed with you on site before any drilling.
EC (electronically commutated) motors use up to 70% less energy than AC motors, run significantly quieter, and offer precise variable speed control — ideal when the system runs for long periods. AC motor fans are a proven, cost-effective option with strong airflow, well suited to timer-based schedules or tighter budgets. Both options are the same system; only the motors differ.
Most residential subfloor ventilation systems are installed, tested and certified in a single visit. Larger homes and multi-unit blocks are scheduled around the system design.
No. The fans are IP-rated subfloor units installed under the floor, and EC motors are near-silent when turned down. Speeds are tuned on site so you don't hear the system running.
Yes. Every system includes a 7-day timer as standard, and you can upgrade to the SAL Pixie smart switch for Bluetooth app control or Clipsal Wiser humidity automation, which runs the fans automatically off real subfloor moisture readings.
Yes. Blocks are engineered per site — fans shared between units, passive fresh-air intakes, a dedicated protected circuit and full certification. Send photos and plans and Daniel will design and price the whole system. We've completed blocks of 10+ units.
Every install is carried out by a licensed electrical contractor (Licence 470836C), tested, issued with a CCEW electrical certificate, and backed by a lifetime workmanship warranty. A 3-week post-install inspection is included at no extra charge.
Service areas
Based in Frenchs Forest and installing underfloor ventilation throughout:
Your quote
Pick your system, add a few phone photos, and Daniel confirms the final price — usually the same day. No payment now, no site visit needed.
Pick your property type above to get started.
Photos are how Daniel confirms your price without a site visit — a quick lap of the house with your phone is all it takes.
One photo of each side of the house at ground level — it shows the walls, vents and where the grilles can go.
A photo through the access door or hatch is gold — but only if it's safe and easy. Skip it if not.
One photo of your switchboard with the door open — it tells Daniel everything about your power setup.
No payment now — you're requesting a fixed quote. Daniel confirms your final price from the photos before anything is booked. Fan and vent positions are confirmed with you on site before any drilling, and every install is tested, certified (CCEW) and backed by a lifetime workmanship warranty.
