Utes and 4WDs are loud inside. Big flat steel panels drum on corrugations, the exhaust drones on the highway and heat comes up through the floor. Sound deadening fixes most of it, and it's a job you can do yourself over a weekend. Here's what each product does, where it goes and how much to buy.
Three layers, three jobs
Think of it as a stack, from the metal up:
- Butyl sound deadener goes straight onto bare metal. It adds mass to the panel so it stops ringing and vibrating. This is what kills the tinny, hollow sound.
- Insulation or underlay goes over the deadener. It blocks airborne noise and slows heat getting into the cabin.
- Your floor covering goes on top: moulded carpet or vinyl, then Sandgrabba mats to protect it.
You don't have to do all three. Deadener on its own makes a noticeable difference to doors and floors. But if you're pulling the floor out anyway, do the lot.
Where to put it
Doors, floor pans, the firewall, the back wall of a cab, roof skins (metal roofs only), wheel arches and the cargo area. Focus on the middle of large flat panels. Overlapped and structural sections don't resonate much, so they don't need covering.
If you're doing the whole cabin, work from the top down: roof first, then the doors and arches, and the floor last so you're not kneeling on fresh butyl.
How much do I need?
The Car Builders Stage 1 box covers 1.8 m². As a rough guide:
| Area | Stage 1 boxes |
|---|---|
| Four doors, or a boot | 1 |
| A cabin floor | 2 |
| Floor plus boot or roof | 3 |
| A full car | 4 |
The HPP Stealth 10-sheet pack covers 1.5 m². Bigger cabins like a dual cab or a wagon with the cargo area done will need more, so measure first.
Heat: the other half of the problem
On a diesel ute, a lot of cabin heat comes through the floor from the exhaust and transmission tunnel, and through the firewall from the engine. HPP Stealth Mat is a 3 mm heat insulation rated to 800°C, made for exactly those spots. Under the bonnet, Car Builders under-bonnet insulation is a peel-and-stick 5.5 mm layer for the underside of the bonnet.
Underlay under new flooring
If you're fitting new moulded flooring, the underlay matters. Car Builders Stage 2 is a 10 mm peel-and-stick waterproof underlay that goes over the deadener. Dunlop Fibrefelt refibre under felt is the traditional option, sold as a half sheet for the front or a full sheet for front and rear. Either one helps the new floor sit flat and feel right underfoot.
How to fit sound deadener
- Strip back to bare metal. Seats, trims and the old floor come out.
- Clean every panel with wax and grease remover or methylated spirits. Butyl won't stick to dust or oil.
- Cut sheets to shape with a sharp knife or heavy-duty trim shears.
- Peel, stick and roll. Roll every sheet down hard, especially into floor corrugations. A roller makes a big difference to how well it bonds.
- Tape exposed edges with aluminium foil tape so the butyl doesn't grab clothes or bags.
The Car Builders install kit has the roller, knife and foil tape in one box.
Doing the floor? Do it once
The best time to deaden a floor is when it's bare, so if your carpet or vinyl is worn out, pair the job with new QMCC moulded flooring. It's made to order for your vehicle, in carpet or vinyl.
See the full range of sound deadening, insulation and underlay, or call 07 3340 4392 and we'll help you work out how much you need.
