Can I improve a wall without taking it down?

Usually yes. The sheet is bonded over the existing face, joints overlapped and taped, every edge sealed, then overboarded with 12 mm plasterboard. That adds about 20 to 30 mm per face. Whether it is worth doing depends on what the wall already weighs.

How much difference will it make to my wall?

On a lightweight partition, a great deal: the manufacturer’s assembly data takes a bare steel-stud wall from STC 33 to STC 51 with 3 mm MLV added within it, both laboratory values. On a 150 mm concrete wall, effectively none. Weigh the existing construction first.

Can I use it on an outdoor boundary fence?

Only with a designed, weather-protected detail, and only if the fence is continuous and sealed along its whole length. A gap at the base or between panels caps the result at around 20 dB no matter what is added. An unsealed fence is a screening problem, not a barrier problem.

Will it improve an existing machine enclosure?

Often, but in the right order. If the panels are thin steel that rings when struck, bond BlastVib BB460 to them first — the panel itself is the radiator. Then close the openings, then add mass. Adding mass to a ringing, leaking enclosure is money in the wrong order.

Does adding MLV affect a fire-rated wall?

Adding any material to a rated assembly is a question for the project’s approving authority, since the rating belongs to the tested system rather than to any one product. Where a fire requirement applies, specify BB830FR, which was independently tested to AS/NZS 1530.3:1999, SGS report AJFTS26000525R01_EN of 3 February 2026, indices 0/0/0/7, with none of the six specimens igniting. Put the assembly question to the authority.

How do I know whether the wall is even the problem?

Listen along it on a night when the noise is present, pausing at the middle of the wall, the door edge and undercut, every penetration and socket, and directly under the ceiling line. If any of those is louder than the middle of the wall, that is where the money goes first.

Improving an existing wall, fence or enclosure without rebuilding it

The question this page answers

You already have the barrier. A partition wall between two offices, a party wall in a townhouse, a boundary fence, a plant room, a machine enclosure that was built before anyone thought about noise. It is not good enough, and demolishing and rebuilding it is either impossible or absurdly expensive. Can it be made to perform better as it stands, and is that worth doing?

Sometimes yes, decisively. Sometimes no, and the money belongs somewhere else entirely. The difference is almost always settled by one number, and it is a number you can work out before you talk to anybody: how much the existing construction already weighs per square metre.

Weigh what you already have

Under the mass law, each doubling of mass per unit area buys roughly 6 dB. So the value of adding about 5 kg/m² depends entirely on what it is being added to. On something light it is a large proportional change. On something heavy it is nothing.

Approximate mass of common construction, and what adding about 5 kg/m² of MLV is worth
Existing barrier	Approximate mass	Is adding MLV worth it
12 mm plasterboard, steel studs, 12 mm plasterboard	about 20 kg/m²	Yes. The largest proportional gain available, and the case the assembly data below describes
Single-skin plasterboard on studs, one face only	about 10 kg/m²	Yes, but boarding the open face first is usually the better first spend
1.5 mm steel enclosure or guard panel	about 12 kg/m²	Only after damping it. A thin steel panel radiates because it rings — treat that first with BlastVib BB460
Metal or fibre-cement boundary fence	about 10 to 15 kg/m²	Only if the fence is sealed along its whole length and tall enough to break line of sight. Weather exposure is the real limit
100 mm autoclaved aerated concrete block, plastered	about 70 to 90 kg/m²	Worthwhile against speech, much less so against bass
100 mm dense concrete block, plastered	about 200 kg/m²	Marginal. The door, the penetrations and the ceiling void will each give more
150 mm dense concrete	about 250 to 400 kg/m²	No. This is a rounding error. Do not buy MLV for this wall

What the assembly data actually shows

A bare steel-stud partition is STC 33 and the 3 mm sheet on its own is STC 32, according to the manufacturer’s datasheet, reference BB830/20/v2. Adding the sheet within the wall takes the assembly to STC 51. That is a much larger step than the mass law alone would predict, because a limp layer inside a cavity does more than add weight — it also disrupts the resonance of the board-cavity-board system. All of these are laboratory values from the manufacturer, and field performance is normally 5 to 10 dB lower.

STC by assembly, manufacturer data, laboratory values
Assembly	STC
3 mm MLV alone, material only	32
12 mm plasterboard, steel studs, 12 mm plasterboard, no MLV	33
As above, with 3 mm MLV added within the wall	51
3 mm MLV plus 50 mm mineral wool in the cavity	53
3 mm MLV to both faces, 50 mm mineral wool	56
Double stud, separate frames, 50 mm cavity, mineral wool	68

Read that as an order of priority, not as a promise about your wall. Mass first, cavity absorption second, structural separation last — the biggest gain, and the one that costs floor area as well as money.

How to add it without rebuilding

Close and seal the openings first: door undercuts and perimeters, service penetrations, the ceiling void at the wall line, gaps at the base. Then listen again.
On thin steel, bond BlastVib BB460 to the panel to stop it ringing before adding any mass over it.
Bond BB830 over the existing face with BA990. Clean, dry substrate. Concrete, block, steel, timber and plasterboard all take it.
Overlap the sheets at every joint and tape them closed. A butt joint left open is a line source of the noise you are paying to stop.
Seal head, base and both sides with BA890, and back every socket and switch box with BA650.
Overboard with 12 mm plasterboard and seal the board perimeter again before finishing. The added build-up is about 20 to 30 mm per face.

A 5 m² roll weighs about 25 kg, which matters overhead and on a lightweight existing frame. Check that what you are fixing to will carry it before you order, particularly on a fence, a suspended ceiling or an old enclosure.

What not to do

Do not add mass before closing the openings. It is the most common way to spend a budget and hear no difference.
Do not bond the sheet with a rigid construction adhesive. A rigid bond makes a solid bridge across the layer you are trying to isolate; BA990 is formulated to stay flexible.
Do not screw or rivet the sheet through to the frame more often than the fixing schedule requires. Every rigid fixing is a path across the layer.
Do not leave the sheet exposed outdoors and expect it to last as a fence lining. It is UV-resistant, but an external application needs a designed, weather-protected detail, not a sheet stapled to a fence.
Do not add a second layer over an unsealed first layer. Sealing the first is worth more than doubling the material.
Do not assume the sheet upgrades a fire-rated wall. Adding any material to a rated assembly is a question for the approving authority; where a fire requirement applies, specify BB830FR and put the question to them.

Where the honest answer is not to buy

The wall is already heavy — dense block or concrete. Adding about 5 kg/m² to 250 to 400 kg/m² changes nothing you will hear. Spend it on the door, the glazing and the penetrations.
The dominant path is not the wall. A door, a window, a duct, a ceiling void or the floor slab. Improving the wall next to the real path improves nothing.
The perimeter cannot be sealed, because of access, services or a finish that cannot be disturbed. Without a sealed perimeter the layer will not return what it costs.
The problem is impact or structure-borne — footfall, machine feet, a subwoofer on the slab. Mass added to a barrier does not intercept these paths at all.
The problem is reverberation inside one space. That is absorption, a different material entirely.
The target is strict and below roughly 125 Hz. Mass alone is weak there; that job needs cavity depth and structural separation, which means rebuilding after all.

Buying in Thailand

THB including 7% VAT, excluding VAT in brackets. MLV is sold in whole 5 m² rolls only.
Item	Unit	Price
BB830 mass loaded vinyl	per m²	1,122 (1,049)
BB830, full roll	5 m² roll, about 25 kg	5,612 (5,245)
BB830FR, where a fire requirement applies	per m²	1,288 (1,204)
BB830LF, formulated for low frequency	per m²	1,761 (1,646)
BlastVib BB460 damping, for thin steel	per roll	8,688 (8,120)
BA990 adhesive	per cartridge	428 (400)
BA890 sealant	per cartridge	321 (300)
BA650 putty pad	per pad	385 (360)

Stock is held in Bangkok and dispatched within one working day of cleared payment. Delivery is free nationwide over THB 20,000 excluding VAT, otherwise THB 500 in Bangkok and the surrounding provinces or THB 900 upcountry. Delivery is within Thailand only. A pre-cut 1 m² trial piece is available for testing a fixing detail on an unusual substrate before committing to a project quantity.