Selleys VBS Vapour Barrier

What is Selleys VBS Vapour Barrier, and where should you use it?

Selleys Liquid Nails VBS is a highly cross-linked, two-pack epoxy moisture vapour barrier system. It is rolled onto a concrete floor slab to reduce the amount of water vapour emanating from the concrete, so that timber laid over the slab is not exposed to moisture coming up from below.

It is supplied as a 3.6L kit, which is sufficient for 20m², and it is normally a one-coat system. The mixed product is green, by design rather than by accident — the pigment lets you judge an even application by eye.

Two things to be clear about before you buy. First, this is a 100% epoxy product classified as HAZARDOUS and as Dangerous Goods — the resin is Class 9 (environmentally hazardous) and the hardener Class 8 (corrosive); neither component is a flammable liquid; it needs gloves, safety glasses and ventilation, and it cleans up with solvent, not water. Second, applying it is not the end of the job: Selleys states that after coating, floors should still be confirmed as having a moisture transmission rate of less than 15g/m²/24 hours before applying a flooring overlay.

Technical specification

Property	Typical result
Technology	100% epoxy
Colour	Resin is yellow; hardener is blue; green when mixed
Mix ratio	4 parts resin to 1 part hardener by volume (or 4.42 parts to 1 by weight)
Kit size	3.6L kit, sufficient for 20m²
Coverage	6m² per litre
Water vapour barrier	A 167 micron coating will normally achieve an MVT of less than 15g/m²/24 hours
Working time	20–30 minutes when poured out onto the slab
Cure time	Normally floors can be walked on, re-coated or adhered to in 8–12 hours at 25°C
Re-coat time	After curing and before 24 hours
VOC	68 g/L
Shelf life	12 months

Selleys asks that you contact them before using this data for the setting of specifications.

What the key numbers mean in practice

Coverage of 6m² per litre, and a 167 micron target film. Those two figures are the same requirement expressed differently — spreading a litre over 6m² is what produces a film around 167 microns thick, and that thickness is what normally achieves an MVT of less than 15g/m²/24 hours. Spread it further and you thin the film; thin the film and you lose the barrier. This is why the kit is sold as "3.6L, sufficient for 20m²" rather than as an open quantity: the area is the specification.

Working time is 20–30 minutes once poured out onto the slab, and the qualifier matters. The data sheet is explicit that you should not leave the mix in the can while brushing and rolling out, because doing so shortens the application time. Decanting the mix onto the floor keeps it cool and gives you a longer working window. An epoxy generates its own heat as it reacts, and a mass of it sitting in a can accelerates that reaction; spread thinly on a cool slab, it does not.

The same logic explains the instruction to keep VBS kits cool before mixing, and to have the whole area marked out and clear before you begin.

Cure of 8–12 hours at 25°C means this is normally an overnight product. That is a real planning difference from the rapid-cure alternative in the range, and it should be built into the program rather than discovered on the day.

Re-coat window: after curing and before 24 hours. Miss it and the process changes — if re-coating is required after 24 hours, the floor will need to be lightly sanded and wiped over with MEK solvent to ensure adhesion of the next coat. Plan the second coat, if you expect to need one, rather than deciding later.

Where to use it

• Sealing concrete floor slabs to reduce the amount of water vapour emanating from the concrete
• On concrete slabs prior to using Selleys flooring adhesives to lay timber overlay

Surface preparation

The data sheet notes that its guidance is a guide only, and that the installer should apply all Australian Standards, BCA/NZBC requirements and best practice.

• All surfaces must be clean, dry and sound, free of voids, loose materials and contaminants — curing compounds, oil, grease, waxes, sealers, previous coatings or adhesives. Complete removal must be carried out wherever contamination is suspected or evident.
• Preparation may be by diamond grinding, shot blasting, sand blasting or captive abrasive blast cleaning. Acid etching is not recommended, as the concrete then has to be neutralised and dried afterwards.
• Diamond grinding is the best preparation, because it removes high spots as well as laitance.
• The surface must be structurally sound and level. Concrete slabs shall be in accordance with AS2870-1996 Residential Footings and Slabs Code.
• For best results and optimum coverage, concrete surfaces should have a finish equivalent to that obtained when using a steel trowel.
• VBS can be applied if the concrete surface is dry and the slab has stabilised. To be stable, new concrete should be cured for at least 28 days, or until the moisture content of the slab is less than 5.5%.
• For application, use a 5–6mm mohair roller (or an applicator to minimise splatter) and cut in with a paintbrush.

How to mix it

For a full 20m² kit:

1. Keep the kit cool before mixing, and mark out approximately 20m² on the floor.
2. Pre-mix or thoroughly shake the hardener can before decanting.
3. Add the entire blue hardener component to the yellow resin component in the 4 litre can. Once blended, the mix is a uniform green. Streaks of yellow or blue demonstrate insufficient mixing.
4. Continue mixing for approximately two minutes.
5. Once thoroughly mixed and streak free, immediately pour the product out onto the floor over the marked area, in a way that allows an easy, consistent roll-out to an even build.

For less than 20m²: the kit has provision for a quarter mix, suitable for 5m² areas or for cutting in, using the separate mixing pail and stick supplied. Mark out the area, thoroughly mix each part in its own can, place the mixing stick in the one litre pail, pour resin in to the top of the yellow mark, then add hardener to the top of the blue mark, and stir to a uniform streak-free green.

Mixing less than a whole kit can also be done on a volume or weight basis: accurately measure out 4 volumes of resin and add 1 volume of hardener. Always ensure both components are thoroughly mixed in their own containers before decanting.

Getting the barrier right

The finish is the test. To be effective as a vapour barrier, the coated surface should be even, glossy and streak free. If the coating soaks away, gives dull patches, or if pinholes are visible, a second coat should be applied once the first has cured.

Selleys also gives a straightforward field check for dampness before you start: securely tape a 1m x 1m square of heavy duty plastic onto the slab and leave it for 24 hours. Visible dampness or discolouration under the patch when you remove the plastic is a warning sign.

Two structural situations that a coating cannot solve on its own:

• If the slab is below grade and the water table might be high enough to pressurise the concrete, perimeter drains would need to be installed.
• If the slab is still green and high in water-of-placement, let the excess water migrate out with good ventilation or a dehumidifier until the surface is dry.

Slabs known to be, or prone to, high moisture levels may require 2 applications. And after coating, confirm the result: test that the moisture transmission rate is less than 15g/m²/24 hours before applying the flooring overlay. Selleys recommends the anhydrous calcium chloride method (ASTM F1869-98) for that test. If less than 15g/m²/24 hours is not achieved, a second coat is recommended.

Limitations and important notes

• Very fast cure — for maximum working time, tip the product onto the slab immediately after mixing.
• Do not leave the mix in the can while brushing and rolling out, or the application time will be shortened.
• Two coats may be required on very porous concrete, or where there is high moisture content in the slab.
• Do not apply on damp or contaminated substrates.
• Not suitable for use below 10°C.
• Ensure adequate ventilation during use.

Safety — read this before opening the kit

VBS Vapour Barrier is classified as HAZARDOUS — it contains amine and epoxy resin, and it is classified as Dangerous Goods — the resin Class 9 (environmentally hazardous) and the hardener Class 8 (corrosive), neither being a flammable liquid.

• Wear gloves and safety glasses when using.
• Use in a ventilated area.
• Refer to the Safety Data Sheet for more detailed information. Separate SDS documents are published for the VBS resin and the VBS hardener.

Clean up and storage

Discard brushes and rollers after use. Clean up with acetone, MEK, epoxy or lacquer thinners — not water. This is a genuine difference from the water-based product in the same range, and it means having the right solvent on site before you start.

Store unopened containers below 30°C in a cool dry place away from direct sunlight. Unopened containers can be stored for 12 months from the date of manufacture.

Hazard classification

VBS Vapour Barrier is supplied as two separately classified components. Both are hazardous under Safe Work Australia GHS 7. The hardener is substantially the more dangerous of the two and carries the higher signal word.

Resin — signal word Warning.

• Acute toxicity, oral — Category 4. H302: harmful if swallowed.
• Eye damage/irritation — Category 2A. H319: causes serious eye irritation.

Hardener — signal word Danger.

• Skin corrosion/irritation — Category 1C. H314: causes severe skin burns and eye damage.
• Eye damage/irritation — Category 1.
• Sensitisation, skin — Category 1. H317: may cause an allergic skin reaction.
• Acute toxicity, oral — Category 4. H302: harmful if swallowed.
• Acute toxicity, dermal — Category 4. H312: harmful in contact with skin.

Both components are Dangerous Goods, in different classes. The hardener is Class 8, corrosive: UN 2735, packing group III, proper shipping name AMINES, LIQUID, CORROSIVE, N.O.S. (ISOPHORONE DIAMINE), Hazchem 2X. The resin is Class 9, miscellaneous: UN 3082, packing group III, proper shipping name ENVIRONMENTALLY HAZARDOUS SUBSTANCE, LIQUID, N.O.S. (EPOXY RESIN), and a marine pollutant. Neither component is classified as a flammable liquid.

What is in it

Resin

Chemical entity	CAS number	Proportion (w/w)
Diglycidyl bisphenol A resin	25085-99-8	>60%
Benzyl alcohol	100-51-6	10–30%
Non-hazardous or below reporting limits	—	Balance

Hardener

Chemical entity	CAS number	Proportion (w/w)
Isophorone diamine	2855-13-2	30–60%
Benzyl alcohol	100-51-6	1–10%
1,5-Pentanediamine, 2-methyl-	15520-10-2	1–10%
Non-hazardous or below reporting limits	—	Balance

H314 is the most serious classification on this page, and it is the reason the directions call for gloves and safety glasses rather than treating them as a formality. Severe skin burns is a chemical burn: between a third and two thirds of the hardener pouch is isophorone diamine, a strongly alkaline amine, and skin does not warn you about alkali the way it warns you about acid. There is often little immediate pain, so contamination gets left on the skin while the damage continues. The safety data sheet says outright that effects may be delayed and that the material can be absorbed through the skin, which is what the separate H312 dermal toxicity classification is recording.

The hardener is also a Category 1 skin sensitiser. Sensitisation is not irritation — it is the immune system learning the molecule, it is generally permanent once acquired, and afterwards much smaller exposures provoke a reaction. It builds from repeated casual contact rather than one soaking, which means the flooring contractor who mixes a kit a week is at more risk over a career than someone who spills a pouch once and washes it off properly.

Handle the mixed batch to the hardener's standard, not the resin's, until it has cured. And note what the Class 9 listing on the resin means in practice: it is a marine pollutant, so uncured residue and solvent washings should be collected and cured out rather than tipped into a drain.

Protection

• Face shield — the safety data sheet specifies a face shield, not just safety glasses, against a Category 1 eye hazard and a corrosive.
• Gloves — nitrile rubber is indicated for intermittent contact; assess suitability for your own conditions and glove construction.
• Clothing — overalls, apron and rubber boots. Wash contaminated clothing and protective equipment before storing or reusing.
• Ventilation — adequate ventilation throughout mixing and application.
• Emergency facilities — have water for irrigation available before you open the pouches. Fifteen minutes of flushing is a long time to improvise.
• Wash hands before eating, drinking, smoking or using the toilet.

First aid

Exposure	What to do
Eyes	Irrigate immediately with copious water for 15 minutes, holding the eyelids open. Remove contaminated clothing and wash the skin. Seek medical assistance urgently and transport to a hospital or medical centre. The product can cause corneal burns.
Skin	Effects may be delayed and the material can be absorbed through the skin. Remove all contaminated clothing immediately and flush skin and hair with running water — until told to stop by the Poisons Information Centre or a doctor, or for at least 15 minutes — then go to a doctor or hospital. For gross contamination, drench with water and remove clothing. Cover burns with a clean dry dressing. Do NOT break blisters.
Inhalation	Move the person to fresh air without becoming a casualty yourself. Remove contaminated clothing, loosen the rest, let them rest in whatever position is comfortable, and keep them warm. Seek medical advice if effects persist.
Swallowed	Rinse the mouth with water. Do NOT induce vomiting. Give a glass of water. Never give anything by mouth to an unconscious person. Call the Poisons Information Centre or a doctor immediately.

Tell the treating doctor that effects may be delayed and that the product can cause corneal burns; the safety data sheet says to treat symptomatically.

If poisoning occurs, contact a doctor or the Poisons Information Centre — 131 126 in Australia, 0800 764 766 in New Zealand — with the container to hand. Selleys emergency line: 1800 220 770 in Australia, 0800 220 770 in New Zealand.

Common questions about Selleys VBS Vapour Barrier

How much area does a kit cover?

The 3.6L kit is sufficient for 20m², at a coverage rate of 6m² per litre.

What is the mix ratio?

4 parts resin to 1 part hardener by volume, or 4.42 parts to 1 by weight. For a full kit, add the entire blue hardener to the yellow resin in the 4 litre can.

How long do I have to apply it?

20–30 minutes once poured out onto the slab. Do not leave it in the can while you work, as that shortens the time available.

When can I walk on it or lay flooring?

Normally floors can be walked on, re-coated or adhered to in 8–12 hours at 25°C.

Can I put a second coat on the next day?

The re-coat window is after curing and before 24 hours. After 24 hours the floor will need to be lightly sanded and wiped over with MEK solvent to ensure adhesion of the next coat.

How do I know one coat is enough?

The surface should be even, glossy and streak free. If it soaks away, gives dull patches or shows pinholes, apply a second coat once the first has cured.

Do I need to test the slab after coating it?

Yes. Confirm a moisture transmission rate of less than 15g/m²/24 hours before applying the flooring overlay, using the anhydrous calcium chloride method (ASTM F1869-98). If that is not achieved, a second coat is recommended.

How old does the concrete need to be?

New concrete should be cured for at least 28 days, or until the moisture content of the slab is less than 5.5%.

What do I clean up with?

Acetone, MEK, epoxy or lacquer thinners. Brushes and rollers should be discarded after use.

Is it hazardous?

Yes. It is classified as HAZARDOUS (contains amine and epoxy resin) and as Dangerous Goods — the resin Class 9 (environmentally hazardous) and the hardener Class 8 (corrosive), neither being a flammable liquid. Wear gloves and safety glasses, use in a ventilated area, and read the SDS.

What is the minimum application temperature, and how long does a kit keep?

It is stated as not suitable for use below 10°C. Unopened kits keep for 12 months from the date of manufacture, stored below 30°C in a cool dry place away from direct sunlight.

Is there a faster-curing alternative?

Yes — Selleys VBS Rapid is a water based two-pack epoxy vapour barrier in the same range, with a different cure time, coverage and clean-up method. Check its data sheet rather than assuming the two behave alike.

What goes on top of it?

Selleys flooring adhesives such as Timberflex or Direct Stick. Where a levelling compound follows, VP30 Primer is the bridging primer in the system.