The choice of finishes for internal and external woodwork used to be fairly simple because the options were somewhat limited. Nowadays though, you have a bewildering range of products at your disposal to suit just about every situation.
However, the most common question people have is not the choice of finish but whether it should be oil or water-based and, which is best?
The obvious answer is, of course, ‘it depends’ but most people already know a few of advantages and disadvantages.
- Water-based paints dry quicker and you can wash your brushes with water; they’re also more pleasant to use and have less odour.
- Oil-based paints are smelly, take a long time to dry and cleaning brushes out afterwards is a real pain.
Based on what we already know then, water-based paints should be the obvious choice; so what’s the problem?
There is a perception that water-based paints are not as hard-wearing as their oil-based counterparts but this is not correct. In fact, they can perform much better because they stay flexible for longer. And this is especially important when used externally.
External timber will expand and contract in response to local temperatures, especially when exposed to direct sunlight. Eventually, this everyday movement will break down a painted surface allowing moisture to penetrate below the surface.
Because water-based paints remain flexible they can accommodate regular movement and, therefore, last much longer.
Water-based paints tend also to be water vapour permeable (or, microporous), which means they allow trapped moisture beneath their surface to evaporate naturally without damaging the paint film. Some oil-based paints also have this property but only those specially formulated for exterior use
Internally, flexibility isn’t so important but resistance to knocks and scrapes is. Oil-based paints take longer to dry initially but they set hard within a couple of days, so tend to be better in this regard.
Water-based paints dry quickly but take a long time to fully cure, sometimes it can take a few weeks. This means you have to be extra careful until the paint has completely hardened.
In the short-term then, oil-based paints may be better although, longer term, water-based paints can be just as tough.
Although all household paint must now contain a minimal amount of volatile organic chemicals it is generally true that water-based paints contain much lower levels than oil-based alternatives. They have less odour and are safe to use provided there is sufficient ventilation.
Oil-based paints are also technically safe to use but good ventilation is essential during application and for a few days afterwards, at least.
This is where oil-based paints excel since it’s easy to rub-down between coats and to build up layers of gloss to get a mirror-like finish. And, because oil-based paints take longer to dry, you can work the paint for longer to smooth out any brush marks and achieve a uniform finish.
Water-based paints, even those labelled as gloss, do not have such an advantage. They tend to dry slightly ‘flat’ and, because they take a long time to fully harden, can be difficult to sand-down in order to get a smooth finish.
Also, because they dry quickly, they can be difficult to brush over large areas. To paint a door, for example, you’ll get a better result using a fine roller and then finishing with a brush, but the surface will still dry slightly stippled or with some evidence of brush marks.
Oil-based paints contain alkyd resins which are prone to yellowing over time. White gloss paint is particularly susceptible, especially where there are low levels of natural sunlight.
Water-based paints contain synthetic resins which are not light sensitive, so will stay white for much longer.
So it all depends then?
So yes, there isn’t a simple right or wrong answer, it all depends what result you want to achieve?
Generally speaking though, water-based or ‘quick-drying’ paints have a lot of advantages and should be your first choice, especially for exterior woodwork.
If you want an ‘old-school’ high gloss finish though, oil-based paints are hard to beat.
Anne – How do I know if existing paintwork is water or oil based?
Darren – Unless you have expereince of using different paint finishes it’s going to be difficult.
Characteristics of an oil based finish are typically less visible brush marks, a highly reflective surface and slight yellowing over time, depending on whether the surface has been exposed to direct sunlight or not.
Water-based finishes have a flatter surface with little or no reflection and more visible brush marks. Thyme are not prone to yellowing.
Laura – can you thin gloss down?
Darren – Yes. With water-based paint which is often labelled as ‘quick-drying’ you can simply add a few drops of water.
For solvent-based gloss (the smelly stuff) a few drops of white spirit or turpentine substitute will do the trick.
Joanna – Hi, we’ve just had a painter in who has painted our banister using an acrylic eggshell. When he came to quote for the job he said he was going to use a bin sealer first and then apply the paint, Read more…
however when he came to do the job he said he’d read up about the paint and he didn’t need to do this. We’ve since had a new carpet laid and the paint is literally coming off when you touch it. Is there anything we can do now to stop this? I am at my wits’ end!! Thanks!
Darren – Water-based paints such as acrylic eggshell take a while to fully harden, sometimes 2-3 weeks, and are very susceptible to scratches and peeling during this process. A proper tradesman would know this.
Obviously, not everyone wants to wait a few weeks before laying new carpet and it should be expected the paintwork will be damaged to an extent. It is standard procedure to go back and make good any damage after carpets have been fitted. It really depends if the damage goes beyond what one would normally expect (on average, a few minor scuffs and scratches here and there).
If proper preparation hasn’t been carried out, which is likely, the problem will be much worse than this though.
I can’t really comment on the episode with the banister since I’m not sure what the problem was? It does sound like you’re dealing with an idiot though and hopefully lessons have been learned.
Jane – I bought oil based undercoat by mistake and have already painted a door frame with it. If I sand it down well is it ok to use my water based gloss on it please? I’ve been reading about adhesion problems.
Darren – The problems usually arise from the fact that the solvents in oil-based paints take a long time to cure but if you leave it a couple of weeks you shouldn’t have any issues. It may be that you need an extra coat of gloss to get a decent finish but that isn’t a bad thing really since it will be more durable over time.
Louise – We have bought a shop that is in a flood area, we’ve had it re-plastered and have been advised to use an oil based paint, is this necessary or would a masonry paint suffice? We want to be able to just wash down the walls if we/when we do get flooded
Using oil-based paints to mitigate damp problems is a sure-fire way to make any problems worse, not better. I’m a bit confused as to whether this is an internal or external wall you’re talking bout but the advice is still the same. Use a water-based masonry paint externally and a water-based emulsion with no vinyl content (such as Dulux SuperMatt) internally.
Neither option helps you much in regards to wash-ability but, I think, this is of less importance than encouraging a build-up of internal damp which is what using oil-based paints will achieve?
The reason for this is because water will always find a way into the fabric of the building via hairline cracks, defective seals around openings, loose or broken pointing, etc. This is perfectly natural and allowing this moisture to escape via evaporation is the best practice. Oil-based paints will impede this ability, trapping moisture and causing no end of issues.
Rebecca – Hi there. We have extensive yellowed oil based gloss in our hallway, stairs and landing and we want to paint over it with water based satinwood. Read more…
We have previously used water based eggshell (white) on skirting elsewhere in the house, but I find the finish too flat, so switching to satinwood. Have done a bit of research and am I tending on keying the surface with sand paper, applying water based Johnstone’s aqua undercoat and then two coats of Johnstone’s aqua satinwood. Researching it has been so overwhelming as there’s so much advice out there. There such an enormous amount of gloss to cover, including banisters and spindles, so j don’t want it to peel, chip and flake. Does what I have planned sound like the right thing to do?
Darren – Preparation is key to long term results so ensure all surfaces are thoroughly washed-down and rinsed with clean warm water to remove any greasy or oily residue.
Use a fine abrasive paper and aim to remove as much glossiness as practicable from previously painted surfaces. Obviously with spindles and such it can be overwhelming so concentrate you efforts on areas that are likely to suffer from abrasion such as handrails, doors, etc.
Generally speaking, all water based finishes will dry relatively flat, and this worsens over time. It’s a good idea therefore to not commit to doing a large area all at once with a finish you’ve not used before. Do a small area first and leave a few days to ensure you’re happy with the result.
I always advise to use the best quality paint that you can afford, especially where the final finish is important. By all means try the Johnston’s aqua range but, if the end-result isn’t impressive, try Dulux Trade Diamond Satinwood which I have found to be the best of the bunch.
One final tip. All paints take a while to fully cure and water-based especially. Although touch-dry relatively quickly it can take a few weeks for the paint to fully harden. For this reason be especially careful in the first few weeks so as to avoid any damage to the paint surface in high-traffic areas.
Nick Hodge – Can I use a water based undercoat paint with a solvent based top coat paint
Darren – Yes you can. The only problem you’ll find, if using a gloss paint, is that it will dry flatter (or less glossy) than if you’d used a traditional undercoat.