How Long Between Coats of Plaster?

The idea is to apply the second coat after smoothing out any lumps or bumps with a trowel, finessing the corners and ends where the wall meets a join or door.

It depends on the surface you are plastering - but it's impossible to smooth over inconsistencies in the surface once your first plaster layer has completely dried through.

Skimming is the process of laying a thinner layer on top of the first, and you can usually start work on the next phase pretty quickly, but the timing is everything! Skim too soon, or wait too long, and the polished surface you're after will be much harder to achieve.

Factors That Influence How Long You Should Wait Between Plaster Coats

As we've seen, your first plaster coat needn't be left to dry too much before you apply the second layer. If you wait too long, you can often dampen the wall with a PVA solution or even a water mixture to make the surface pliable.

Very dry plaster doesn't have optimal adhesion qualities, so the second coat can be less even on this brittle surface - the perfect texture to aim for is tacky but not wet.

There is an easy way to check whether the plaster has reached that ideal putty consistency:

• If you push your fingers into the plaster, you should be able to make an indent, BUT
• The plaster shouldn't come away on your fingers.

Remember that plaster doesn't dry evenly, depending on the thickest areas and coldest parts of the wall, so it's best to check a few places to see where you are up to in the drying process.

Lots of things will impact the speed of your plaster drying, including:

• The thickness of the first plaster coat.
• The surface material you're applying it onto.
• How warm or cool the wall is.
• The room temperature and airflow.

If you're in a hurry, opening windows to boost ventilation or even using a heater can speed up the drying time, but you can start work relatively quickly with just a little patience.

Other Considerations for Achieving a Perfect Plaster Finish

Often, the first plaster coat does become too firm. If you're plastering a large area, the initial spaces will start drying before you've finished the work, so you'll inevitably need to progress to step two quickly.

If that happens, you can opt for a slightly thicker second coat. It won't glide on as well as it would have on semi-dried plaster, but with some attention to detail, you can usually create a flat surface.

The first coat of plaster acts like the base for the second, so the objective is simply for the application to be a flat foundation.

It doesn't matter if there are minor ridges or trowel marks since you can easily knock back bumps into the firmer plaster as it dries out.

However, a caveat exists if you're skimming onto plasterboard. In this scenario, you have a flat, uniform surface and will often find that the smoothness of the first coat will be essential to achieving a perfectly even appearance.

Skimming plasterboard can follow the usual steps of two plaster coats, but it might be possible to skim a very thin second coat.

If you can't get an even second coat, a further option is to go for a third layer, using thin plaster coating to trowel a consistent finish.

It's also worth looking at the type of plasterwork you're undertaking - re-skim and backing coats applied over old plaster can experience high suction rates. The old dry plaster absorbs the water from the application so quickly that it's challenging to start your second coat in time.

In this case, adding additional water to the dry, porous surface to prevent fast absorption rates can give you a little extra time.

We'll talk more about PVA shortly, but, in these scenarios, it can be useful to control the suction on a pre-existing wall. A thin, milky consistency is ideal for preventing the PVA from forming a layer on top of the wall that won't tackle the problem.