Spraying Polyurethane

Spraying Polyurethane: Everything You Need to Know!

When you need to apply polyurethane, you’ll have a variety of applicators to choose from – spraying, brushing, rolling, and even wiping it on.

Spraying polyurethane can be a preferred method of application for numerous reasons, but there are also notable drawbacks you’ll want to be aware of.

In this post, I’ll explore everything you should know about spraying polyurethane including the pros, cons, and how to spray polyurethane. Let’s dig in!

  • Spraying polyurethane is more likely to yield an even coating, and it’s also faster than other methods of application. Plus, it’s ideal for upright wood surfaces and hard-to-reach areas.
  • Spraying polyurethane does require a larger workspace, and it can be more wasteful and expensive if you go overboard when applying it. Lastly, I recommend only spraying water-based polyurethane.

How to Spray Polyurethane

1. Gather Your Materials & Prepare the Workspace

Before you start spraying polyurethane, you’ll need to gather all the materials necessary to make this possible. It’s best to get all your materials together before you start so you don’t have to interrupt the process later on.

The following materials are essential to spray polyurethane:

  • Spray gun or paint sprayer (check out my list of the best sprayers for polyurethane)
  • Water-based polyurethane
  • Drop cloth
  • Easels (2-3)
  • Tarps (2-3)
  • Sandpaper (180-220 grit works best)
  • Mineral spirits (paint thinner)
  • Clean tack cloths (2-3)
  • Vacuum

You’ll also need the following pieces of safety equipment to ensure you’re not in danger when spraying the polyurethane:

  • Goggles
  • Respirator
  • Gloves
  • Overalls
  • Long sleeves

After you have everything, it’s time to prep the workspace.

First, lay the drop cloth down and then set the workpiece on it.

Next, set up 2-3 easels and hang a tarp from each one. Once the tarps are secure, arrange the easels so they form a half-circle barrier behind the workpiece.

This setup will ensure you don’t get polyurethane on anything beyond the formed barrier, so it’s ideal for small workshops that are packed with tools.

Next, open a couple windows and turn on a fan or two; ceiling fans, floor fans, and desk fans work best. This way there’s good ventilation while you’re working.

Even water-based polyurethanes contain toxic volatile organic compounds (VOC), so it’s best to ensure the fumes these polys emit don’t linger.

2. Prepare the Polyurethane for Spraying

Water Based Polyurethane

This is an important step, so pay close attention!

You must stir your water-based poly before it can be loaded in the spray gun. Stirring will mix the solids and flattening agents that naturally sink to the bottom of the can.

After the poly has been thoroughly mixed, consider adding thinner.

In my opinion, thinner isn’t all that necessary when using water-based poly. Still, if you don’t like how thick the poly is, add some water to it.

You COULD use an oil-based poly and thin it with mineral spirits, but I don’t recommend this method—I’ll explain later.

Note: Before thinning polyurethane, read the manufacturer’s recommendations; these are on the back of the can.

3. Test the Sprayer & Poly

HomeRight Finish Max Sprayer
This is the sprayer I use

Once the poly is ready, add some to the sprayer to test it out. Sprayers can be unpredictable, and many will sputter out poly at first because there’s air in the chamber before the poly is added.

But after a few seconds of spraying, the sputtering should stop and a smooth stream of spray should take over.

Testing will also show how the poly looks once applied to a surface. For this reason, it’s best to use the same material as the workpiece (or something similar).

4. Prep the Workpiece

Sand Before Polyurethane

Prepping the workpiece is arguably the most important part of the process. After all, if it isn’t in a receptive condition when you start spraying, the poly won’t adhere well.

First, you need to sand the workpiece with 180-220 grit sandpaper. But I use the word “sand” here only because sandpaper is involved; you’re not really sanding, rather roughing up the surface so the wood’s pores are more exposed.

Refrain from applying too much pressure when sanding, otherwise you’ll take off too much material, leaving an uneven surface.

DON’T use an orbital sander here, as it’ll definitely take off too much material.

Once you’ve roughed up the entire surface, grab your vacuum to suck up any leftover sawdust; it’s best to use a vacuum with a dust-collection bag.

After you’ve vacuumed up everything you could, grab the mineral spirits, pour a small amount on one of your clean tack cloths, and gently go over the wooden surface to remove any caked-on sawdust, dirt, etc.

Note: If you don’t want to use mineral spirits here, you can use warm, soapy water, but I think mineral spirits is much more effective.

Once you’ve given the surface a thorough cleaning, let it dry. You need to give it time to dry completely, otherwise the poly won’t adhere well once you start spraying.

5. Apply the Polyurethane

When spraying polyurethane, the sprayer should be 10-12 inches from the workpiece.

Spray the polyurethane in a sweeping, continuous motion; this way you avoid over-applying in one spot, which often leads to runs and drips, especially on vertical surfaces.

Don’t worry about spraying with or against the wood grain; this is only relevant if you’re brushing or rolling poly on.

Your goal when spraying should be to achieve maximum coverage with a minimal amount of polyurethane; if coats are thin, they’ll dry quicker and they’ll be easier to touch up.

If you’re spraying a piece of furniture, like a table, you need to spray at numerous angles to achieve maximum coverage.

Using a table as an example, you should spray the tabletop first, and then move to the table legs. Once these elements have been sufficiently coated, flip the table over so poly can be applied to the underside.

If your spray pattern is disjointed, this may be evident once the poly dries, so do your best to spray in a continuous motion; keeping your wrist firm as you spray will help.

6. Let the Poly Dry

After you’re done applying the first coat of polyurethane, give it time to dry.

Some water-based polys dry in just 30 minutes.

If you thin water-based polyurethane before applying it, you won’t have to wait as long for it to dry.

Oil-based polyurethane, on the other hand, can take 5-7 hours to dry. But when I use oil-based polyurethanes, I let them dry for at least 24 hours, since working on oil-based poly that isn’t completely dry almost always leads to a big mess.

Again, I don’t recommend using oil-based polyurethane as spraying poly, but if you do choose to go this route, be prepared to wait longer.

Repeat steps 4-6 until you have the desired number of polyurethane coats. Usually, 3-5 coats is enough for water-based polyurethane, but some woodworkers recommend using as many as seven.

Personally, I’ve never needed to apply more than five coats. Water-based poly may not be as durable as oil-based, but it can hold its own (so long as its not subjected to harsh conditions routinely).

Need more help spraying polyurethane? Check out the video below!

Pros of Spraying Polyurethane

Even Coats

No matter what kind of applicator you use, when applying polyurethane your number-one priority should be achieving even coats.

The first coat especially should be even, since this is the coat on which all others will be based. The final coat should be even too, as this is the coat that’ll be visible.

Spray guns are better at achieving even coats because they release a continuous mist of poly that cover a wide area.

And just because you’re spraying water-based poly doesn’t mean you can’t get a thicker base coat; you can, but you need to make sure you avoid over-spraying, as this can be a pain to rectify.


Applying polyurethane with a sprayer is much faster than every other application method.

But just because a sprayer can put on a polyurethane coating quickly doesn’t mean it’s automatically better than other applicators.

In truth, how well the sprayer works for you largely comes down to your skill level and experience. Therefore, novices may struggle at first, but practice makes perfect.

So long as you spray in a fluid, sweeping manner, your spray patterns are likely to achieve maximum coverage in a minimal amount of time.

But don’t prioritize speed over accuracy, otherwise you’ll get blotchy coats that’ll need to be corrected sooner rather than later.

Vertical Surfaces & Hard-To-Reach Areas

Sprayers are great at applying polyurethane to a wide variety of oblong wood surfaces, like doors, tabletops, and desktops.

And when it comes to applying poly to furniture legs, sprayers can provide maximum coverage. That said, you’ll waste a lot of poly this way, so it does come at a cost.

Rollers, brushes, and even rags can’t reach crevices, gaps, and corners like sprayers can.

It’s possible to use a sprayer in conjunction with another applicator, but doing so elongates the overall process, since you’ll need to prep two applicators instead of one.

But before your spray-on polyurethane dries, you need to ensure there are no runs or drips, otherwise you won’t have a smooth finish.

Cons of Spraying Polyurethane

Larger Work Space

If you’re going to use water-based polyurethane spray, you’re going to need a larger workspace, since the sprayer covers a wide area.

Therefore, if you’re confined to a small workspace, it’s best to use brushes or rags instead. You could use a roller, but even these can be inconvenient when space is limited.

And if you don’t set up the easel-tarp barrier correctly, you could get spray polyurethane on your tools.

Sure, you can clear hand tools and accessories out of the workspace before poly is applied, but what about the heavier, stand-alone equipment that weighs hundreds of pounds?

Limited to Just Water-Based Poly

Unfortunately, sprayers are really only good for water-based polyurethane; oil-based polyurethane is generally too thick, and often it clogs sprayers (even after it’s been thinned).

But there are times when oil-based polyurethane is the best poly to go with, like when you need to apply poly to an exterior wood surface.

In these cases, it’s best to apply poly with a roller or brushes instead.

Gel polyurethane, which isn’t used as much as water-based and oil-based polys, also won’t work with a sprayer, since it’s more viscous.

In short, relying on water-based polyurethane spray isn’t a problem in itself. But if you’re looking for thicker coats, ditch the water-based poly and sprayer for an oil-based poly and roller.

More Wasteful

If you’re not careful when you spray polyurethane, you may over-spray, which can be both wasteful and expensive.

High-quality water-based polyurethanes, which I highly recommend, aren’t cheap, and therefore you shouldn’t be careless when using a sprayer.

If you need to make the most of every drop of the polyurethane you have, I recommend using a sprayer ONLY for the broad, wide surfaces; the hard-to-reach places will have to be coated with a rag instead.

I’ve said numerous times that paint sprayers are great at getting poly in crevices, gaps, and corners, but the trade-off is a lot of wasted poly.

Is It Best to Spray Polyurethane?

Some say yes, others say no. Personally, I like spraying polyurethane, but there are times when a sprayer should be swapped out for a better applicator.

For example, if you need to apply polyurethane to a floor, a roller is best. Sure, you could use a sprayer, but it’d be awkward at certain points, and you’d really have to do some high-level covering to protect the baseboards, walls, and trim.

My favorite poly application method is wipe-on or applying polyurethane with a rag, since you get the most control. That said, it takes much longer, and it’s hard to do successfully if you’re not familiar with this method.

Spraying vs Brushing Polyurethane

Applying Poly with Brush


When it comes to achieving an overall smooth polyurethane surface, the sprayer has the brush beat.

After all, when you spray polyurethane, there’s no worrying about brush marks.

Plus, a sprayer is great at putting down thin layers, which will be easy to smooth out later with a clean tack cloth.

That said, a sprayer can apply too much polyurethane if you’re not careful, resulting in an uneven and potentially pocked surface.

Ease of Application

As far as ease of application is concerned, a brush is much easier to use if you’ve never applied polyurethane before.

I definitely discourage using a sprayer if you’re not familiar with how water-based polyurethane works; you may waste a lot of poly or even ruin the workpiece if you don’t know what you’re doing.

Polys Available

Brushes can apply water-based, gel-based, and oil-based polyurethanes, whereas sprayers work best with water-based polys.

That said, you can use oil-based and gel-based polys with a sprayer, but you may run into issues like clogging, inadequately mixed poly, blotchy surfaces, and limited spray capacity.

Waste & Cost

Both applicators can be wasteful and expensive if you don’t know what you’re doing.

With a brush, you run the risk of applying a thicker coat that doesn’t dry completely, and this will have to be touched up later if you want to achieve a 100% smooth and even coating.

A sprayer can be even more wasteful. But if you know how to use this tool and you spray in the best possible conditions, this applicator then becomes the most cost-effective option.

Spraying vs Rolling Polyurethane

Rolling Polyurethane


Rollers are great at putting smooth poly coats on floors and other large, flat surfaces, but they’re much less useful when you have to coat furniture that has multiple corners, notches, ridges, etc.

Overall, I’d say these two applicators are about even in terms of capacity to put down smooth coats.

That said, just like with brushes, you have to be aware of roller marks when applying either water-based or oil-based polyurethane.

Ease of Application

A roller is much easier to use; all you have to do is push and pull. But in all honesty, rolling out poly is far from that simple. In fact, you need to roll in specific patterns at certain times to achieve a poly coating that’s smooth and even through and through.

Polys Available

Rollers can put down oil-based, gel-based, and water-based polyurethane. They work best with thicker polys, since you can apply more pressure with a roller to achieve thin polyurethane.

Waste & Cost

Rollers can waste just as much poly as sprayers, if not more. This is because their naps often absorb more poly than is needed. To avoid this problem, don’t dip the roller in poly. Instead, carefully pour some poly on one section of the nap; it’ll disperse well once you start rolling. 

Tips for Spraying Polyurethane

Watch for Runs & Drips

Runs and drips are often the result of over spraying, and they can be avoided if you apply thin coats only.

These can also form if you’re using incorrect spray patterns. Remember, it’s best to spray in a continuous, sweeping motion, this way no area ever gets over-saturated with poly.

Runs and drips are much more likely when spraying upright surfaces, but they can occur on flat surfaces too.

In a way, runs and drips are to sprayers what brush marks are to brushes, which goes to show no poly application method is a piece of cake.

Only Spray in a Well-Lit Room or Outside

You should only spray polyurethane in a well-lit room, otherwise you won’t be able to clearly see what you’re doing.

If your workshop doesn’t have sufficient lighting, you can work outside—or in your garage (with the garage door open)—but I’m not a fan of this method.

Yes, you can use the drop cloth, tarp, and easel setup I discussed earlier, but outside you’ll be at the mercy of the wind.

And the wind blowing the polyurethane all over the place isn’t the only thing you’ll have to worry about; it could also blow leaves, dirt, and other debris on your drying poly.

So even if it means you have to buy a floor lamp or two, you should apply poly indoors, this way unnecessary hassles are avoided.

Safety Gear Is Essential

When applying polyurethane with a sprayer, you need to be wearing proper safety gear, otherwise you may be over-exposed to the toxic fumes polyurethane emits.

Even though water-based poly, the best polyurethane for spraying, contains far less volatile organic compounds (VOC) than its oil-based counterpart, you still need to wear safety gear.

After all, without goggles or a respirator, the polyurethane spray could kick back and hit you right in the eyes, nose, and mouth, landing you in the ER for a few hours.

Only Use Water-Based Polys

I’ve said numerous times already that I don’t use oil-based polyurethanes for spraying, and here’s why:

For one, you have to thin these, and adding thinner can be difficult. And why add a difficult step when you can just use water-based poly and avoid thinning altogether?

Even if you do thin polyurethane successfully, you may not get the desired result from your sprayer.

Specifically, the viscousness of the oil-based poly—even after being thinned—may be too much for the sprayer to handle, in which case its spraying capacity would be severely hampered.

Moreover, the oil-based polyurethane that does come out may be rife with bubbles, and these would have to be knocked down with a craft stick or something similar.

Don’t Over-Spray

There are a few reasons why you should avoid over-spraying polyurethane.

For one, removing excess poly from wood can be a pain.

If you remove too much, you’ll have to reapply, but you may not be able to do this immediately because the wood may not be receptive—it’ll need time to dry, and you may even need to go over the spot with mineral spirits, sand, etc. before more poly can be applied.

Also, over-spraying creates runs and drips, and if these aren’t caught they’ll dry in place and you’ll need to remove them later. Again, this can be a pain, as it’ll at the very least elongate the overall poly application process.


Can you spray polyurethane?

Yes, you can spray polyurethane. This is one of the most preferred ways to apply polyurethane, since it’s easier to apply even coats, faster, and easier to coat vertical surfaces and hard-to-reach areas. But you’ll need to be somewhat skilled with a sprayer to achieve a smooth finish.

Does polyurethane need to be thinned before spraying?

It depends on which polyurethane you’re using. If you’re using a water-based poly, you don’t need to thin beforehand; that said, many woodworkers still do this so the poly dries quicker. If you’re using an oil-based polyurethane, thinning with mineral spirits beforehand is absolutely necessary.

Final Thoughts

In the end, spraying polyurethane is a preferred method of application because:

  • It’s easier to achieve thin, even coats with a sprayer.
  • It’s a faster process overall since spray-on poly dries quicker.
  • It’s easier to coat vertical surfaces and hard-to-reach places, which can’t be said of rollers or brushes.

But you need to be careful when spraying polyurethane coats on a surface, since it’s much easier to over-spray and you can harm yourself if you’re not wearing proper protective gear.