Is It OK To Burn Untreated Lumber?

Throughout the years I’ve accumulated god knows how many pieces of construction scraps. All those random scraps of 2x4s and 2x6s have been sitting in my wood shop for over a decade. I use the odd piece here and there, but they were starting to get out of control. After saving them for the better half of a decade I needed to find some use for them. So I asked myself a simple question; Can I burn untreated lumber in the fireplace?

Yes it’s safe to burn untreated lumber in both indoor and outdoor fires. Most 2x4s are made out of soft woods like pine and will be perfectly safe to burn. Make sure you give the boards enough time to dry, because softwoods tend to have a high moisture content. It’s best not to burn painted, stained, and pressure treated wood, because they can release toxins into the air.

How do I know whether or not the board is safe and ready to burn. I’ll go over those questions and more in the rest of this article.

Burning Untreated Lumber Is Safe

There’s no problem at all with burning dry lumber as long as it’s not pressure treated. I burn scrap pieces of wood all the time in my fireplace. Sometimes I’ll keep the big stuff, but there’s really nothing you can do with smaller boards. Burning them is better than paying to toss them in the trash(maybe not for the environment).

The only concern I’ve heard about burning untreated wood is that the ends are sometimes painted to control the drying process. Burning paint isn’t the best thing for your health, but such a small amount of paint shouldn’t be a problem.

Plywood and OSB are safe to burn outside, but you don’t want to bring scraps into an indoor fire. I’m not talking about a dangerous chemical problem in the wood. They just burn ridiculously hot and can cause serious damage to your fireplace or wood stove. There’s something about how thin and dry the boards are that goes up fast.

Some people claim the glue that keeps the layers together is toxic, but there’s really no proof of that. Plus if you’re only burning the wood outside you won’t be breathing much of it in anyway. You’ll have to make your best judgement and figure out the risk/reward that you’re willing to accept. Personally, I’ve breathed in worse fumes than glue in my life and I’m not about to take an unnecessary trip to the landfill.

Don’t Overload Your Fireplace

Whether or not your lumber is wet or dry depends on the source and how long you’ve been storing it. Generally speaking, dimensional lumber is often quite dry. That’s great for starting fires, but you can overload your fireplace if you’re not careful.

Overloading the fireplace doesn’t sound like that big of a deal, but it can really over-fire a stove. You don’t want to cause damage just because you’re trying to burn some untreated lumber.

You Still Have To Season The Wood

How have you been storing the lumber. Dimensional lumber usually comes with a low moisture content, but softwoods are notorious for soaking in water. You could run into moisture problems if you don’t properly stack and cover the wood.

I recommend following the same general guidelines as with regular firewood. Keep the wood up off the ground on a rock, cover it up to keep it dry, leave the sides exposed to improve airflow, and try to give the wood as much sunlight as possible. If you follow all those steps your lumber should be ready to burn at any time.

Don’t Burn Painted and Stained Wood

It might be tempting to burn all the wood you can get your hands on, but think twice about burning painted/stained wood. There’s no way to know what kind of chemicals are included in the paint and stain formulas. They may be safe to burn or you could be breathing in dangerous chemicals.

The manufacturer sure as heck, isn’t about to recommend burning their product so there’s no way to get a clear answer. If you choose to burn painted or stained wood make sure it’s in an outdoor firepit.

Don’t Burn Pressure Treated Lumber

Most people know that it’s a bad idea to burn pressure treated lumber, but I figured that I need to mention it anyway. Pressure treated wood contains lots of preservatives, fungicides, and insecticides. It’s great for preventing rot and insect damage, but breathing in the fumes would be terrible for your lungs.

When you burn pressure treated wood it releases an ungodly amount of toxic chemicals into the air. It’s best to repurpose pressure treated lumber or get rid of it in a landfill. You can’t even set the boards back in the woods, because they won’t rot.

Wood Pallets Have Chemicals Too

If I was going to guess, I’d say 90% of the bonfires I went to in high school consisted of burning wood pallets. Knowing what I know now, I probably wouldn’t have done much different, but it’s always fine to second guess yourself. Maybe I’d stand a few feet farther away so I wouldn’t have been breathing in all that toxic smoke, but I wouldn’t give those beer filled memories up for anything.

Nowadays there are loads of crafty things you can do with pallets. Put them up on Craigslist or Facebook Marketplace and I’m sure somebody will come grab them up. Or you might want to make a nice table, chair, and all kinds of other things.