How To Avoid Costly Outdoor Wood Boiler Roof Damage

How To Avoid Costly Outdoor Wood Boiler Roof Damage

Your outdoor furnace MUST burn several hours each day in a COMPLETELY DRY mode. How is that achieved?

Do NOT FORGET this very important operational tip:

Our article from this week will also solve other problems. If you have too much creosote or roof stains, you may be operating your furnace incorrectly. 

Roof stains are caused by moisture in your outdoor wood burner condensing on the chimney cap and dripping on your roof. Moisture is unavoidable in some cases - the air burned in your boiler has some moisture in it, and even seasoned firewood contains 20% moisture.

But there are some steps you can take to avoid COSTLY DAMAGE to your roof. A new roof costs over $1,000 if you include the cost of shipping!

Two of these steps you can take during the summer, and the other step is while you operate your outdoor wood furnace.

Here are the 3 Steps To Avoid Costly Roof Damage:

1. If your roof is showing signs of wear, rust, or corrosion of any sort, lightly sand it every Spring and apply a coat of rust-inhibiting black paint.

2. Follow the recommended steps for properly seasoning your firewood. Those steps are found in this article HERE. Remember: Split, Stack, and Cover.

3. During the burning season, follow the "Dry Burn Procedure". You can read more about that HERE, and I will expound on it more below. 

All furnaces must be dried out every day. Why? Because wood fuel is very high in moisture. Even the most well-seasoned wood contains about 20%moisture and that is a lot of water.

This moisture will create creosote; it will also drip off your chimney cap and stain your roof.

What should happen to the moisture in your wood? We want it to burn off and exit your furnace harmlessly in the form of steam. But that steam coats your entire furnace walls, tubes, door seals, chimney, and your ash with MOISTURE! Even if you burn your furnace perfectly every day, you will still produce a LOT of steam that puts a layer of moisture on your entire boiler.

This is bad. Moisture is bad for steel. Trust us on this - we won't bore you with the technical reasons, but moisture is just bad for steel. Not to mention the fact that this moisture creates nasty creosote.

So, how can I get my furnace to dry out? The answer is simple! Your furnace MUST burn at least several hours each day with only hot dry coals in it.


Yep, the moisture in wood is burning OUT of the wood during MOST of the burn process. It is ONLY after the wood is burned down to black coals when there is no more moisture left in the wood and it can then burn in a very DRY state.


Every day, you must allow your wood to burn down COMPLETELY to a bed of coals. ONLY THEN CAN YOUR FURNACE DRY OUT!  

So what most people do is they only put enough wood in their furnace so that it will be completely burned down to ashes and only a few coals when they refill.

What is the worst thing to do? 

That is a good question!

NEVER "Top Off" your furnace with wood fuel. If you go out to check on your furnace, and it is still half full of wood, DO NOT "Top It Off" with's why:

When you first fill your outdoor wood burning boiler with wood fuel, the water in the wood will start to boil off. When your wood is only half-burned, THERE IS STILL a lot of moisture in the wood. If you then add more fresh wood (full of moisture), your furnace NEVER has a chance to dry out.

If you always do this, then your furnace walls, tubes, door, and seals will continually be coated with steam, and never have a chance to dry out.

Again, the solution is simple: Please only put enough wood in your furnace so that it will be completely burned down to ashes and only a few coals when you refill.   

If you follow these three simple steps, you will keep your outdoor boiler roof in perfect condition - remember, our goal is to Help You heat your home and Stay Toasty Warm and Comfortable for Decades!

For more outdoor wood boiler questions and information on keeping the high efficiency of your heating system, visit our website You can also browse for more Outdoor Wood Furnace Parts.