There is no question that the primary use for Ipe is as a decking material. As a decking product, Ipe is surfaced on 4 sides (S4S) and eased on 4 edges (E4E) which prevents splintering and sharp edges in this very, very hard wood. Depending on how our clients choose to install the Ipe decking, we may have to rout a groove for clip fasteners, but at most, that is all we are doing to the wood before shipment.
As a decking material, Ipe is air dried to around 18% moisture content, before it is milled in South America into deck boards. As an exterior product, this is exactly what you want for a stable decking board. Sun, rain, wild temperature swings, etc. are very hard on a board, and using a gently dried, higher moisture content piece is the only way to weather these conditions.
While we do carry rough sawn and kiln dried Ipe lumber, we don’t get much demand for it. This is a wholly different product that is meant for interior use. It is kiln dried to 6-8% moisture content, and we either sell it as rough sawn, or we will mill is onsite at our own millworks. These are the same species yet involve dramatically different treatment and uses. One will not work in the other’s environment.
With that said, did you know that we also carry kiln dried Ipe decking? That’s a bit of a joke because kiln dried Ipe and air dried Ipe are the same product. So this makes your decision easy as “either” product is the best solution for a deck in a dry climate.
Y’see in an earlier time when the world moved at a slower pace, all woods were air dried. Today, production waits for no man and the seasoning process for lumber has to be faster. So even exterior use decking products get put into a kiln for drying. The key here is that the Ipe is NOT dried to the typical 6-8% moisture content of interior use lumber, but rather is kiln dried to 10-18%. This is just enough to get rid of the free water without banishing the bound water and hardening the cell walls of the wood and therefore making it more brittle and resistant to change.
A board that is resistant to change might sound like a good idea, but it is a recipe for catastrophe. You cannot fight moisture change in an exterior environment. Especially a deck which is probably the harshest environment around for wood. The best thing is a board that is flexible and will go with the flow when it rains and the moisture skyrockets or when the sun beats down all day baking the wood dry.
The question you should be asking is not whether to buy kiln dried or air dried (same thing) but how do I install this decking to deal with the specific environmental challenges present on my deck.
A major thing to consider is how much sunlight your deck will get. Direct sun throughout the day can significantly heat up a deck, forcing out moisture very quickly and causing warping. You stack the cards in your favor by laying down a drier board in the first place, paying close attention to ventilation, and gap spacing. But how do you lay down a drier board if these two supposedly different products are the same moisture content? Answer, give it some time on your job site. Let the boards acclimate. If your deck is going down in the desert in the middle of the summer, the weather will naturally drop the moisture content of the decking to the equilibrium point. Once at equilibrium with the surrounding environment the decking will pick up and dump moisture with the change in seasons and rain and sun. This is where selecting gap spacing and paying attention to even air flow will help you much more than a lower moisture content.
This is why the term “air dried decking” is the most common, because it is widely known that the higher moisture content is closest to the equilibrium point for most of the country. But for those of you in the dry climates or with unshaded southern exposure decks, you will hear that installing “kiln dried decking” is the better solution. I cannot say this enough,
THEY ARE THE SAME THING
I think only we the lumber industry are to blame for this misconception. Like I said above kiln dried lumber is usually 6-8% moisture content and as I said, we do actually carry rough sawn Ipe at that level. As a way to differentiate between this 6-8% Ipe and the wetter decking product we naturally started calling the decking air dried. So let me apologize on behalf of the entire lumber industry for confusing the issue with our crazy terms. This won’t be the last time a lumber term confuses and frustrates you. That I can promise you.
J. Gibson McIlvain carries a very large quantity of Ipe in all sizes from decking boards to joists, balusters, and posts. We also carry both air dried and kiln dried Ipe decking. Had enough of that joke yet?
The next time you encounter a project where the decking material is going to be stressed by an “extreme” environment, ask for kiln dried decking…then ask your dealer what the moisture content is on the boards you will be getting. I guarantee that as long as you are buying decking, both the “kiln dried” and “air dried” will be in the same range.