Thermally treated wood products are made from several species of wood. One common species used in thermal modification is North American White Ash as this species is very easy to work with when it comes to installing either the decking or siding products. Ash is considered a joinery wood and is used commonly in the woodworking industry such as baseball bat manufacturers. Ash is very forgiving when it comes to working with it but also very durable which makes for a excellent choice of species for many woodworkers. I have worked with Ipe in the past and it can be difficult at best on yourself and the tools you use when working with it so I prefer to stay away from it especially if there is another form of hardwood that is more environmentally friendly and easier to work with.
All hardwoods are susceptible to end split once boards are cut. With thermal modification comes a much more stable and durable wood product but the process of thermal modification makes the wood become very brittle and dry because the moisture in the wood has been removed during the thermal modification process. Its important to seal all end cuts as soon as practicably possible. Leaving the ends of the boards that have been cut without any end sealer will eventually lead to end split and this can make for advanced problems with your decking and siding products should those splits turn into cracks.
We use a product line distributed by DeckWise called Ipe Seal. Its a wax emulsion sealer proven to increase the structural integrity of hardwood decking. Designed to prevent end checking (drying splits) in freshly sawn logs, lumber, turning blanks, and other exposed wood end and face grain. Ipe Seal™ creates a bond that extends the life of each deck board or siding piece. Don’t let your investment in exotic woods or thermally treated lumber be taken away with unsightly end checking and splitting.