Why do deck boards split or check?
Exposed wood is like a sponge, soaking up moisture and releasing it with changes in humidity. The fluctuation in temperatures causes the wood to expand and contract, which creates tension between the cracks. This tension can cause the wood to cup, up heave, and even crack (break). For this reason it is recommended that a penetrating wood sealer be applied to all outdoor weather exposed wood especially when in contact with areas that have extreme dry and wet weather.
