When choosing a material for one-time concrete formwork, wood is the best option – boards are cheaper than moisture-resistant plywood, aluminum, or plastic, but they are not inferior to them in strength and quality of support. Also, their advantages include lightness, the possibility of use in further stages of construction, ease of processing, and fastening. Maximum requirements are put forward to the elements holding the foundation.
Taking into account the one-time use, there is no need to use expensive hardwood species, many of them do not have the necessary characteristics. Birch boards do not withstand the expansion of concrete during hydration and crack, oak boards affect the alkaline balance of the mixture. Conifers are optimal in terms of price, moisture resistance, and strength; pine and spruce lumber are bought when building the foundations and walls of private houses and small buildings. Aspen and cheap hardwood varieties are used for massive systems; they do not sag under the weight of a heavy solution.
When buying, attention is paid to porosity: the smaller it is, the better. It is recommended to carry out a visual inspection – with a high percentage of cuts with curved edges, chips, or cracks, the risk of mortar leakage or deflection of the support boards increases.