What is the minimum quality of plywood that can be used for a concrete form?

The minimum quality of plywood that can be used for a concrete form is B - B. This grade is specific for applications where strength and resistance to moisture are essential, which is crucial when constructing forms for concrete pouring.

The B - B grade plywood is suitable because it offers a solid surface with good structural integrity, ensuring that it can withstand the pressure exerted by the wet concrete. Additionally, this type of plywood has fewer knots and blemishes than lower grades, contributing to a smoother finish on the concrete surface once poured.

In contrast, while higher grades like A - A may offer superior strength and visual appeal, they are often not necessary for the practical purpose of forming concrete, and using them could be unnecessarily costly. Lower grades such as C - C or D - D would not provide the adequate strength or durability required for formwork, as they may contain voids and defects that could compromise both the form’s integrity and the final finish of the concrete.

Thus, B - B grade plywood strikes the right balance between quality, performance, and cost for concrete forming applications.