There are over 30 grades of redwood, varying in appearance and durability. Redwood can be ordered in standard dimensional lumber sizes. Kiln-dried is more expensive but is more stable, may be helpful for tight jointery like for rail parts. There are two principle grades: Architectural and Garden Grade. Garden grade Redwood should not be used for building decks because it contains sapwood.
– These grades contain only heartwood which exhibits all the best properties of the wood.
Clear Heart – This is a premium grade that offers knot free surfaces. Because of its high expense it is usually only used for rails and trim on decks. Clear Heart grade contains no grading defects. It is normally certified as Kiln-dried.
Select Heart – This is a step below Clear Heart and contains limited knots.
Construction Heart– Con Heart is less expensive than Clear Heart. A limited number of knots and some defects are present.
Deck Heart - Deck Heart has similar appearance and use as Construction Heart but is also graded for strength. Deck Heart is only available in 2x4 and 2x6.
Merchantable Heart – This grade is not recommended for decking. It is the cheapest heartwood grade and allows slightly larger knots than Con-Heart grade and holes limited to the size of knots. You will find checks, some manufacturing flaws, and some splits.
– These grades may contain sapwood and are not recommended for decks. Garden grades are usually used for outdoor furniture, trellises, fences, and planters.
Clear – Clear Garden exhibits the same general characteristics as Clear Heart except that sapwood is present. It is normally certified Kiln-dried. Garden grades should not be used for decks.
Construction Common – Exhibits the same general characteristics as Con-Heart but contains sapwood and heartwood. Garden grades should not be used for decks.