Q&A from the Bais HaVaad Halacha Hotline

Above Board

October 9, 2025

Q Are lumber (e.g., two-by-fours) and engineered wood (e.g., plywood or particle board) valid for sechach?

A Most of these products (not the plywood; see below) certainly meet the deOreisa requirement for sechach, as they are gidulei karka (grown from the ground) and not susceptible to tumah. But Chazal (Mishnah, Sukkah 14a) enacted gzeiras tikrah, prohibiting cuts of wood that are more than four tfachim (about 14 inches) wide and long, because a roof built with them resembles that of a house (O.C. 629:18). Two-by-fours, which are smaller, are kosher, even if sanded smooth (O.C. ibid.).

Still, the Shulchan Aruch (ibid.) says that the minhag is not to use sanded wood. The Mishnah Brurah (ibid. 49) offers two reasons: a) Because sanded pieces can be fitted tightly together, they may form a sealed roof, and a roof that is impermeable to rain is akin to a house roof and pasul mideOreisa. b) Even pieces smaller than four tfachim are commonly used in roof construction today, so gzeiras tikrah applies to them, too.

The minhag cited by the Shulchan Aruch only applies to pieces at least one tefach wide (Piskei Teshuvos ibid. 15), so a two-by-two is kosher lechat’chilah.

The use of plywood and particle board is debated among contemporary poskim, as the glue is made of materials unfit for sechach, so these should be avoided (see discussion in Piskei Teshuvos ibid. 16).

Many people use rough wood slats, even those sold in fixed sizes (see list of poskim in Piskei Teshuvos ibid. n. 72). The justification for this is that the Mishnah Brurah’s concerns don’t apply: These slats cannot form a watertight seal due to their rough surface, and they are not typically used in roofs.

In a she’as hadchak (difficult circumstance), where regular sechach is unavailable, one may use sawn-and-sanded wood, even larger than four tfachim (Mishnah Brurah ibid. 50), and even make a leisheiv basukkah (ibid.).