Summary:
Features include 1) resupinate growth on horizontal timber, or sometimes bracket-like on vertical wood surfaces, mostly often indoors, 2) a cap surface when present that is silvery-white to gray (discoloring red-brownish when bruised), thick, lubricous-tomentose, and tuberculate-inflated, with a blunt white-tomentose margin, 3) a spore-bearing surface that is merulioid, and olive-yellow to brownish yellow or orange-brown or cinnamon, with a whitish-tomentose marginal zone and whitish to grayish rhizomorphs, 4) a spore print that is orange-brown to orange-yellow to brownish, 5) spores that are elliptic, smooth, and yellow, 6) smooth, fusiform cystidioles, and 7) a dimitic hyphal system, the hyphae with clamp connections. Serpula lacrimans is one of the principal dry rot fungi: the fungus can, according to Breitenbach(2), produce its own moisture after the initial stages of growth (and can therefore attack dry wood).

Microscopic:
SPORES 8-12.5 x 4-6 microns, elliptic, smooth, thick-walled, spore print "orange-brown to orange-yellow to brownish", (Arora), SPORES 11-13(14) x 5.5-8 microns, elliptic, smooth, yellow, some with droplets; BASIDIA 4-spored, 45-70 x 6-10 microns, narrowly clavate, with basal clamp connection; CYSTIDIOLES between the basidia, 50-80 x 5.5-8 microns, "fusiform, some sinuous, smooth"; HYPHAE dimitic; generative hyphae 2.5-6 microns wide, colorless, with clamp connections; skeletal hyphae in basal layer and rhizomorphs 2-7 microns wide, brownish, thick-walled, some encrusted with crystals, (Breitenbach), SPORES has cyanophilic inner wall (Lincoff), skeletal hyphae cyanophilic (Ginns(23))

Notes:
Serpula lacrimans has been found in BC, WA, OR, ID, AB, MB, NS, ON, PQ, SK, AK, AL, AZ, CA, CO, CT, DC, FL, GA, IA, IL, KS, KY, LA, MA, MD, ME, MI, MO, MT, NC, NE, NH, NJ, NM, NV, NY, PA, SC, UT, VA, VT, WV, and WY, (Ginns(5)). It has also been found in Europe including Switzerland, and in Asia, (Breitenbach).