simple past tense and past participle of build up

Alternative form of built-up

Made of sections or layers, one on top of the other. / Having increased in size, quantity, or intensity over time; accumulated. / Constructed or enhanced.

(roofing) A continuous, semi-flexible roof membrane, consisting of multiple plies of saturated felts, coated felts, fabrics or mats assembled in place with alternate layers of bitumen, and surfaced with mineral aggregate, bituminous materials, a liquid-applied coating or a granule-surfaced cap sheet.

plural of built-up roof