To put the matter simply, the two words are in construct—what T.O. Lamdin has called “close juncture:” byt by itself, means “house”; byt in front of dwd, means “the house of [David].” The determined noun, governed by the genitive proper noun, acquires considerable meaning in a construct relationship. This, and the fact that byt could not have stood alone, is the reason the word-divider is missing in the inscription (see Freedman and Geoghegan, “‘House of David’ Is There!” BAR 21:02).