Green’s Dictionary of Slang

1. (UK Und.) to dress up in one’s best clothes in order to present a respectable, if fraudulent, image; thus ext. into non-Und. use; thus built up adj.

1903		Bulletin (Sydney) 9 July 13/2: The frivolous female can be built up cheaply these times. ‘Kiss-curls,’ for a year or so past the trickiest part of many a dear thing’s get-up, are three a shilling.
1906		A. Adams ‘In the Hands of His Friends’ in Cattle Brands 🌐 Watch me build to the one inside with the black eyes. [...] As soon as we get this beef hung up I’m going in and sidle up to her.
a.1909		press cutting in J. Ware Passing Eng. of the Victorian Era 54/1: Jennings agreed to ‘build up’ Archer with clothes, and at another meeting brought him a coat in order that he might appear respectable when he visited his old fellow-servants at the Lodge.

2. (drugs) to roll a cannabis cigarette.

1997		N. Barlay Curvy Lovebox 186: Makin’ calls. Billin’ up. Soundin’ off.
1999		K. Sampson Powder 20: [He] started to build up with the bumper-sized patchouli skins.
1999		(con. 1979–80) A. Wheatle Brixton Rock (2004) 84: Give me a Rizla so I can build up.