1) There are two distinct meanings, and the earliest references are to those buildings in which lead was kept during major construction projects, such as the minsters in Ripon and York.
1354-5 et sculpantis thakbordes pro coopertura domus plumbarić, Ripon
1371 In j ladell empto pro le led hous, 3s 4d, York
1424-5 Item Ricardo Horner circa ledhows ... per xv dies et di. capienti per diem 6d, 7s 9d, Ripon. However, from the sixteenth century ‘lead’ more usually referred to a large vessel made of lead, which could be used in various operations such as dyeing and brewing: 1557 In the lead howse, Thornton Bridge. Most of the evidence suggests that lead-houses in that period belonged to clothiers and were where dyeing took place, as in the inventory of a Leeds clothier called John Pawson: 1576 In the Leadhowse ... one Leade
1584 Thomas Lockwood ... hath encroached of the waste ... and thereupon set a dyeing lead, Almondbury
1591 To my son William my lome & my lead & my tenters, Bramley
1608 John Armitage, clothier ... granted all that lower and southern end of a house at Undrebanckes ... half a lead house, half a fold, Honley
1710 the Bayliff went to the Leade howse dore, went in and found a Leade sett there, Oakenshaw.