From "A History of Sutton A.D. 675 - 1960" by Robert Smith.

A translation of the Cartulary of Chertsey Abbey published by the Surrey Records Society contains many references, dating from A.D. 1339, to tenants in Sutton and the terms of their tenure....

..An entry in 1343 is suggestive. 'Admission of Oslacus Clericus, to a tenement called Strechereslond, to build a house within three years the lord finding for the house 12 timbers, each 16 feet long. Fine 6d. rent 6d per annum.'

The Abbot of Chertsey at the time of Oslacus was John de Rutherwyk who was unwearied in improving and extending the Abbey estates, in draining marshes, erecting mills and stone bridges, inclosing lands, sowing acorns, repairing chapels and farmhouses, sinking wells, building barns etc. The Abbeys property was very extensive, and near Sutton was Coulesdon, Ewell, and Carshalton.
There is a dedication stone built into the chancel wall at Great Bookham. A similar dedication stone, with the date 1327, at Egham, which preserves the record of the rebuilding of the chancel of that church by John de Rutherwyk, traces of whose work were visible also in Sutton and Epsom Churches, prior to their 19th-century re-construction.
Source: 'Parishes: Horley', A History of the County of Surrey: Volume 3 (1911), pp. 200-208.

Why did the Abbot of Chertsey, the lord of Sutton give the timber for a house unless it was for a Rectory? Was Oslacus the Clerk the priest of Sutton at the time?

If John de Rutherwyck did cause work to be carried out on Sutton Church then it may have been done over several years as building with stone requires time for the mortar made of lime to dry, shrink and settle, a process that can take six months or more. The financing of the work would have been another question. It would have come from the income from the manor, with the Abbot spending money when it was available and just delaying work when the harvest and tithe income was bad.