Thermal movement:

Expansion and contraction caused by temperature changes in a material.

Tie beam:

The horizontal beam across the base of a roof truss, fixed to the lower ends of the main, or principal rafters.

Tile nibs:

Small projections on the underside of roof tiles which hold them in place on timber laths or battens.

Tongued & grooved boarding:

Traditional floor boards.

Torching:

Cement or lime based mortar applied to the underside of tiles or slates in an older roof.

Transom:

A horizontal member of a frame dividing two windows.

Treads and risers:

The horizontal and vertical sections of a staircase respectively.

Trimmer:

A timber beam fixed across the ends of trimmed floor joists to accommodate an opening such as a stairwell, or around a projecting structure such as a chimney breast.

Trussed rafters:

Modern, purpose designed lightweight roof trusses located at regular intervals across the roof, usually pre-fabricated in a factory.