HISTORIC IRONWORK REPAIRS IN TIMBER-FRAMED BUILDINGS.

Chapter 5

5. Types of Iron Ties. 3/6.

5.6 Cramps.
Traditionally, these are long slender rods with the tips bent at slightly under right-angles and are used as hold-fasts during timber conversion. Their use has been extended to reinforce timber joints by driving them permanently in across the stress path to prevent pulling out. Later the smith adopted the principle in the design of the tie by hammering the ends to a point and turning them in to help with the location of the tie before the nails were driven in (Fig. 5.15 - 5.16).

Fig 5.15. A strap cramped at either end. The cramp has been drawn down, presumably to increase its length and appears to be made of a reused cart tire. This would date it to the 18th century or earlier. The other fixings may provide a closer date.

Fig 5.16. A broken cramp that has been replaced with a stapled L-tie. The uniformity of its form and fixings indicates a 19th century date for the L-tie. The cramp must therefore be earlier.

5.7 Brackets.
Iron ties in the form of brackets are seldom used probably because of the intrinsic weakness of the form. However they are used to secure inserted door posts and the like (Fig.5.17). They are popular in mill buildings where vibration needs to be damped to prevent the joints pulling out (Fig 5.18). L-ties can be turned inside out to form brackets where other repairs may be impractical.

Fig. 5.17. A 20th century mild steel strip bracket originally used to secure a failing door post. The machine drilled and countersunk holes as well as its milled uniform section make it simple to identify.

Fig. 5.18. A nailed in internal bracket on a main tie beam in Lode Mill, Cambridgeshire. The large square headed nut ensures the bracket cannot be torn out. Dated to the mid 1800's.

5.8 U-straps.
A tie in the form of the letter U (Fig 5.19). Distinct from a stirrup in that the terminals only accommodate nails or staples and no mortice is required for fitting. Used to bind posts to wall ties.

Fig 5.19. A U-strap on an arcade post of the Wheat Barn at Cressing Temple. Of uniform section with drilled and countersunk holes and nailed in with round clouts this repair must date to the end of the 19th century or later. It has been repositioned at least once.

5.9 Draw-ties, 5.10 Forelock Bolts, 5.11 T-pins.