Veranda beams and posts – rusting of brackets/bolts

Cause

Insufficient corrosion protection for the environment

Repair

  • for very minor rusting only, sand off the red rust, apply a zinc-rich primer and a metal primer then apply two finish coats

  • replace severely corroded bolts and brackets

    • Where the beam sits in a rebate beside the top of the post, fix with 2 x M12 bolts and 50 x 50 x 3 mm washers (see drawing). Ideally the bolts should be 60 mm apart, with 100 mm of post above the top bolt to reduce any risk of splitting the timber post. Use stainless steel fixings in coastal environments.

    • Fixing options where the beam sits on top of the post include using M12 bolts on a 6 mm hot-dipped galvanised steel T bracket (useful where there is a butt joint in the beam above the post) or M12 bolts on a 6 mm hot-dipped galvanised steel strap.

Cause

Lack of cleaning and/or coating maintenance on painted non-galvanised brackets

Repair

  • for minor rusting only, sand off the red rust, apply a zinc-rich primer and a metal primer then apply two finish coats. Alternatively, temporarily support the structure and remove the brackets. Replace with 6 mm hot-dipped galvanised brackets and M12 bolts

  • replace severely corroded bolts and brackets as in the repair above

Cause

Erosion of galvanising 

Repair

  • for minor rusting only, sand off the red rust, apply a zinc-rich primer and a metal primer then apply two finish coats

  • replace severely corroded bolts and brackets as in the top repair