Hips

What is the purpose of Dry Hip Support Trays?

Dry Hip Support Trays are designed to span underneath the center of one hip tile to the next to ensure that the hip tiles are kept as straight and at the same angle as possible and the joints between hip tiles are kept as far from the joints in the support trays as possible. To assist the roofing contractor a 'V' shape marking showing where to cut the first unit at the eaves is provided. The remainder will then fall into place automatically.

 

When should hip irons be used?

Hip irons are normally made from 6mm thick galvanised steel, 25mm wide and 300mm long bent into the shape of a hook with a scrolled end. They are screwed to the top of the hip rafter at the eaves. The curled end should stand upright beyond the fascia board to line up with the eaves overhang of the roof tiles.
Hip irons are traditionally used with mortar bedded Third Round, Plain Angle or Universal Angle Hip tiles. Their function is to prevent the lowest hip tile sliding off the roof particularly whilst the mortar is wet or if the mortar has failed due to hairline cracks. However, with the modern requirement that all hip tiles are mechanically fixed the use of hip irons can be argued nowadays to be more for aesthetic rather than structural reasons. Hip Irons are not used with Bonnet Hips, Arris Hips, mitred hips or Dry Hip. With the latter a Block-End Hip tile is screwed directly to the hip rafter.

 

What is the plan angle of a building?

A plan angle is the angle of intersection between the eaves of one slope and the eaves of the adjacent slope when viewed on plan. The most common plan angle is 90º since most buildings have square corners. However some buildings have walls that do not meet at 90º such as where a wall follows the line of a boundary, which is not parallel with the orientation of the building or bay windows that are formed in a series of facets to produce a panoramic view. A pyramid roof is one that has hips meeting at a point. A pyramid with four equal sides has a plan angle of 90º. With six equal sides the plan angle is 120º and with eight equal sides the plan angle is 135º.