The safe roof: installation of rafter purlin anchors

A roof, regardless of whether it is a house or a terrace, should be stable, because nobody wants it to fall on the residents' heads. In the past, mortise and tenon joints were used, today rafter purlin anchors are used for fastening.

Rafter purlin anchors in the roof structure

The rafter purlin anchor connects two wooden surfaces running at right angles to each other. It is a 90 ° metal angle, the wings of which are shifted lengthways. So it does not connect two directly adjoining, but in height offset surfaces. The most typical installation situation is the purlin roof, but the rafter purlin anchors can also be used for other slightly sloping roofs, wherever rafters meet a supporting beam.

  • Also read - The correct application of rafter purlin anchors
  • Also read - rafters - the common dimensions
  • Also read - How to calculate rafters?

If the roof overhangs, the rafter anchor can be installed on the outside and inside of the roof. Whether rafter purlin anchors are required on both sides depends on the expected load. If the purlin and rafters are flush with the outside, it is only installed on the inside. Where the rafter rests on the purlin, a piece is removed so that a larger contact surface is created and the rafter purlin anchor is not loaded with weight, because it is supposed to secure the position of the rafters and absorb tensile forces.

Installation of the rafter purlin anchors

The assembly of rafter purlin anchors is relatively straightforward. It is only important that the dimensions of the rafters and rafter purlin anchors match. For this reason, rafter purlin anchors are offered in different sizes. The rafter purlin anchors should not protrude beyond the rafters, but they shouldn't be too small either. You need for the assembly:

  • the corresponding number of rafter purlin anchors in the appropriate size
  • Special nails. Anchor or comb nails, corrosion-protected, diameter 4.0 mm, length 40 mm)
  • a hammer

After the rafter is in the desired position, nail the rafter purlin anchor to the side of the rafter and to the purlin. Position the rafter purlin anchor so that the nails have as much distance as possible from the wood edge so that they are held in place by sufficiently thick material. You need at least two nails for each surface of the rafter purlin anchor, more is better. The amount is calculated using a table combined with the expected load.