Flat Roof Eaves Construction Details

The design of your eave is dictated by the construction of your roof.

Flat roof eaves construction details.

The wallplate is secured to the internal wall separated by dpc. Fix a rafter spacer tray to provide a clear air path between underlay and insulation. Trusses streamline construction but it s important when using them to make sure the resulting eave works with the design of your building. If a sprocketted or bell cast detail is used then eaves courses should beno lower than the minimum recommended roof pitch.

The construction of the flat roof is similar to that of the timber upper floor. The main component of any eaves detail is the rafter tail the part of the rafter that extends beyond the exterior wall. To determine exactly what the rafter tail will look like i always make a full size drawing on a scrap of plywood of all the eaves elements including framing and finish materials see illustration above. Additional construction details drawings.

On larger roofs it s probably cheaper to use tapered foam insulation on top of the roof sheathing. Trada and approved document part a give guidance on sizes of joists for flat roofs relating to spans and loading. Joists are placed on edge spaced at 400 600mm centres supported by external and internal load bearing walls. The wallplate is then used to secure the rafter to.

This modest slope can be achieved in a number of ways. From there the flat roof system you choose will determine the materials you apply. Before manufactured trusses the simplest roof construction involved extending exposed rafter tails beyond the walls of the house. With a cant strip or raised fascia a beveled wood or foam antiponding strip is required to prevent ponding of water along the eaves figure 2 29 below.

The eaves detail shows where the roof members and coverings meet the wall of the dwelling. Flat roofs are built with a slight pitch of at least 1 8 per foot so water can drain either to centralized drains scuppers or a gutter system. With flat clay roofing tiles the first course may be raised with a special starter tile as shown at left in figure 2 27 or by a metal eaves closure raised fascia or wood cant strip. Fix a plywood board or proprietary tray to provide continuous support to underlay to prevent water retaining troughs.