Kevin Taylor, Training and Technical Support Manager at Marley gives a simple checklist guideline and practical tips to make sure the fascia installation as smooth as possible.
The fascia is a vital part of the overall roofing structure and helps to comply with BS 5534 (slating and tiling for pitched roofs and vertical cladding – Code of Practice). The code states that the roof slates and tiles at the eaves should be supported in substantially the same plane as the main roof.
This means setting the fascia board to the correct height so the tiles neither noticeably drop nor kick up. If not sufficiently supported tiles and slates can drop, with the result of unsightly gaps below the second course of tiles. In addition, if the gap is large enough, it could mean the roof space is exposed to driving rain if it is not addressed before the tiles are laid.
If the fascia board is set too high, the bottom row of tiles will kick up and the risk that they could be sitting below the recommended pitch. Too much kick at the eaves can also cause flat spots or even a negative fall on the underlay/support trays which could lead to ponding and eventually water ingress. This can be a concern where the roof pitch is equal to, or close to, the minimum pitch of the roof tile.
Setting the fascia
There are three key factors involved in setting the correct upstand of a fascia board:
- The type of roof tile or slate specified for the project
- Decisions around whether to include additional over-fascia vents
- The roof pitch
On site
It is always best to perform a simple check on site using two short pieces of batten and a couple of roof tiles before work commences.
The first batten should be fixed to allow the tail of the tile to finish 50mm over the fascia board on the rake to provide effective drainage into the gutter (although this can be extended for larger gutters or gutters which are off set from the fascia board). The second batten should be fixed at the maximum batten gauge for the roof tile. The two tiles can be laid loosely to double check whether the tiles noticeably drop down or kick up.
If the tiles drop down, then the fascia board will need to be raised, or a timber batten of suitable thickness fixed to the top edge, to make up for the shortfall. This should be installed before any of the roofing materials as well as batten setting out is carried out.
If the tiles kick up, then two checks need to be made. Lay the support tray loosely (or 5U felt or other UV stable carrier) at the eaves and check there is still sufficient fall to guide any rainwater into the gutters.
Using a pitch finder, check the laying angle of the first roof tile. If it is more than 5 degrees below the minimum recommended roof pitch (known as the laying angle of the tile), then the fascia board may need to be lowered or cut down.
For the majority of common roof pitches, upstands totaling between 35mm and 50mm work for most interlocking tiles depending on their thickness, and around 55-65mm for plain tiles. For slates, the upstand should be approximately the batten depth + two thicknesses of slate (e.g., 25mm + 2 x 5mm).
Bell-cast or sprocket eaves
Traditionally, steep roofs, often with long rafters (such as church roofs, spires, and turrets) were designed with bell-cast or sprocket eaves. This is where additional short sections of rafter are fitted to the eaves at a significantly shallower angle to slow the flow of water down before it hits the gutter.
However, such details are not suitable for interlocking tiles and should only be used for smaller format materials such as plain tiles and small slates and cedar shingles.
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