Gemini Traditional Sandfaced
Technical Information Sheets
In most cases there is a suitable conventional roof light flashing kit which can be used with our products down to a roof pitch of 15 degrees. Forticrete would not recommend the installation of a conventional roof light below 15 degrees with profiled tiles.
Conventional roof lights when fitted below 15 degrees under certain weather conditions my seep water over flashing. Forticrete have a Low Pitch Roof Window solution, which when used with Forticrete Centurion tiles can be used at a pitch as low as 10 degrees.
All of Forticrete's tiles, with the exception of Centurion (as it has no nailhole) can be used for Vertical Tiling.
Forticrete's single lap tiles need to be (Gemini, Minislate, Senator and V2) will need to be screwed and clipped and the corners will need to be mitred with a lead detail.
Forticrete's Double Lap Tiles (Hardrow and Concrete Plain Tiles) require every tile to be twice nailed, but also have internal and external angles for the corners.
Ventilation and control of ventilation is covered under BS 5250: (Code of Practice for control of Condensation in Buildings).
General information relating to traditional cold roof spaces
Breathable underlays work by transferring moisture laden air from inside the building into the batten cavity (the area between the top of the underlay and the underside of the tiles) where it is allowed to ventilate out between the gaps in the roof tiles or slates.
The gaps in between the tiles or slates will vary depending on the manufacturer and therefore additional ventilation may be required at the eaves or ridge line to assist in drawing the air in the batten cavity out of the roof.
Condensation forming on the back of the roof covering without adequate batten cavity ventilation may result 'Lime Staining' on the face of the tile.
In Forticrete's opinion additional ventilation should be provided at high level in the form of a ventilated ridge line. If the selected tile is flat additional ventilation should be used at the eaves.
Please consult with the tile, and underlay manufacturer for further advice.
General information relating to Warm Roof Spaces
Where the insulation is positioned between and on top of the rafter to the appropriate insulation level and is fully sealed is known as a warm roof.
In this instance no additional ventilation is required.
The Gemini tile clip is not mechanically fixed to the batten using a nail but clips the tail of one tile to the head of an underlying tile. To do this the clip is located on the underlock of the tile and locates under the back of the tile on the course below. The same method applies for the Minislate.
Gemini / Minislate Tile Clips
Slip Clip on to edge of tile
Slide Clip down the edge of tile
Slide Clip down until it reaches the top of the tile below
The Clip is then securely in place
There are two types of clip available, either a tile clip or verge clip and these need to be ordered specifically by the tile being used.
- Tile Clip - Pack of 100
- Verge Clip - Pack of 50
The table below outlines the quantity of Tiles or Fittings on a pallet, as well as, were relevant, the number of tiles in a pack/band.
Tile Pack Quantities
Forticrete can provide a free take off service for roof areas in excess of 60m2 which will give an estimate of how many tiles and fittings you will need to order.
It is important that you fully specify what tiles, fittings and ventilation you require by filling in all parts of the estimate request form which is available as a word document or pdf format.
Side elevations and roof plans will be required with dimensions clearly marked on them.
All estimates are given as a guide that should be checked prior to ordering as any extra costs incurred due to over or under ordering will not be covered by Forticrete.
Please allow up to fifteen working days for return.
Site specific fixing specifications in line with BS5534 should be obtained prior to installation. You can request a fixing specification by visiting myforticreteroof.co.uk.
The number of tiles per m² will depend on the type used and in certain circumstances the pitch. The table below shows the number of tiles per m² for all Forticrete roof tiles.
For duo pitch roofs over 15º and below 35º an eaves ventilation of 10,000mm/m² is required when the insulation is placed at ceiling level and 25,000mm/m² when the insulation is inclined to the rafters. For roof pitches over 35º or where the span across the gable end is greater than 10m, 5,000mm/m² high level ventilation is required.
For mono pitch roofs over 15º the eaves requirements are the same as for duo pitch roofs but high level ventilation is required at all pitches.
For all roof types below 15º the eaves ventilation requirement is 25,000mm/m².
The exposure, location and roof design are all factors that will influence the tile fixing specification.
it is important that site and house type specific fixing specifications in line with BS5534 are obtained prior to installation.
Should you require a full fixing specification for your project, please visit www.myforticreteroof.co.uk.
Our roof tiles have been designed to perform down to their respective minimum pitches.
Below these pitches concrete tiles become purely decorative, and require a secondary waterproof barrier to be employed to carry any water down to the eaves and effectively discharge into the gutter.
There are several manufactures' that provide corrugated sheeting systems but these will always raise the overall height of the roof.
Otherwise a marine plywood deck can be installed with counter battens.
Apertures created in flat sub roof sheeting will have to be fully sealed around the up stands to allow water behind the opening to discharge around it.
Apertures cut into corrugated sub roof systems are not allowed as water in the corrugations above the junction will be trapped.
For further information please call the Technical Department on 01525 244900.
Anchor was taken over by Forticrete, though many of the tiles have since been withdrawn or have passed through product development. Generally the newer tiles do not course in with the older tiles.
One method that can be used is to find a porch or small dormer with the old tiles, use these for repairs, and then use the newer tiles for re-roofing the porch or dormer, as these are generally separate from the main roof.
The following restrictions apply for Centurion tiles at this pitch; the roof is not in an exposed location, it is a single storey lean-to with no hips or valleys with a rafter length less than 5m. All tiles are laid with a minimum100mm headlap. All tiles are tile clipped and verge clipped. Additionally ventilation must be in accordance with British Standards.
The values below are based on the distance from the front of the fascia to the top of the batten with the exception of Hardrow and the Concrete Plain Tiles. The distances for these are based on the front of the fascia to the centre of the batten.
Double Lap Tiles such as Hardrow and Plain Tiles use an Undereaves Tile (often shortened to Eaves Tile), and the batten distance is given for these as well.
The ventilated figures below assume that Forticrete's Eaves System is being used, which has a tray for supporting the underlay behind the Fascia. If an alternative form of ventilation is being used, the figure should be reduced by 6mm to allow for a 6mm plywood fillet to support the underlay.
The following table outlines the size of nail required to fix each of the Forticrete Roof Tiles:
With truss or rafter spacing up to 450mm a 38x25mm batten should be used, spans greater than 450mm up to 600mm 50x25mm batten should be used. If concrete plain tiles are being used, 38x25mm batten can be used up to 600mm spacing.
The use of ¾ tile are used primarily for achieving the broken bond in the Gemini tile only and are used on a verge or a side abutment only. The ¾ tiles are not used on a hip or valley.
For flat profile interlocking tiles the recommended method of protecting a roof/wall junction is to install a continuous cover flashing and a secret gutter. With profiled interlocking tiles the recommendation is to provide a continuous cover flashing in lengths not greater than 1.5m. Further details can be sought for this from the Lead Sheet Association
Wherever possible tiling should be carried out from right to left beginning with a full tile on the very first course then introduce a RH ¾ tile on the course above and on alternative courses thereafter, this will achieve the broken bond in the tiling pattern.
At the opposite verge or hip/valley a tile & half would be introduced and cut to suit.
The LH ¾ would only be used when tiling on a LH verge into a hip or valley.
The LH ¾ tile is minus the interlock and this is an easy way to distinguish the difference between the LH & RH ¾.
As with the RH ¾ tile this would also be used on alternative courses.