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Technical Information

Concrete Roofing Products Ventilating Tile

The Concrete Roofing Product Vent tile (subsequently referred to as the product) is manufactured to all main profiles and colours, and availability is usually ex-stock. Any special requirements could be made to order.

The product uses a standard roof tile as a concrete cap to match the tile colour. The mesh grill is of aluminium and attached to the front of the cone in order to prevent intrusion of foreign bodies. A 110mm spigot is fitted to the underside of the tile to vent the roof void or alternatively with a flexible pipe attached to the spigot, can be used for mechanical adaptation.

The product conforms to BSS473/550 Part 2-1990, the relevant designations begin No 13, 17.2, and 20.3 and has free air flow of 7200mm per unit.

The product is NOT to be used in conjunction with any gas combustible appliance. A gas ventilating ridge is made for this purpose.

Slates / Stones / Lintels

Architects, Specifies and Builders have always appreciated the beauty and aesthetic appeal that natural quarried slates and flags afford. Today, however a worsening problem exists with short supply and prohibitive costs making it impossible or too expensive to specify traditional materials once taken so much for granted. With this in mind, we have created a range of handmade slates and tiles which are individually cast in moulds taken from the original, quarried material. The finished product faithfully recreates the charm and individuality of the natural looking roof-at an affordable price.
We have combined modern technology with specialised moulding techniques to produce a range of quality slates which offer long term durability, strength, character and guarantees that no two slates are exactly alike. Celstone slates are available in various finishes – Welsh Grey, Lakeland Green and Random Stone. These products are fixed by traditional methods.

Technical Details

These products are a composition of inorganic materials which consist of a matrix of hydraulic cement and fine aggregates with an alkali resistant chopped strand glass fibre, which provides tensile and flexural strength greater than the required by the British Standard. Coloured throughout with colourfast pigments. Random stone, colours include light, dark and bespoke.

Extras include:

  • Batten Plans
  • Ridges and accessories
  • Specials, made to order

The overlap depends on pitch, exposure and fixing is by head pegs. Random stone roof tiles are approximately 50% of the weight of natural stone. 16 sizes are available from 300 to 840 mm, with random widths.

Sizes & Weights

Lakeland Green 500 x 305 mm approx. 2.25kg
Welsh Grey 500 x 305 mm approx. 2.1kg
Random stone from 350 x 775 mm in length 
65kg/sq.m. roof area NB. ALL SIZESD ARE NORMAL


500 x 305 mm – 15.11 No.per sq.m. Typical head lap and exposure.
Random Stone – quotations given upon receipt of detailed sketch

Delivery & Storage

Celstone slates and tiles are packed in crates and should be kept covered and dry on site prior to fixing.

Roof Pitch

The recommended minimum roof pitch is 22½°


Non-combustible and complies with Class O requirements to BS 476 Pt.4,5,6,7 and 8 with negligible smoke production


Water vapour permeability to BS 3177 and water permeability BS473.550

Durability & Weathering

G.R.C. has a history of many years in external situations world-wide and its performance has been regularly monitored throughout this period. The correlation of results between ‘real life’ testing and laboratory simulated tests has been sufficiently close to enable a predicted life expectancy of fifty years or more for the products mentioned. Ultraviolet light has no degenerative effect on G.R.C. composites. All pigments used for Portland cement and products are to BS 1014 standards.


With a diminishing pool of skilled tradesmen and escalating costs, particularly with the more specialised items such as arched lintels.

The two most widely accepted methods of manufacturing brick lintels either involves the factory cutting of individual bricks then building them of a steel lintel or other form work; alternatively, casting in or bonding onto a precast concrete lintel with bricks cut into thin slips. Whilst these methods are perfectly adequate, they are also expensive.

There is now a third option, G.R.C. precast lintels, made possible by combining specialised, state of the art, moulding techniques with the time proven versatility of glass fibre reinforced cement compounds.

The finished product faithfully recreates the textures to the finest detail.

Most brick colours and hues can be matched very closely using the highest quality inorganic metal oxide pigments. These are totally colour fast and will not fade. A slight change of colour could occur due to the natural weathering process, however this would be minimal and not permanent.


The following are a selection of independent references on G.R.C. composition. Building Research Establishment Information Papers IP36/79, 1979; IP/82, 1982; and CP12/76; 1976 –BD6432; B.A. Proctor “G.R.C. Principles and Practice” Proceeding of International Congress on G.R.C. Brighton, G.R.C. Association 1977 pp 51-67.

Ridges and Ridge Products

Concrete Roofing Products ridge tiles and associated products are manufactured from sand aggregate, B.O.C cement, water and colouring agent, under high comp action and extrusion process. The smooth faced products have a through body colour and some finished with an acrylic coating or a granular finish. Our ridges come in 3’ and 18” lengths and varying angles.

18” ridges are available in segmental, universal, 90° and 115°, 3’ are available in 90°, 105° and 115°, Cap angle ridges are available in 90°, 105° and 115°.

Standard colours of 3’ ridge are available in through colours of Buff, Buff/Black, O/Stone Broad rib, Slate Grey and Brown.

All Concrete Roofing Products, ridges and fittings must be laid and fixed in accordance with BS5534, Part 1, 1978.


The In-line Air Vent Ridge is available in Segmental and Angle profile.

The In-line Air Vent consists of a slotted PVC base unit, mechanically fixed to a concrete ridge tile. The air flow is provided by the shortening of the legs along the length of the ridge, and as such allow the ridge to sit level with the remainder of the ridge line, giving a more aesthetic appeal than concrete/plastic capped vent ridge.

The In-line Air Vent Ridge can be conventionally mortar bedded but is also compatible to all main manufacturers dry ridge systems.

An Air Vent Ridge adapter and terminal is available which protrudes 225 mm below the ridge line, into the roof space. This extrusion is adaptable to mechanically extracted system and can be connected to ducting via the adapter and flexi-pipe.

The In-Line Air Vent Ridge is available in all through and granulated colour finishes, and complies to B.S. 5250.

The Air Vent Ridge are available in Segmental, Half-Round, Universal, Angled or the 3’ Profile.

These all come in a comprehensive range of colours. They can be assembled with a Plastic Insert if required. The Vent Ridge complies to B.S. 5250, and provides a Free Air Flow of 14000 mm/Unit.

N.B. The Ventilating Ridge is NOT to be used in conjunction with Gas combustible Appliances.

Gas Vent Terminals are available in all profiles and colours. It is constructed from pre cast concrete and the design provides maximum cross sectional areas of outlet in order to reduce the resistance to flow of combustion products. Set pins are positioned at 330 mm centres to accommodate and “R-type” adapter, (5”). Vent openings have a stainless steel grill fitted to prevent intrusion by birds.

The Gas Vent Terminals are certified (Certificate No C26349) to comply with the relevant requirements of B.S. 1289: Part 1: 1986. It is technically suitable for inclusion in the British Gas List of flues and Terminals.

All fittings can be supplied where required i/e “R-type” Adapters (4” and 5”), Extension Boxes and Flexi-Pipes.