Tile vents and eave vents are often used when we re-roof a house with tiles but when working with slate these do not fit the old style of construction. On all our re-roofs with Natural slate, and man made we now use breathable felts so the look of the slate roof is not spoiled
Two makes are Ruberoid and Klober.

Both have agrement certificates .

Links to their sites are at the bottom of this page.

Thanks to Klober for this information.

Code of Practice for Control of Condensation in Buildings.
Moisture should be extracted at source to reduce the risk of water vapour transfer from occupied areas of the roof. To achieve adequate cross ventilation openings should, where possible, be placed on the longer sides of a typical rectangular roof.
If ventilation openings are sited at intervals, they should be of equivalent area to the continuous openings recommended, and avoid stagnant air pockets due to inadequate through-flows. Opening sizes are minimum provisions, with certain constructions there are advantages in increasing these in order to ensure air movement through the roof void. Ensure that ventilation openings cannot be blocked by dust, airborne debris, paint or frost, and that the ingress of rain, snow, birds and large insects is prevented.
A nominal mesh size of 4mm is recommended, which would achieve this and avoid excessive airflow resistance. Consideration should be given to the use of proprietary ventilators where these will avoid problems, or be more practicable in use. The ventilation openings should provide a continuous weatherproof path from the roof void to the outside without impairing the waterproof function of the structure, eg. the roof underlay, vapour control layers or the roof covering.
For pitched roofs where ventilation at high level (eg. at or near the ridge) is recommended, this is in addition to any low level requirement. High level ventilation should never be used on its own as the suction effect created will increase water vapour transfer into the roof void. Thermal bridging should be minimised particularly at the external wall/ceiling junction. and gaps in the ceiling should also be minimised and service openings should be sealed. Where the insulation is at ceiling level and where the eaves ventilation airway is provided between the insulation and the sarking, they should be separated from one another by at least 25mm.


Approved Document part F ‘Ventilation’ (revised 1995) states that: ‘Adequate provision shall be made to prevent excessive condensation in a roof void above an insulated ceiling’. It also draws attention to the BRE report ‘Thermal Insulation: Avoiding Risks’. This has been prepared to give guidance to Approved Document part L - ‘Conservation of Fuel and Power’. In particular it stresses the importance of: a) Ventilating the roof space in accordance with BS 5250. b) Insulating ventilation ducts in the roof space. c) Avoiding cold bridging by carrying loft insulation over the wall plate and butting against the wall insulation. d) Avoiding freezing of water in the tanks and pipes by insulating pipe airflows and the top and sides of water tanks. VENTILATION. AN EASY SOLUTION. The only practical way of preventing condensation in the roof space is through effective ventilation. By promoting cross currents of air, the entire roof void will be kept well ventilated, dispersing any water vapour before it can condense. To be effective, the ventilation has to be sufficient to cope with the worst situation when moisture is produced - typically early morning or evening, during spells of damp, cold weather when the air is still. In recognition of the increased importance of controlling condensation, both the Approved Document of the Building Regulations and the British Standard relating to ventilation have been revised. A summary of the main requirements which apply generally to all new and existing buildings is given here, with specific situations tabled overleaf. It should be noted, however, that anything differing markedly from typical domestic situations may need special consideration. The Klober roof ventilation products featured on the following pages have been specifically designed to provide the most simple and cost-effective solution to condensation. They can be used in new build, re-roofing and refurbishment situations, and through their universal nature will simplify specifications and speed installation.


Condensation is a symptom of modern living and of today’s preoccupation with saving energy by minimising heat loss. The increased presence of central heating, showers and modern domestic appliances produces greater amounts of water vapour in the home.Even repiration gives of 1 litre of water per person at night.A tumble dryer alone can give out over 6.5 litres per day. Things get worse by the fact that these moisture-producing activities are often concentrated at certain times of the day, followed by long periods when the house is either unoccupied or unheated. In addition, through greater draught proofing, double glazing and fewer open fire places, ventilation is reduced throughout the home - encouraging this moisture-laden air to rise into the roof space. Here too, natural ventilation is virtually eliminated through the use of an underlay. The traditional roof void is also cold because of the presence of thicker insulation material. So as the warm, moisture-laden air rises from below, it cools, reaches dewpoint, and condenses on cold surfaces. If left unchecked, this condensation can cause severe damage to the fabric of the building. Timber can rot, weakening the structure. Wetting will cause timber and timber-based materials to swell and distort, permanently damaging sarking boards and wall plates. Metal corrosion can occur on components such as roof truss nail plates. Insulation materials will absorb dripping water and lose their thermal effectiveness. Ceilings could be damaged by condensation soaking through. Electrical circuits could be affected. Mould growth will form, and anything stored in the loft could be permanently damaged.

And here is a brief description from Ruberoid


High Performance Breather Membrane Rubershield-PRO is a three layer; highly breathable waterproof membrane, constructed from high tensile spun-bonded polypropylene layers, around a microporous polypropylene film.

The outer layer forms the functional waterproof surface, the middle layer is the breathable waterproof membrane, and the inner layer protects the membrane from abrasion and damage, also giving additional strength. This enables the fabric to allow moisture vapour to pass through, whilst remaining fully waterproof.
Rubershield-PRO has a dark green upper surface, printed with the trade name and head lap lines. Rubershield-PRO is a second-generation breather membrane, conforming to the highest performance and professional standards.
Designed for use as a fully supported or unsupported breathable underlay for tiled, slated or metal roofing systems, Rubershield-PRO is a triple layer engineered fabric, ensuring full moisture vapour permeability, whilst maintaining the highest levels of water resistance. The high vapour permeability and waterproof nature of the membrane, combined with excellent tensile/tear strength, make Rubershield-PRO the professional's choice as the ultimate breather membrane. It is equally suitable whether draped unsupported over rafters or laid directly over insulation.
Rubershield-PRO allows the escape of water vapour from within the roof structure whilst protecting against wind driven rain, snow and dust which may penetrate the main roof waterproofing, providing a permanent quality breather underlay, which will last the life of the roof construction.

Rubershield-PRO BBA Certificate 01/3854 - (Warm roofs and cold ventilated roofs)

Rubershield-PRO BRE Certificate 092/02 - (Cold unventilated roofs)

Use Breathable underlay for tiled and slated pitched roofs. For warm roofs and cold roofs (ventilated and unventilated)


Links:- Ruberoid