Roof Ventilation - The Only Guide You Need to Read

Roof Ventilation - The Only Guide You Need to Read - Beddoes Products

Words: 2137 ūüíĽ¬†Read time: 10 mins ūüďö¬†

Writer: Scott Beddoes ūüĎ®ūüŹĽ‚ÄćūüíĽ

Roof ventilation is one of those problems you know you should sort out, but you ignore it until it's too late.

You know those things that always seem to stay at the bottom of your to-do list?

Roof ventilation is the definition of one of those things!

And if it stays at the bottom, you could be running the risk of condensation and damp.

So it's important that you get roof ventilation right.

This Roof Ventilation Guide will show you everything you need to know, in one neat place.

And, you'll find out how to choose the best option for you and your home.


Roof Ventilation Requirements UK

To meet UK roof ventilation requirements, you have to provide enough ventilation to avoid condensation in the roof space.

Ridge or high-level ventilation should be equivalent to a continuous opening of 5mm at the highest point of each roof slope.

For a roof pitch of 15¬į or more, you should provide ventilation equivalent to a 10mm slot running the full length of the eaves.

And for a mono-pitch roof, you need cross-ventilation, plus the equivalent of a continuous 5mm slot and some eaves ventilation.

Sound confusing? We made the basic drawings below to give you a better idea. 

We refer to the cold roof section in the ventilation segment of 7.2.15 by the National House Building Council (NHBC).

roof ventilation requirements uk


The Problem with Roof Ventilation

Quick history: when houses used to be built, the roof was installed over a breathable membrane.

As the name suggests, a breathable membrane is designed to let your home ‚Äúbreathe‚ÄĚ.

But in recent years, the effectiveness of these membranes has been questioned.

The introduction of¬†loft insulation has done wonders for keeping our homes warmer. But it can also reduce the effectiveness of eaves vents ‚ÄĒ sometimes blocking them completely.

And a warmer house means more potential for condensation.


Condensation in Loft - What Causes It?

So what actually happens when you don’t have enough roof ventilation?

Well, firstly, warm air rises and meets the inside surface of the roof.

And then the temperature difference causes the moisture to condense forming condensation.

Now, heat and moisture is produced by 3 main activities:

1ÔłŹ‚É£ Cooking

2ÔłŹ‚É£ Drying your clothes

3ÔłŹ‚É£ Hot baths or showers (see our in-depth post for how to stop bathroom condensation)

And without the right amount of roof ventilation, it won't be long before daily activities start contributing to condensation or damp.

So, in an ideal world, you want to catch it and do things to prevent it before it develops any further.

Because the longer you leave it, the more damage it will do to your savings that could be better spent on things you like spending money on.


Damp Problems in the House

Damp in your house can cause these 3 problems:

‚úÖ Wood rot

✅ Black spot mould 

✅ Health risk for people with respiratory problems

Thankfully, condensation and damp can be treated fairly easily.

You might even be able prevent the problems before they develop. 


Loft Condensation Solutions

There are 2 main solutions to the problem of loft condensation:

1ÔłŹ‚É£¬† Vapour barrier¬†membrane
2ÔłŹ‚É£¬† Roof¬†vents

    Vapour Barrier Membrane

    Vapour Barrier Membrane - Beddoes Products

    A vapour barrier membrane is a thin layer placed under the insulation between your loft and your upstairs rooms.

    It is designed to prevent warm moist air from moving up from the house into the roof space. And it does that job well.

    However, there are still points like the edges where air can still get through.

    And when it comes to improving ventilation or adding extraction (which we'll go into later), you're going to need some type of roof vent. 


    Best Types of Roof Vents for Houses

    Today, new builds require roof tile ventilation to pass building regulations, and owners of older homes are installing roof vents to improve ventilation.

    There are many different types of roof vents for houses on the market. And each option has it’s good and bad points.

    But which type of roof vent is the best?

    Let's quickly go through them here to save you some time.

    I'll tell you the pros and cons of each and give it a star rating out of 5.

    Soffit Vent

    Soffit vents are installed under the eaves of a roof. They let fresh air up into the loft to improve air circulation. This prevents loft air from going stale. When combined with roof ventilation tiles they work efficiently to draw air in through the soffit vents and exhaust warmer air through the ventilation tiles.

    Soffit Vent - Beddoes Products

    Pros Cons
    Easy to install Designed for air intake
    Unlikely to be blocked by snow Different roof vents needed to exhaust air

    ¬†Product rating: ‚≠ź‚≠ź¬†


    Fascia Vent

    Fascia vents are installed over the fascia boards to provide low level ventilation. They could offer a better alternative to soffit vents, because soffit vents can accumulate dust and debris. This can require regular maintenance and cleaning work.

    Fascia Vent - Beddoes Products

    Pros Cons
    Can't see them like soffit vents Not an easy DIY option
    Mesh keeps out insects Can leave little space for guttering install
    Can be blocked by loft insulation

    ¬†Product rating:¬†‚≠ź‚≠ź¬†


    Cowl Vent

    Cowl Vent - Beddoes Products

    A cowl vent is a hooded roof tile vent designed to replace existing roof tiles. They can also be connected to a bathroom extractor fan using a flexible pipe adaptor.

     Pros Cons
    Easy to install Doesn't look great
    Prevents draughts and wind-driven rain Breaks appearance of roof
    Prevents entry of bugs and insects

    ¬†Product rating:¬†‚≠ź‚≠ź‚≠ź‚≠ź


    Lap Vent

    Lap vents slip in between an overlap in the horizontal under-sarking inside the loft, providing an air path for the wind blowing up the face of the roof outside.

    Pros Cons
    Simple, easy, and effective Safe floor in loft needed to work on for internal fitting
    Can install from inside - no need for external access or getting on the ladder Might not provide as much ventilation as roof ventilation tiles

    ¬†Product rating:¬†‚≠ź‚≠ź‚≠ź


    Dry Ridge Vent

    Dry ridge vents can be used on the apex of a roof to provide high level ventilation and exhaust moisture. Dry ridge vents aren’t really designed to be used as vents alone. They are more of an exit point than a source of ventilation. They can be used in combination with other forms of lower level ventilation such as eaves vents or soffit vents, fascia vents, or roof ventilation tiles.

    Pros Cons
    If positioned on the apex of the roof with the felt or under-sarking suitably cut immediately beneath, they do provide excellent natural air movement If you live in an exposed location and have large soffit vents as well, ridge tile vents have been known to cause too much ventilation on very windy days, possibly blowing the insulation about near the edges

    ¬†Product rating:¬†‚≠ź‚≠ź


    Slate Vents

    Slate vents are designed to replace existing roof slates. Slates come in 2 standard sizes - 600 x 300mm (24 x 12 inch) and 500 x 250 mm (20 x 10 inch).

    You can get them in plastic and sometimes real slate. They have a grille and underbase that allow air to flow through the vent and out of the roof. Most slate vents have the option of a pipe adaptor fitting to create a connection for bathroom extractor fans and soil vent pipes.

    Slate Vents - Beddoes Products
    Pros Cons
    Easy to fit Must be fitted from the outside
    Look better than cowl vents

    ¬†Product rating:¬†‚≠ź‚≠ź‚≠ź‚≠ź‚≠ź


    Roof Tile Vents

    Roof tile vents are by far the easiest professional solution to roof ventilation problems.

    They are easy to fit either during the process of installing a new roof, or retrofitting to older existing roofs. One vent replaces one tile.

    Roof Tile Vents - Beddoes Products

    There are roof tile vents designed to fit most tile profiles on the market.

    You can buy them in the same colour as your existing roof tiles to maintain the appearance of your roof.

    If you're venting your extractor fan through your roof, a roof tile vent is almost certainly your best solution.

    How Roof Tile Vents Work

    How Roof Tile Vents Work
    Pros Cons
    Easy to install Must be fitted externally
    Look good with multiple colour options  
    Available for most types of roof tile

    Product rating:¬†‚≠ź‚≠ź‚≠ź‚≠ź‚≠ź

    Which Roof Tile Vent Do I Need?

    There are 5 ways you can find out which roof tile vent you need.

    1. Find a spare tile and check the back for brand name and model.
    2. Ask a professional roofer.
    3. Use Google images to look for similar roof tiles.
    4. Visit tile manufacturer websites such as Marley, Redland and Sandtoft.
    5. Send a photo via the Contact Us page at

    Roof Tile Vent Dimensions

     Tile Name Length (mm) Width (mm) Roof Tile Vent
    Marley Modern 420 330 Marley Modern Vent Tile
    Marley Ludlow Plus 387 230 Marley Ludlow Plus Vent Tile
    Marley Ludlow Major 420 330 Marley Ludlow Major Vent Tile
    Marley Mendip 420 330 Marley Mendip Vent Tile
    Marley Wessex 420 330 Marley Wessex Vent Tile
    Marley Plain Tile 267 165 Plain Tile Vent
    Marley Edgemere 420 330 Marley Edgemere Vent Tile
    Marley Double Roman 420 330 Double Roman Vent Tile
    Redland 49 382 226 Redland 49 Vent Tile
    Redland Renown 418 332 Redland Renown Vent Tile
    Redland Mini Stonewold 418 334 Redland Mini Stonewold Vent Tile
    Redland 50 Double Roman 418 332 Double Roman Vent Tile
    Redland Delta 430 380 Redland Delta Roof Tile Vent
    Redland Grovebury 418 332 Redland Grovebury Vent Tile
    Redland Plain Tile 268 165 Plain Tile Vent
    Redland Stonewold Mk2 430 380 Redland Stonewold Mk2 Vent Tile

    Let's use the example of the Marley Ludlow Major roof tile:

    Find the Ludlow Major tile on the Marley website here: Marley Ludlow Major

    Let's say you decide using the photos that you have the 'Dark Red' version.

    Now go to the Beddoes Products website for the Marley Ludlow Major Vent Tile here: Marley Ludlow Major Vent Tile and select the 'red - sanded' option.


    What Colour Should I Choose?

    Roof ventilation tiles come in 5 basic colours:

    • Grey
    • Terracotta
    • Brown
    • Red
    • Black

    Most manufacturers produce tile vents in smooth plastic in these colours.

    Some roof tiles are different. They might be a mixture of 2 colours or old and weathered, causing the colour to change.

    In these situations, the basic colours can stick out among your roof tiles like a sore thumb.


    How Can I Colour Match My Roof Tiles?

    At Beddoes Products, we manufacture everything in-house. Our products come in any colour in smooth or granular finishes. We can also colour match to existing tiles. All you need to do is send us a photo.

    Check your tile manufacturers’ website and search for your tile. Some brands use different names for similar colours to their competitors. For example, Marley Old English Dark Red is a close match to Redland Farmhouse Red.

    Send us an email to ask for advice about your colour, or leave a note with your order.


    How Many Roof Tile Vents Do I Need?

    Finding the right number of roof tile vents can be more of an art than a science. It depends on your house’s age, property type and location. 

    It would be useful to ask for advice from a professional roofing expert, but you might want to make your own estimate.

    Consider adding slightly more ventilation than is needed to allow for extreme weather conditions, while keeping costs as low as possible. Try to find a balance.


    1. Find total airflow required.  Discover the length of the ridge of the roof in mm.

     Length (mm) x continuous airflow required.

     Example: 10m long roof requiring 5mm continuous airflow.

     10 metres  = 10,000mm long roof followed.

     Then 10,000mm x 5mm = 50,000mm2 airflow required.


    2. Work out the number of vents required, asking how many vents it would take to provide the same amount of airflow. 

    Total airflow (provided by first calculation) √∑ airflow per vent.

    Example: For the Beddoes Products Plain Tile Vent with an airflow of 7,500mm2

    50,000mm2 √∑ 7,500mm2 = 6.67 vents (which would require 7 vents).


    3. Calculate the centres of the vents, checking how far apart they need to be.

    Length of roof √∑ number of vents

    Following the above example: 10,000mm long roof √∑ 7 = Centres of 1,429mm (1.5 metres rounded up).

    Instead of putting 7 on one side of the roof, you would stagger them on opposite sides to get the best airflow.

    Staggering would mean placing 4 vents on one side at 3 metre centres. Then placing the remaining 3 vents on the opposite side at 3 metre centres, but in between the 4 on the other side.

    Think of it like this: you you were to draw a line between the vents on both sides, it would look like a zigzag.


    How to Fit Roof Tile Vents 

    The informative video below from the Fixmyroof YouTube channel demonstrates how to fit roof tile vents.

    These are the simple steps described in the video:

    • Remove roof tiles from the area where vent will be fitted
    • Make a cross-cut in the underlay
    • Fold out the top piece of felt and nail securely
    • Prepare pipe adaptor and flexi pipe for connection (if installing for bathroom extractor fan)
    • Re-position and nail tiles around the vent area
    • Position and nail roof ventilation tile
    • Complete positioning of remaining roof tiles

    Keep in mind that these are the instructions for the Marley Ludlow Plus Vent Tile and Redland 49 Vent Tile.

    Other vents will be similar but may vary slightly. 

    Where Can You Buy Roof Tile Vents?

    Builders Merchants and DIY Stores

    Buying in-store can be good if you’re lucky. You can see the product close-up to check suitability and quality.

    The problem is most stores only have a small range of products with limited stock. Colour choices will also be limited.


    eBay has more product options than most builders merchants. If you search regularly, you might pick up some cheap deals from someone selling old stock.

    Beddoes Products eBay Shop


    Online Stores

    Online roof tile vent stores have the biggest range of products with the best colour flexibility.

    You could go directly to the big roofing stores. However, it might be better to Google search specific terms like ‚ÄúMarley Ludlow Major Vent Tile‚ÄĚ to find exactly what you‚Äôre looking for.

    I prefer this method because it means less pages to click through trying to find the right product category on bigger roofing websites.

    Beddoes Products Online Store



    In this guide, you've learnt how to decide whether you need roof ventilation, how to choose the best roof ventilation tiles for your home, how to select the right roof tile vent, how to find your colour and where to buy from.

    Now it's time to apply everything.

    Browse our roof tile vents full range.

    Need help? Head over to our Contact page.  

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