Dry Ridge Systems: What's in the Kit, Why It's Required, and How to Check It's Done Right

Your roofer finishes the ridge and you look up from the garden. The ridge tiles are on, they look straight enough, job done. Six months later, during a January storm, water comes through the bedroom ceiling directly below the ridge line. The roofer who bedded those ridge tiles in mortar didn't mechanically fix them, the mortar cracked in the first frost cycle, and now you're paying twice: once to strip the ridge, once to install it properly with a dry ridge system. This happens constantly. It's also a building control failure that can hold up your completion certificate.

What it is and what it's for

A dry ridge system is a kit of components that mechanically fixes ridge tiles to the apex of a pitched roof without using mortar. The "dry" means no wet mortar mix, no waiting for it to cure, no cracking when it dries out.

The kit replaces the traditional method where a bricklayer or roofer would trowel a thick bed of sand-and-cement mortar along the ridge, press the ridge tiles into it, and point up the joints. That mortar bed has always been the weakest point of a UK roof. It cracks, it absorbs water, it gets blown out in storms. Every few years it needs repointing, and eventually it fails completely.

A dry ridge system fixes each ridge tile individually with a stainless steel screw through a metal clamping plate into a timber ridge batten. A ventilated membrane roll runs along the apex underneath the ridge tiles, keeping rain and snow out while letting warm, moist air escape from the roof void. The whole assembly is mechanical, not reliant on adhesion, so it handles thermal movement, wind uplift, and frost cycles without degrading.

On any new build or extension in the UK, building control expects to see a dry ridge system. This isn't optional.

Why it's now required

The key standard is BS 5534:2014+A2:2018, the code of practice for slating and tiling. Since February 2015, this standard has required all ridge and hip tiles to be mechanically fixed. Mortar alone is no longer acceptable as the primary restraint.

BS 5534 is technically a code of practice, not primary legislation. But Building Regulations require roofs to be weathertight (Approved Document C), and building control bodies use BS 5534 to assess whether your roof meets that requirement. In practice, if your extension roof doesn't have mechanical ridge fixing, your building control inspector will flag it.

A companion standard, BS 8612:2018, sets specific performance requirements for dry-fix products: wind load resistance, rain and snow ingress prevention, UV and freeze-thaw durability, and profile compatibility testing. Any dry ridge kit that meets BS 8612 satisfies the BS 5534 requirement. Look for BS 8612 compliance on the product packaging.

NHBC Standards (Chapter 7.2, Section 7.2.19) mirror this: ridge and hip tiles must be mechanically fixed with self-sealing non-ferrous fixings into timber battens. NHBC inspectors check for it. A mortar-only ridge on a new build is a notifiable defect.

What about older houses and period properties?

There's no formal exemption in BS 5534 for listed buildings or conservation areas. But Building Regulations allow alternative compliance routes, and building control officers have discretion. On a Victorian terrace where plastic fittings would look out of place, a hybrid approach (mortar bedding with discreet mechanical fixings underneath) can satisfy the standard while preserving the roof's appearance.

If you're working on a listed building, consult your local building control and the relevant heritage authority (Historic England, Cadw in Wales, or Historic Environment Scotland) before specifying materials. Private approved inspectors tend to offer more flexibility than local authority building control on heritage roofing.

What's in a dry ridge kit

A standard 6m kit contains everything you need for approximately 6 linear metres of ridge. The components work together as a system, and each one serves a specific purpose.

Ventilated roll membrane (one roll, typically 300mm wide x 6m long). This is a UV-stabilised polypropylene fleece with a colour-coated aluminium strip along each edge and a butyl adhesive strip on the underside. It drapes over the ridge apex and sticks to the top course of main roof tiles on each side. The fleece is breathable, letting warm air from the roof void escape through the ridge while blocking rain, snow, and insects. Most systems provide 5,000mm2/m of ventilation, equivalent to a continuous 5mm gap along the full ridge length. The Redland DryVent system provides 10,000mm2/m for roofs that need higher ventilation rates.

Ridge unions (also called fillers or ridge-to-ridge seals). Typically 13 per 6m kit. These are plastic spacers that sit between adjacent ridge tiles, creating a consistent gap and a weather seal at each joint. They stop rainwater from being driven sideways under the ridge tile overlap.

Clamping plates. Metal plates that sit on top of the ridge tile and distribute the load from the fixing screw. They grip the underside of the ridge tile's lip and pull it down tight against the ventilated roll.

Stainless steel screws with rubber washers (13 per 6m kit, typically 75mm or 100mm long). These drive through the clamping plate, through the ridge batten, and into the timber. The rubber washer under the screw head creates a waterproof seal at the fixing point.

Batten support brackets (10-11 per 6m kit). These metal brackets screw into the rafters and support the ridge batten at the correct height above the tile surface. They set the gap between the ridge batten and the top course of tiles, which determines how the ridge tile sits.

Some kits also include block-end caps for finishing the ridge at gable ends. If yours doesn't, buy them separately. A ridge line that stops abruptly without an end cap looks unfinished and lets rain in.

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Types and brands

The major UK brands are Klober, Manthorpe, Marley, and Redland (BMI). All make BS 8612-compliant systems. The differences come down to price, ventilation rate, tile compatibility, and guarantee length.

For most extension work, the Klober or Manthorpe kit does the job. The Marley RidgeFast is a good choice if you want to match Marley ridge tiles exactly, and the hydrophobic membrane sheds water better in exposed locations. The Redland DryVent is worth specifying if your roof has a span over 10m or a pitch over 35 degrees, where Building Regulations (via BS 5250) require higher ventilation rates.

Compatibility matters

Not every dry ridge system works with every ridge tile profile. Ridge tiles come in half-round, angle (90-degree and 120-degree), universal, and pantile profiles. The foam fillers and ridge unions in the kit must match the profile of your main roof tiles. A half-round ridge union won't seal properly against a low-profile interlocking tile, and an angular filler won't sit against a pantile.

Check the manufacturer's compatibility chart before ordering. Most "universal" systems cover the common concrete profiles (Marley Modern, Edgemere, Redland 49, Grovebury, Sandtoft Double Roman) and standard half-round ridge tiles. High-profile pantiles and some clay profiles need a profile-specific kit.

How to work with it

You won't be installing this yourself (it's done on scaffolding at ridge height), but understanding the process means you can check your roofer's work.

Installation sequence

The dry ridge goes on as the final stage of roof covering, after all courses of main tiles are laid.

First: fix the ridge batten. Batten support brackets screw into the rafters at each rafter position along the ridge. The ridge batten (25x50mm treated timber, same as the roofing battens) sits in these brackets. The bracket height sets the gap between the ridge batten and the top tile course. This gap must be consistent, because it determines how level the ridge tiles sit.

Second: roll out the membrane. The ventilated roll unrolls along the ridge, centred over the apex. The butyl adhesive strip sticks to the top surface of the main roof tiles on each side. Overlaps between rolls should be at least 75mm. The membrane must be applied in dry conditions. If the tiles are wet, the butyl won't adhere and the membrane will lift in wind.

Third: place ridge unions. These clip onto the ridge batten at each ridge tile joint position, typically every 330mm (matching the ridge tile length).

Fourth: place and fix ridge tiles. Each ridge tile sits over the membrane and unions. The clamping plate goes on top, then the stainless steel screw drives through the plate, through the ridge batten, and into the timber. Tighten until the rubber washer compresses but don't overtighten (you'll crack the ridge tile).

Fifth: fit end caps. Block-end caps finish the ridge at gable ends.

A competent roofer will get through a standard extension ridge of 5 to 6 metres in a few hours.

Ventilation

A dry ridge system isn't just a fixing method. It's a ventilation strategy. The continuous 5mm gap along the ridge allows warm, moisture-laden air to escape from the roof void. This is high-level ventilation, required by BS 5250:2021 (the code of practice for moisture management in buildings).

Traditional mortar ridges block this ventilation path entirely. That's one reason mortar-bedded roofs are prone to condensation in the roof space. When you see a roofer poking holes in the mortar every few ridge tiles ("weep holes"), they're trying to provide ventilation that a dry ridge system delivers by default across the full ridge length.

How much do you need

Measure your ridge length in metres. On a simple rear extension, this is the width of the extension.

Divide by 6 (the coverage of a standard kit). Round up to the next whole number. That's your kit count.

Worked example: a 4.5m wide extension needs one 6m kit, with 1.5m of membrane left over. A 7m wide extension needs two 6m kits (12m total, 5m spare). Keep the spare membrane roll for any future repairs.

If your extension has hip ridges (where sloping roof edges meet on a hipped roof rather than a gable), measure those separately. Hip ridges need the same dry ridge system, plus hip support trays at the foot of each hip. Budget one kit per 6m of combined ridge and hip length, plus hip-specific components.

Cost and where to buy

For a typical extension with a 5 to 6 metre ridge, materials (one dry ridge kit plus ridge tiles) come to a hundred pounds or so. Labour is included in the overall roof covering price, as the roofer fits the dry ridge as part of tiling the roof, not as a separate job. If you're retrofitting a dry ridge to an existing roof (stripping old mortar and replacing), expect a total project cost of several hundred to over a thousand pounds for a standard semi-detached house.

Where to buy

Dry ridge kits are stocked by all the main merchants. Screwfix and Toolstation both carry the Klober range in store, making them the easiest option for a single kit. Travis Perkins, Jewson, and specialist roofing merchants carry the full range from all four brands and can advise on compatibility with your tile profile.

Online roofing specialists (Roofing Superstore, DryVerge and Roofline Direct, Roofgiant) often beat the big merchants on price by 10 to 20%, particularly on Klober and Manthorpe kits. It's worth comparing online prices against your local merchant before ordering.

Your roofer will usually supply the dry ridge kit as part of their materials order. Check what brand they're quoting. If they specify Klober Economy and you're paying for Marley RidgeFast, that's a conversation worth having. The price gap between budget and premium kits is noticeable.

Alternatives

The only real alternative to a dry ridge system is mortar bedding with mechanical fixings. This hybrid approach uses traditional sand-and-cement mortar to bed the ridge tiles, with stainless steel nails or screws driven through the mortar into the ridge batten to provide the mechanical restraint that BS 5534 requires.

This hybrid method satisfies building control on re-roofing and heritage projects where the appearance of visible plastic fittings is a concern. It's slower to install (the mortar needs to cure), it still requires periodic repointing, and it blocks the ridge ventilation that a dry system provides. But on a Victorian terrace where the street elevation matters, the mortar-bedded ridge looks right.

For new extensions, use a dry ridge system. Building control expects it, NHBC standards require it, and it'll outlast a mortar ridge by decades. It's also faster to install.

Dry ridge vs dry verge

Homeowners often confuse these. A dry ridge system caps the apex of the roof (the top, where two sloping sides meet). A dry verge system finishes the gable edges (the sloping sides where the tiles end at a gable wall). They're different products solving different problems, but on a fully dry-fixed roof, you need both. If your roofer specifies dry ridge but not dry verge, you'll end up with mechanical fixing along the top and crumbling mortar undercloak on the gable ends.

Where you'll need this

• Roof covering - mechanical fixing system for ridge tiles, required by building control on any new pitched roof

Common mistakes

Leaving old mortar on tile edges. When converting from a mortar ridge to a dry ridge, every trace of old mortar must be chipped off the ridge tile ends. Mortar residue prevents the clips and unions from seating properly. This is the number-one complaint on roofing forums, and it leads to gaps, rattling, and water ingress.

Applying the membrane in wet conditions. The butyl adhesive strip on the underside of the ventilated roll needs a dry tile surface to bond to. If your roofer rolls it out on a wet morning, the membrane won't adhere and it'll peel up in the first gust of wind. This is a common defect on new-build roofs, particularly when the builder is pushing to get the roof watertight before a weather window closes.

Using the wrong ridge union for the tile profile. A universal dry ridge kit covers most common concrete profiles, but high-profile pantiles and some clay ridge tiles need a specific filler. If the foam or union doesn't match the tile's shape, gaps appear between the ridge tile and the main tiles below. Those gaps let in rain, insects, and birds. Check the compatibility chart.

Skipping the hip support trays. On a hipped roof, the dry ridge system extends along the hip ridges as well as the main ridge. Hip support trays sit at the foot of each hip where it meets the eaves. Omitting them is a common shortcut that leaves an exposed gap at the most vulnerable point.

Assuming building control or NHBC inspection caught everything. Forum reports from new-build homeowners document NHBC final inspections that passed clearly defective dry ridge installations. Don't rely on the sign-off. Walk around your property at ground level with binoculars after the ridge is done. Look for: visible daylight gaps between ridge tiles, loose or lifted membrane edges, missing end caps, and ridge tiles that are visibly out of alignment. If you can hear ridge tiles rattling in wind, something is wrong.

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