Most homeowners only commission one or two pitched-roof installations in their lifetime, so when the quotes come in, knowing what you are actually paying for matters. A compliant, well-installed pitched roof on a Mid Sussex home is not just “tiles on battens on felt”. It is a sequence of carefully detailed steps where any one shortcut – undersized battens, wrong underlay, mortar-only ridge fixing, missing eaves ventilation – becomes a leak or a failure within a decade.
This guide walks through the stages of a real Sussex pitched-roof install, from stripping the existing covering to fixing the final ridge. It covers the UK standards a competent roofer should follow (BS 5534 for slating and tiling, BS 5250 for condensation control, Part L for insulation) and the detail points that separate a proper job from a cheap one.
Before the Scaffold Goes Up
A good pitched roof install starts weeks before anyone strips a tile.
Survey and Specification
Every pitched-roof job worth doing starts with a proper survey. On a re-roof, the survey establishes:
- The existing covering (clay, concrete, natural slate, fibre cement slate) and its condition
- The current pitch (measured in degrees, not the American “rise over run” format)
- Rafter size, spacing, and condition – relevant to any material change that affects roof weight
- Existing flashings, ridge, valleys, and any dormer or chimney junctions
- Insulation and ventilation condition in the roof space
- Wind exposure and BS 5534 Wind Zone for the property
Sussex is predominantly in Wind Zone 2 for BS 5534 fixing purposes, though exposed downland ridges in the north of the county and coastal plots towards Brighton sit in Wind Zone 3. Higher wind zones mean more mechanical fixings per tile. Any roofer quoting a Sussex job without acknowledging the wind zone is missing the starting point.
Planning Permission and Conservation
Most like-for-like re-roofs are permitted development and need no planning application. But there are exceptions:
- Listed buildings: any change to the roof, including matching materials, needs listed building consent
- Conservation areas: Mid Sussex District Council oversees conservation areas in Cuckfield, Lindfield, Hurstpierpoint, Ditchling, West Hoathly, Ardingly and parts of Burgess Hill. In these areas, changing the material (e.g. concrete to slate or vice versa) usually needs an application
- Changes of material on a non-listed non-conservation property: generally PD, but always worth a quick check with the local planning authority
Preparing the Site
Scaffold
A pitched roof install in the UK needs scaffold, not ladders, for both access and for the Working at Height Regulations 2005 (enforced by the Health and Safety Executive, the UK body – not OSHA). Scaffold usually goes up the day before stripping starts and comes down once the ridge is complete.
For detached Sussex houses, scaffold is typically a three-sided or four-sided run. For terraces or semis, party-wall access is arranged with neighbours. Expect the scaffold to stay up for the full duration of the roof works – usually 5-10 days for an average detached house, longer for complex roofs or poor weather.
Weather Protection
UK roof installs routinely run into weather. A professional job includes temporary weather protection – usually heavy-gauge tarpaulins fixed down – so the property is never exposed overnight with an open roof. This is particularly important in Sussex from October through March when consecutive dry days are rare.
Stripping the Existing Roof
The old covering comes off first. On a Sussex re-roof, stripping usually reveals:
- Old felt underlay, often 1F-type bitumen felt on anything pre-2000, which is not vapour-permeable and often brittle
- Original battens, commonly under-sized by modern standards (less than 38 x 25mm) and sometimes rotten at the eaves
- Nail holes in rafters from decades of previous fixings
- Sometimes original lead flashings worth retaining and relaying
Disposing of the Old Covering
Stripped tiles and slates go into a skip. Occasionally, handmade clay tiles in good condition are worth re-using for feature details, patch repairs, or salvage sale. Natural slate that is still sound can be re-laid on the new roof if budget is tight and supply is uncertain – though mixing old and new slate rarely looks right.
Lead flashings are always worth keeping. Lead is a valuable metal and the property owner’s, not the roofer’s.
Inspecting the Structure
With the covering and battens off, the rafters are fully visible for the first time, often in decades. This is when issues get found: rotten sprockets at the eaves, sagging rafters, cracked purlins, historic water damage around chimneys. Any structural work needed gets done now, before the new roof goes on – which is why a professional quote includes a “contingency” allowance for structural repairs that only appear once stripping starts.
The New Underlay
The underlay is not glamorous but it is one of the biggest influences on how long the new roof lasts.
Vapour-Permeable vs Traditional
Modern pitched roof installs use a vapour-permeable underlay (sometimes called “breathable membrane”). These allow water vapour from the house below to escape outwards through the membrane, reducing condensation risk in the loft space.
Older bitumen felt (1F type) is still available and compliant with BS 5250 in certain scenarios, but modern vapour-permeable underlays are the default for almost every Sussex pitched roof install for the past 15 years.
Laying the Underlay
Underlay runs horizontally, starting at the eaves and lapping upwards. Each horizontal roll laps over the one below by 150mm minimum. At the eaves, the underlay dresses into the gutter via an eaves tray. At the ridge, the top rolls meet with a generous overlap.
Getting the eaves tray detail right matters. Water that runs down the underlay (as it will, in any driving rain) must end up in the gutter, not on top of the fascia or behind the soffit.
Ventilation with Modern Underlays
Even vapour-permeable underlays need backup ventilation. BS 5250 requires cross-ventilation in most pitched roof configurations. This is usually delivered via:
- Continuous over-fascia vents at the eaves
- Ridge vents along the ridge line
- Tile vents for specific high-moisture zones (over bathrooms, kitchens)
See pitched roof ventilation and insulation for the full picture.
Battening
Battens take the weight of the tiles or slates. Battens also carry the mechanical fixing loads that BS 5534 requires.
Batten Spec
Under BS 5534, all battens on a new pitched roof must be:
- Graded to BS 5534 (the marked Class A or Class B battens, not unmarked timber)
- Minimum 38 x 25mm for most common tile and slate formats
- Treated for ground contact – softwood battens are pressure-treated against rot and insect attack
Unmarked, untreated, or undersized battens are one of the most common corners cut on cheap re-roofs. They fail silently over 10-15 years as the treatment wears and small knots turn into break points.
Batten Spacing
Batten spacing (the “gauge”) is dictated by the tile or slate being laid. The manufacturer’s technical data gives the exact gauge for the specified product. Gauge calculation determines how many battens are needed across the whole slope and is one of the first calculations a roofer does.
Laying the New Covering
The tile or slate goes on bottom-up, starting at the eaves and working to the ridge. Each horizontal course overlaps the one below by a defined headlap – again, specified by the manufacturer for each product.
Mechanical Fixing (BS 5534)
This is where modern installs differ most from pre-2014 work. Since the 2014 update to BS 5534, every tile and every slate must be mechanically fixed – nailed, clipped, or both. Mortar bedding alone is no longer compliant anywhere on the UK mainland.
What this means in practice:
- Plain tiles: every tile nailed, plus clips in exposed positions
- Interlocking tiles: clipped, plus nails every third or fifth course depending on pitch and wind zone
- Natural slate: nailed, with tail clips in higher wind zones
- Fibre cement slate: hook-clipped or rivet-fixed per manufacturer spec
A Sussex roof installed to the current BS 5534 will survive storm winds that would strip a mortar-bedded 1990s roof. See BS 5534 explained for more detail.
Verge and Eaves Detail
The verge (the side edge of the roof where it meets the gable wall) and the eaves (the bottom edge) are the most exposed details on the whole roof. Good installations use:
- Dry verge systems (interlocking plastic or metal) instead of mortar-only pointed verges. Mortar verges crack within 10-15 years regardless of quality.
- Eaves clips to secure the first course of tiles or slates against uplift.
- Bird and vermin mesh at the eaves to stop access to the roof void through the gap between underlay and tile.
Valley Work
On any roof with more than one slope, the valleys (where two slopes meet in a V) handle the biggest water flows on the whole roof. The options in modern UK installation are:
- Open lead valleys: traditional, long-lasting (80+ years with good lead), requires skilled leadwork. The standard on Sussex conservation properties.
- GRP valley troughs: pre-formed fibreglass, cheaper and quicker, typical on modern estate housing.
- Tiled valleys: swept valleys, laced valleys, or mitred valleys – traditional and beautiful but slow.
All require the underlay to run continuously through the valley. Nothing fails a roof faster than a valley where the underlay stops short. See roof lead flashing and valleys for the detail.
Ridge and Hip
The ridge and hips are usually the last elements installed. Two modern approaches:
- Mortar-bedded ridge with mechanical fixing: mortar bed for weathering, plus a mechanical clip or nail through each ridge tile into the ridge batten. This is the BS 5534-compliant approach. Mortar alone is not compliant on new work.
- Dry ridge systems: proprietary plastic or metal systems that clamp the ridge tiles mechanically with no mortar. Cleaner, faster, and no mortar failure over the roof’s life. Becoming the default on most new work.
Hips follow the same principles. Hip irons at the bottom of each hip stop the first hip tile sliding down.
See mortar in the ridgeline for more on ridge options.
Flashings and Abutments
Wherever the roof meets something else – a wall, a chimney, a skylight, a dormer cheek – a flashing is required. On a quality Sussex pitched roof, this is almost always:
- Lead flashing chased into the brickwork, wedged with lead wedges, and pointed. Code 4 lead minimum, code 5 for high-exposure positions.
- Lead soakers under the tiles at abutments, with the lead flashing covering the soakers on the face.
See leadwork roofing guide for full detail.
Insulation and Part L Compliance
A new pitched roof on a re-roof project is a common trigger for upgrading the roof insulation to meet current Building Regulations Part L standards.
Current Part L requirements for a pitched roof typically specify a U-value of 0.16 W/m²K or better on renovations affecting more than 25% of the roof area. This usually means:
- Cold roof build-up: insulation laid across the ceiling joists, with the loft space above unheated and cross-ventilated. Most common on re-roofs where the existing build-up is kept.
- Warm roof build-up: insulation between and above the rafters, with the roof space conditioned. Usual on loft conversions.
See Part L compliance for the current numbers and BS 5250 explained for the condensation control side.
Final Inspection
Before the scaffold comes down, a competent roofer does a full inspection:
- Every ridge and hip tile checked for mechanical fixing
- Every verge and eaves detail inspected
- All flashings checked for upstand, dressing, and pointing
- Valleys checked for lap, fall, and fixing
- Gutters run with water to check fall and discharge
- The loft space checked for visible daylight (none – anywhere)
- Debris cleared from gutters and hopper heads
Any issues are fixed before the scaffold comes down. Once the scaffold is down, every correction becomes much more expensive.
Warranty
A professional Sussex pitched roof install typically comes with:
- Workmanship warranty from the roofer – 10-25 years depending on the firm
- Manufacturer’s warranty on the tiles, slates, underlay, and fixings – usually 30+ years on modern clay or concrete tiles, 75-100 years on natural slate
- Insurance-backed guarantee if the roofer belongs to a scheme like NFRC’s Competent Roofer
Cornerstone Roofing is NFRC-accredited and a UK Roofing Awards 2025 finalist. That accreditation matters most in the rare event the firm is not around to honour its warranty – the NFRC scheme provides backup cover.
Getting a Quote That’s Worth Comparing
A pitched roof quote worth comparing to others should include:
- Named tile or slate product (not just “concrete tile” – the specific manufacturer and model)
- Specified underlay (named product and BS 5250 classification)
- Specified battens (BS 5534 Class A or B, 38 x 25mm minimum)
- BS 5534 wind zone and the fixing spec for that zone
- Dry ridge, dry verge, dry valley systems named
- Lead code and manufacturer for flashings
- Insulation spec and U-value achieved (Part L)
- Scaffold duration and cover
- Waste disposal included
- Clear warranty terms
Any quote missing these details is either hiding cost-cuts or is from a contractor who does not know the standards well enough to quote against them.
Book a Free Survey
If you are about to re-roof and want a quote that is genuinely comparable to others, book a free visit. We will survey your roof, give you a clear specification against BS 5534 and BS 5250, and lay out exactly what the job involves before the first tile comes off.