Cambridge Roofers carries out roof repairs in Grantchester, using the right materials for each job so the repair lasts and the roof performs as it should.
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When a roof develops a problem, the material used to fix it is just as important as the skill of the person doing the work. Using the wrong mortar mix, a cheaper grade of lead, or a poorly matched replacement tile can mean the repair fails within a season or two. This page sets out the main materials used in pitched and flat roof repairs, their honest advantages and drawbacks, and what you should ask about before any work starts.
Roof repair is a broad term. At one end it means replacing a single cracked tile; at the other it means recovering an entire flat roof section or repointing a chimney from top to bottom. The most frequent repair jobs on residential properties fall into a handful of categories.
Each of these involves different materials with different properties, costs and expected lifespans. Understanding the options helps you have an informed conversation with any roofer and make sensible decisions about spending.
When a tile or slate needs replacing, the best outcome is an exact or near-exact match to what is already on the roof. Mismatched tiles are visually obvious and, on an older property, can affect a planning condition or conservation area requirement. They can also create drainage problems if the profile is significantly different from the surrounding tiles.
Clay tiles are long-lasting, often 60 to 100 years or more, and they retain colour well. Reclaimed clay tiles are widely available and are often the right choice when matching older roofs. The drawback is cost: reclaimed handmade clay tiles are more expensive than concrete alternatives, and finding a close match in profile and colour takes time.
Concrete tiles are cheaper and readily available in a wide range of profiles. They are heavier than clay and can cause problems on roofs not originally designed for them, but like-for-like concrete replacements on existing concrete-tiled roofs are straightforward. Concrete tiles fade over time, so a new tile on an older roof will stand out more than a reclaimed clay tile would on a clay roof.
Natural slate is still widely used and, when properly fixed, is among the most durable roofing materials available. Welsh slate is generally considered the superior product for longevity and appearance but is considerably more expensive. Spanish slate is a practical and cost-effective alternative on most properties. The key with slate replacement is the fixing method: nailed directly to the batten or hung on copper or stainless steel hooks, and the decision about which to use depends on the pitch and exposure of the roof. Avoid galvanised fixings on slate, as they corrode faster than the slate itself.
Ridge and hip tiles sit at exposed positions on the roof and are fixed by bedding them on a mortar mix and pointing the joints. When this mortar fails - which it eventually will through weathering and thermal movement - the tiles can lift in wind and water enters at the joints.
Traditional sand and cement mortar is still widely used and works well when mixed and applied correctly. The mix ratio matters: too much cement creates a rigid bed that cracks as the roof moves with temperature changes; too little and it weathers quickly. A good roofer will use a mix in the region of 3:1 or 4:1 sand to cement, with a plasticiser added for workability. The repair also involves cleaning off the old mortar fully before re-bedding, not just pointing over the top of what is already there.
Dry-fix ridge systems use mechanical fixings and a continuous ventilation strip rather than mortar. The advantage is that there is no mortar to crack or wash out, so the fixing point lasts much longer. Dry-fix systems also allow a small degree of roof movement without opening up gaps. The disadvantage is upfront cost: dry fix is more expensive to install than a mortar bed, and on a conservation area property the appearance may not be acceptable. For a full ridge re-point or re-bed, dry fix is often worth the extra cost on a newer roof that is otherwise in good condition. On a 1960s or 1970s roof where other work may be needed in coming years, it is a conversation worth having with your roofer before committing.
Lead is the standard material for sealing the junctions between a roof covering and any vertical surface - chimneys, walls, dormers, rooflights and soil pipes. Properly dressed and fixed lead, using code 3 or code 4 sheet depending on the application, will last 50 to 70 years. What goes wrong is usually one of three things: the lead has been cut too short, poorly lapped, or pointed in with mortar rather than being chased into the masonry.
Lead needs to be dressed into a chase cut into the mortar joint - typically 25mm or more - and then held with lead wedges and pointed with a proprietary sealant or mortar. If a roofer has simply pressed lead against the wall and filled the top with silicone, that will last a few years at best. Silicone does not bond reliably to lead over the long term and cracks away from masonry as the building moves.
Lead also needs to be cut into manageable lengths (generally no more than 1.5 metres for step flashings) to allow for thermal expansion. One-piece flashings that run the full length of a chimney or wall will buckle and crack as they heat and cool through the seasons.
The alternative to lead in some applications is aluminium flashing tape or mortar-based systems, but these are short-term measures and should not be used where a lasting repair is the goal. For chimneys and dormers on residential roofs, lead is still the correct and most durable material.
Flat roofs on extensions, bay roofs, garage roofs and porch canopies need repairing or recovering more often than pitched roofs because they are more vulnerable to ponding water and temperature movement. The two materials most commonly used for flat roof repairs and recovers are mineral felt and EPDM rubber.
Mineral felt is the traditional and lower-cost option. A three-layer torch-on felt system, where each layer is heat-bonded to the one below, is significantly more durable than the older cold-applied felt systems found on many extension roofs. Torch-on felt typically has a lifespan of 15 to 25 years if installed correctly on a sound deck. The disadvantage is that felt systems can crack at laps and along upstands where they are subjected to repeated movement, and a poorly installed system fails earlier than that. Cost for a felt recover on a small flat roof (say 15 to 25 square metres) typically runs from £800 to £1,800 depending on the area and condition of the deck below.
EPDM rubber has become the preferred choice for flat roof repairs on residential properties in recent years. It is a single-ply membrane, fully adhered to the deck with contact adhesive, that handles thermal movement much better than felt. It does not crack along fold lines and, when correctly installed with properly sealed seams and upstands, typically lasts 30 to 50 years. EPDM costs more to supply and install than felt but tends to work out better value over the roof's life. For a flat roof of 15 to 25 square metres, an EPDM recover typically costs in the region of £1,200 to £2,500. The price per square metre for EPDM generally falls between £50 and £100, depending on access, deck preparation and the size of the area.
A repair to an existing EPDM membrane - sealing a lifted seam or a puncture - is straightforward with the correct EPDM primer and seam tape, and costs far less than a full recover. The catch is that the rest of the membrane must be in sound condition for a patch repair to be worthwhile.
The honest answer to whether a repair or full replacement is better value depends on the age and overall condition of the roof, not just the defect in front of you. A roof that is 10 or 15 years into a 60-year life and has developed an isolated problem is almost always worth repairing. A roof where multiple areas are failing, where the felt underlay has perished, or where the timbers have been wet for a long time is a different situation.
Ask any roofer to explain what they found during their inspection, what is in good condition and what is not, and why they are recommending repair or replacement. If they cannot answer those questions clearly, that is worth noting before you agree to anything.
As well as Grantchester, we carry out roof repairs across Cambridge and nearby places. If you are in a village neighbouring Grantchester and are not sure whether we cover your area, call us and we will confirm.
As well as repairs, we carry out full roof replacements, chimney rebuilds, flat roof recovers, lead flashing installation and gutter work. If your property needs something other than a repair, call us and describe what you are dealing with - we will point you in the right direction.
If you are unsure which material is right for your repair, or whether a repair is the right answer at all, call Cambridge Roofers. We will assess the roof, explain what we find and give you honest advice on the materials and options before you commit to any work.
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Call any time. Calls are answered day and night and passed straight to our roofers.
