A rooflight is fitted into a tiled roof in eight stages: mark the opening from inside, strip the tiles back in whole courses, fix trimmers and cut the rafter, form the underlay into a collar, set the frame at the manufacturer’s depth relative to the batten, fit the apron, soakers and head flashing, re-tile up to the metalwork, then insulate and line the reveals inside. The roof is watertight the same day.
That is the sequence a competent crew follows on a plain tile, concrete interlocking or clay pantile roof anywhere in Ipswich or Suffolk. What varies is the flashing kit and how much of the tile has to be cut. The order does not vary, and the order is what keeps water out.
The sequence in full
- Set out from inside. The opening is marked in the loft against the actual rafters, then transferred through the roof with fixings at the corners. Working from outside alone means guessing where the timbers are, and a 30mm error at this stage becomes a rafter cut you did not need.
- Strip the covering back. Tiles or slates are lifted in whole courses across a width wider than the window, because the flashing needs clean tiles either side to sit on. They are stacked for reuse. Nails are drawn rather than tiles snapped off. On a Suffolk pantile roof, breakages get replaced with reclaimed stock, which is one reason those jobs are surveyed properly first.
- Cut the battens. Battens are cut back only as far as the opening plus the frame clearance, and the cut ends are supported. Battens carry the tile load, so cutting more than needed means re-battening a larger area later.
- Fix trimmers, then cut the rafter. Horizontal trimmers of the same section as the rafters go in top and bottom, fixed into the full depth of the rafters either side. Only once those are in does the rafter get cut through. Doing it the other way round means the roof takes the load in the wrong order for the ten minutes that matter. Where two or more rafters are cut, or the roof is trussed, this stage waits for a structural engineer’s design. Trussed rafters are engineered as complete units and are never cut on assumption.
- Square and pack the opening. An old roof settles. Rafters bow, ridges sag, and a 130-year-old opening is rarely square. The opening is packed and trued to the frame rather than the frame forced into the roof, otherwise the sash binds on one corner and the flashing sits unevenly.
- Form the underlay collar. The roofing underlay below the battens is the second line of defence. It is cut to a pattern, dressed into the opening, taken up the outside of the frame position and, below the window, dressed out over the underlay of the course beneath so any water that gets past the tiles is discharged back onto the drainage plane. A membrane slashed with a knife and left flapping is the single most common hidden defect in this trade.
- Set the frame. The frame drops onto its brackets at the depth the manufacturer specifies relative to the top of the tile batten. That one dimension is what makes the flashing geometry work. Set too high and the head flashing bridges the course above instead of sitting down into it, and water runs under. It is checked square across both diagonals before final fixing.
- Flash it. Apron dressed down over the course below. Side sections and soakers interleaved with each course as the tiles go back up the sides. Head flashing tucked under the course above and dressed into its profile, with the drainage gutter behind it clear. At the end of this stage the roof is weathertight, and that is the point at which we stop for the day if we stop at all.
- Re-tile. Tiles are cut to fit around the metalwork, not the other way round. Cut tiles get clipped or nailed rather than relying on their own weight. Mortar is a bedding and a finish here, never the weathering.
- Insulate and line. Inside, a preformed insulation collar or cut rigid board closes the void around the frame, the vapour control layer is taped to the frame on the warm side, and the reveals are formed splayed, vertical at the head and horizontal at the sill. Then plasterboard, skim and trims.
This is a description, not an instruction. We are setting out what will happen at your house so you can judge a quote and recognise a corner being cut. Nothing on this page is an invitation to get onto a roof. Rooflight work needs edge protection, a scaffold or tower, and two people.
How the tile type changes the job
The covering decides the flashing kit, and the kit cannot be swapped afterwards without taking the unit back out.
| Covering | Flashing kit | Extra work on site |
|---|---|---|
| Natural or fibre cement slate | Flat profile | Slates cut and hook-fixed or nailed, short soakers, neatest finish |
| Clay or concrete plain tile | Flat profile | Double lap maintained through the soakers, longer soakers |
| Interlocking concrete tile | Standard profiled | Soakers dressed over the interlock rib, cut tiles clipped |
| Clay pantile | High profile, deep-pressed apron | Apron dressed into the trough, no mortar filling the rolls |
| Handmade Suffolk pantile | High profile plus lead | Lead soakers formed individually to each tile, slower, costs more |
The failure we get called to most often on tiled roofs is a head flashing bridging the course above rather than dressing into it, followed closely by a flat kit fitted to a deep-profile pantile with the voids under the rolls filled with mortar. That mortar cracks within about three winters. Neither of those is a product fault. Both are decisions made in the first hour on site. Where a unit has already reached that stage, we replace it rather than patch around it, because patching a wrongly set frame just moves the leak.
What it means for your house
On the Victorian and Edwardian slate terraces around central Ipswich the work is quick and the finish is very flat, though conservation area status frequently dictates the unit pattern. On the 1960s to 1980s interlocking concrete at Chantry, Rushmere St Andrew and Kesgrave it is the most straightforward version of this job, and it is the bulk of local loft conversion work. Across the villages, clay pantile adds a day and a deep-profile kit. On new-build roofs at Grange Farm, Sproughton and Martlesham the structure is trussed, so the size question gets settled before anything else.
A single rooflight into an existing tiled roof with one rafter trimmed is generally one to two days, and we cover that in more detail on how long it takes to fit a pitched roof rooflight. If cutting a rafter is something you would rather avoid entirely, there are sizes that fit between standard rafter centres with no structural work at all. The full picture of rafters, trimmers and when an engineer is needed sits on our structural opening page, and the flashing kits are covered properly on our flashing kit installation page. The parent service page, pitched roof skylight installation, covers pricing and the whole scope.
Tell us the covering, whether it is a new opening or a replacement, and where the property is. We survey from inside the loft, confirm the rafter positions and the tile profile, and give you one written fixed price with the flashing kit and both collars itemised. Every installation carries a 10-year workmanship guarantee. Request a fixed quote.
Thinking about this job? We survey across Ipswich, Suffolk and north Essex and give you a fixed price before any work starts, with a 10-year workmanship guarantee.