A roof over one house has one owner and one set of questions. A roof over a block of flats has several. The freeholder wants to know the condition of the asset, the managing agent wants a list of jobs in a sensible order, the leaseholder on the top floor wants to know why a ceiling has stained, and everyone paying into the service charge wants to see where the money goes. A survey of a multi-unit building has to answer all of them from one visit and one report. This guide explains how that survey is scoped, which parts of the building it covers, how access is organised when a roof is shared by many households, and what the written report should contain so it can be used for a single repair, a planned programme or a conversation with residents. The principles apply to purpose-built blocks, converted Victorian and Georgian houses, and mixed commercial and residential buildings in Bath and the 30 road miles around it.
Why a block needs a different kind of survey
On a single house, a leak in the back bedroom usually points to the roof directly above it. In a block, a leak can wander. Water slides down a rafter, creeps behind a lead upstand at the parapet, or soaks down a wall for two floors before a brown ring appears on somebody's ceiling. The flat that reports the damage is often not the flat under the fault, so the survey has to follow the water back to its source rather than stop at the first sign.
A block also carries more roof types than a house does. One building might have a pitched main roof in natural slate, a flat roof over a rear extension, a small roof over a lift motor room, a lead-lined gutter behind the front parapet and a lean-to over a bin store. Every one of them wears out differently, on its own timetable, and every one wants a different inspection method. A survey that treats the whole building as one roof will miss the one that matters.
The third difference is the number of people who depend on the answer. A repair report for a house is read by the owner. A report for a block may be read by a freeholder, a managing agent, a surveyor acting for a buyer of the freehold, a residents' company and a leaseholder who wants to know whether a charge is fair. It therefore has to be clear without a roofer standing beside it.
Before we go up, it helps if the managing agent can send any log of leak reports, with dates and flat numbers, along with earlier repair invoices and a plan of the building. A pattern of reports from the same stack of flats tells us where to look first, and it saves time on the roof.
Scoping the survey: inclusions and exclusions
The scope is agreed before the visit, in writing, so the report matches what the client expected. The first decision is the extent: the whole roof, one elevation, or one problem area such as a flat roof that keeps leaking. The second is the depth: a visual survey from the roof and from ground level, or a survey that also opens up hatches and looks into communal roof spaces.
The leases decide which parts belong to the freeholder and which to a leaseholder, so we ask the managing agent to confirm the boundary before we start. In most blocks the roof structure, coverings, gutters, rainwater pipes and chimneys are communal, while a roof terrace or a rooflight serving a single flat may be treated differently. Ownership of each part is a legal question for a solicitor or the managing agent. What we can do is record each part so that whichever way the lease reads, the evidence is there.
| Part of the building | What the survey records |
|---|---|
| Roof coverings | Type, condition, slipped or cracked units, moss and signs of repairs |
| Ridges, hips and verges | Bedding, fixings, cracks and displaced pieces |
| Gutters and rainwater pipes | Blockage, joints, falls, brackets and staining on the wall below |
| Parapets and abutments | Coping stones, pointing, lead dressings and flashings |
| Flat roofs | Membrane, ponding, outlets, upstands and edge trims |
| Chimneys and rooflights | Pointing, flaunching, pots, seals and flashings |
Anything outside the scope is listed as not inspected, so the report never leaves a reader guessing.
Getting onto the roof of a shared building
Access is the part of a block survey that takes the most organising. A house has one front door and one owner who can say yes. A block has residents who need notice, keys held by the managing agent, a roof hatch that may be inside a locked cupboard and a flat roof reached only through a top-floor flat.
We ask for the access route in advance. The options, from simplest to most involved, are an internal hatch to the roof, an external fixed ladder, a loft or stair-top door, a tower scaffold at one elevation, and full scaffold to a number of elevations. A good survey uses the lightest method that shows the roof properly. Where a tower or ladder is not safe or not justified, a pole camera can look along a gutter or over a parapet from below, and a drone can photograph slopes that cannot be reached. Rules for flying one over a block are covered in our guide to drone roof survey rules.
Residents should be told when we will be on site and what we will be doing, preferably by a note from the managing agent a few days ahead. Most of the survey happens outside, but if we need to look at a ceiling stain from inside a flat, we arrange that visit with the occupier, and we leave the flat as we found it.
Edges matter on a block. Parapets, roof lights without guards and flat roofs without an edge protection rail all have to be treated as hazards before anyone walks on them. We plan the work at height before the visit, and where a roof cannot be walked safely, the survey is done from a safer position and the report says so.
Reading the roof zone by zone
On a block we split the roof into zones, usually by elevation or by stair core, and number them on a plan. Every photograph and every finding is tied to a zone. That sounds fussy until a managing agent has to ask a contractor to price the work to "the rear flat roof over flats 7 to 9" and the contractor can see exactly which area is meant.
Pitched slopes
On a pitched roof we look at the covering as a whole, then at its details. The covering is scanned for slipped or cracked slates and tiles, moss holding water against the surface, and any dip between rafters. Clean, bright patches usually mark earlier repairs. The ridge, hips and verge are checked for loose or cracked pieces. Under BS 5534:2014 a bed of mortar can no longer be relied on by itself to keep ridge, hip and verge pieces in place, so older work is checked for a mechanical fixing.
Flat areas
On a flat roof we look for ponding, which is standing water after rain and a sign that the surface has lost its fall. BS 6229:2018 guidance, as quoted by one manufacturer, is that the recommended minimum fall is 1:80, with 1:40 as the design target. We also check blisters, splits at seams, lifted upstands and blocked outlets.
Gutters and junctions
Two terms recur in block surveys. The parapet gutter sits behind a low wall along the eaves and is lined with lead. The box gutter is its cousin, a lined trough sunk between two slopes. Both carry a lot of water from a large area, and in a block they often serve many flats. Where metal is dressed over a joint to throw water off, the strip is called a flashing, and we look for lifting, splits and open laps in each one.
What a useful report contains
A report for a block is a working document. It should let a managing agent decide what to do, brief a contractor and explain the position to leaseholders without further site visits. Ours is built around five parts.
- A roof plan with zones. A simple annotated sketch marks each pitched and flat area, the hatches and the places photographed.
- A photo schedule. Each picture is of your own roof, numbered, labelled with its zone and captioned with what it shows.
- Findings by zone. Each zone gets a short description of its condition, the cause of any defect where we can identify it and what we could not see.
- Ranked actions. Work is split into what should be made safe or watertight now, what should be done in the near term and what can be planned over a longer period.
- A scope for pricing. The recommended work is described so that it can be priced like for like.
On cost, MyBuilder's roof inspection guide (2026) gives typical UK ranges of £150 to £500 for inspections, with a standard inspection at £150 to £250. Those are house-sized figures and a block takes longer because of its size and access. The price for a block depends on how many roofs, how many elevations and how the roof is reached, so we set it after looking at the building. Your fixed quote follows the survey.
From survey to repair, programme or replacement
The survey usually points to one of three outcomes. The first is a targeted repair: relining a split section of parapet gutter, replacing a failed outlet on a flat roof or refixing a run of ridge. If repair works, that is what we recommend, and the report prices it that way.
The second is a planned programme. A block with a good roof at one end and a tired one at the other does not need to be re-roofed in a single operation. Work can be phased by elevation or by stair core, with the most exposed or most leaking areas first. A phased plan needs to be consistent in materials so that repaired and untouched areas still look like one roof, and a slate roof is patched with slate, never with a look-alike.
The third is full replacement, which brings Building Regulations into it. Planning Portal guidance says re-covering normally needs no approval only while the work touches under 25 per cent of the building envelope, and also under 50 per cent of the roof itself. A full re-roof of a block sails past both limits, so approval applies, and an upgrade to the roof's insulation may be part of it. We explain the consent side and handle the Building Regulations notification where work is notifiable. A new covering 15 per cent heavier or more triggers approval and a structural check regardless.
Plenty of Bath blocks are listed or stand in the conservation area, and the city as a whole is inscribed as a World Heritage Site. For those buildings, read our guide to surveying listed and historic roofs. Anyone buying a block or a building with flats above shops can use the same methods as a pre-purchase roof survey. Our general approach to inspections lives on our roof inspections page. For a block, it helps to gather the lease clauses on roof repair and any previous survey reports before the visit, so the findings can be matched to who pays.