Usable space above a waterproofed roof
The terrace finish is only as reliable as the roof beneath it
A roof terrace or balcony has to perform as both a roof and an external space. Water must move below or around paving and decking, through suitable falls and outlets, while thresholds, parapets, balustrades, rooflights and wall junctions remain weather-tight.
ER Group London plans the roofing scope around the complete build-up rather than treating the visible finish as a separate package. Existing construction, waterproofing, drainage, insulation where relevant, perimeter details and the intended walking surface all influence the final arrangement.
Where structural design, guarding, planning or other professional information is required, that information should be established through the appropriate project team and coordinated with the agreed roofing work.
Typical project contexts
Where a coordinated roof-terrace approach matters
The service is intended for residential projects where waterproofing and the usable surface have to be considered together.
Leaking Terraces Above Rooms
Water ingress where outlets, thresholds, parapets, penetrations or the main waterproofing need to be assessed as connected details.
Roof Terrace Conversions
Existing roof areas being adapted for residential terrace use as part of an agreed, professionally informed project scope.
Balcony & Terrace Renewal
Replacement where waterproofing, drainage and exposed edge details have deteriorated together.
Paving & Decking Build-ups
Walking surfaces that need to drain freely, protect the waterproofing and allow access to important roof details.
Period & Sensitive Homes
Projects where thresholds, parapets, leadwork and visible finishes need to sit carefully with the existing building.
Architect-Led Projects
Roofscape work coordinated with drawings, structural information and the wider residential programme.
Design & assessment
Resolve the roof before fixing the finish
The build-up should be planned from the supporting construction and water path upwards.
Supporting construction
Confirm what the waterproofing is built on
Deck condition, previous layers, movement, concealed moisture and any project-specific structural information can affect how the terrace roof is rebuilt or repaired.
- Existing deck and build-up
- Movement and concealed condition
- Professional information where required
Falls & drainage
Give water a clear route beneath the finished surface
Falls, outlets, channels and overflow routes need to remain effective after paving, pedestals or decking are installed. The finished surface should not obstruct the drainage path or prevent routine access to outlets.
- Falls and low points
- Outlets and overflow routes
- Access for inspection and cleaning
Thresholds & upstands
Coordinate door openings, parapets and finished levels
Door thresholds, walls, parapets and rooflights can constrain available waterproofing heights. The complete junction should be resolved with drainage and adjacent finishes before the build-up is fixed.
- Door and rooflight thresholds
- Parapet and wall upstands
- Transitions to adjoining finishes
Balustrades & penetrations
Plan attachments before they meet the waterproofing
Balustrades, screens, services and other attachments should be coordinated so their support and waterproofing details work together without avoidable vulnerable penetrations.
- Guarding interfaces
- Service penetrations
- Edge and coping details
Surface finishes
Support paving or decking without trapping water
The final walking surface should protect the waterproofing, allow drainage and remain removable where access to outlets or inspection points is required.
- Paving or decking support
- Drainage below the finish
- Inspection access
Repair or renewal
Choose the intervention after the connected details are understood
A visible leak does not by itself determine whether the right answer is a local repair or a complete terrace rebuild.
Local Repair
Appropriate where a specific defect can be identified and the surrounding waterproofing, drainage and interfaces remain serviceable.
Partial Renewal
Suitable where a defined area can be reconstructed without leaving vulnerable transitions to adjoining work.
Complete Terrace Renewal
More appropriate where waterproofing, falls, thresholds or several connected details have deteriorated together.
Leak investigation
Trace water through the whole terrace detail
Water can travel beneath finishes before it becomes visible internally, so the apparent leak position may not identify the actual entry point.
Leak investigation
Trace water through the whole terrace detail
Investigation may need selected finishes to be lifted or parts of the build-up opened in a controlled way. The scope should record what could be inspected, what remains concealed and how exposed areas will be protected.
- Main waterproofing
- Thresholds, outlets and parapets
- Balustrade and wall interfaces
Verified roof terrace project
Fulham: pitched roof converted into a usable terrace
At Fulham, ER Group London converted an inaccessible pitched roof area into a flat-roof terrace with direct kitchen access, glazed guarding and a raised iDecking finish.
- Roof-area conversion
- Direct kitchen access
- Glazed guarding and raised iDecking finish
Verified roof terrace project
Paddington: insulated EPDM roof renewed beneath a terrace finish
At Paddington, a leaking asphalt roof was renewed with a documented insulated build-up, EPDM membrane, walk-on glass rooflights and a decked terrace finish.
- Insulated roof build-up
- EPDM membrane
- Walk-on glass rooflights and decked finish
Delivery & protection
Protect the property and the completed waterproofing
Opening-up, temporary protection, drainage and later finishes should be sequenced around the rooms and building fabric below.
Occupied Areas Protected
Opening-up and weather exposure are planned around the sensitivity of internal rooms and finishes.
Adjoining Fabric Considered
Doors, facades, masonry and internal floor levels are coordinated with the roofing detail.
Drainage Kept Clear
Outlets and water paths should remain protected and accessible while work is in progress.
Later Finishes Coordinated
Paving, decking and other subsequent work should be installed without damaging or obscuring critical waterproofing details.
Inspection Access Retained
Outlets, channels and agreed inspection points should remain accessible in the completed arrangement.
Handover Information
Relevant roof build-up, access and maintenance information can be recorded at completion.
Roof terrace FAQs
Questions About Roof Terraces & Balconies
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Water can enter at thresholds, outlets, parapets, penetrations or the waterproofing itself and then travel beneath the surface finish before it appears inside.
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Sometimes, but only where the finish can be removed or retained without preventing the required inspection, repair and drainage access.
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They are fundamental. The roof has to move water towards suitable outlets while the completed terrace finish continues to allow that drainage route to work.
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No. Available waterproofing height, drainage, door construction and the surrounding build-up have to be assessed for the individual project.
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The support and waterproofing detail must be coordinated for the project. Avoidable penetrations should not be introduced without a properly resolved junction.
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Some do. The requirement depends on the property and proposed work. Where professional design or approvals are needed, that information should be established before the roofing scope is finalised.
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The selected support and finish arrangement should protect the waterproofing, allow drainage and preserve access to outlets and agreed inspection points.
Plan the complete terrace build-up
Discuss a Roof Terrace or Balcony Project
Send the property address, photographs, information about the rooms below and any drawings or details already available for the existing roof, thresholds, drainage, balustrades and surface finish.