Constructum Code carries out roofing and window work across London, most often within a larger project — an extension, a loft conversion or a refurbishment, where the roof is already open or the windows are coming out anyway. We also take these on in their own right where the scope warrants a fully managed project — a full re-roof, or window replacement covering a property rather than a single opening.
Interested in Roof Renovations and Windows?
Roofing
Pitched roofs
Slate, tile and shingle roofs recovered or repaired: damaged sections replaced, battens and underlay renewed where the covering comes off, the structure beneath repaired, and ridge, hips and verges reformed.
Ridge and verge tiles bedded only in mortar no longer meet BS 5534, which has required mechanical fixing since 2014. On a roof being recovered that means a dry ridge or dry verge system — and mortar failure is the usual reason an older roof starts shedding tiles along its edges.
Flat roofs
Renovation and replacement of flat roof coverings. Failures trace back to a membrane at the end of its life or water with nowhere to go, so falls are designed to clear rather than pond — standing water shortens the life of every system.
Metal roofs and coatings
Cleaning, sealing and recoating metal roofs, and waterproof coatings where a covering is sound but weathered. On the right substrate this is far cheaper than replacement; on the wrong one it postpones the problem, which is what the survey establishes.
Insulation, ventilation and rainwater
Insulation improved where the construction allows, and ventilation restored at eaves and ridge — most condensation problems in London lofts come from insulation laid over blocked eaves vents. Gutters, downpipes and rainwater goods are renewed at the same time, since a roof that sheds water into a failed gutter still soaks the wall below.
Roof windows and rooflights
Constructum Code is a certified VELUX installation partner and installs their roof window systems to the manufacturer’s specification, flashings and collars included — which is where roof window leaks almost always start, rather than in the unit. Rooflights are the least disruptive way to bring daylight into a top floor, and the simplest route to a usable room in a loft conversion.
Windows
Timber sash windows
New box sash windows in timber, including slim double-glazed units where the property and the planning position allow. On period housing the replacement has to match the original in section, glazing bar layout and opening method — which is where stock units fall down and made-to-match joinery earns its cost.
uPVC and aluminium
New windows and doors in uPVC and aluminium — casements, tilt-and-turn and larger glazed openings, fitted into new openings on extensions and lofts as well as replacing existing units. Constructum Code Ltd is Certass registered, so replacement glazing is self-certified under the competent person scheme rather than needing a building control application.
Conservation areas
Where an Article 4 direction applies or the property sits in a conservation area, replacements normally have to match the original in material, section and opening method. Worth establishing before anything is ordered — made-to-match joinery has a far longer lead time than a stock unit.
How we work
Survey first. The condition of the covering and the structure beneath, where water is getting in as opposed to where it shows, ventilation paths and scaffold access. On windows, the state of the frames and reveals, and any conservation or Article 4 restrictions.
Approvals. Like-for-like replacement generally needs no planning permission, though conservation areas and Article 4 directions change that. Replacement glazing is self-certified through Certass; other work goes through the building control route.
Costs agreed upfront. An itemised estimate before work begins. Where the covering comes off and reveals structural damage, it is priced, explained and agreed with you before the work proceeds.
One team, one programme. Scaffold, strip, structural repairs, underlay and battens, covering, ridge and verge systems, flashings, then rainwater goods — the same site team and project manager throughout.
Minimal disruption. Roof work is noisy, and windows mean openings in the building for part of a day. Both are sequenced so the property stays weathertight overnight and secure throughout.
Guaranteed on completion. A 10-year warranty on the structural work, and the manufacturer guarantees on coverings, roof windows and glazing.
Fully insured and accredited. £10m employers’ liability, £5m public liability and £1m professional indemnity cover. Constructum Code Ltd is a TrustMark registered firm, a certified VELUX installation partner, and registered with Certass and FairTrades.
What it costs
Priced by the property rather than by a rate, because the same job on two houses can differ by a factor of two.
- Access and scaffold. Scaffolding usually adds around £900 plus VAT, and more on a terrace with no side access or a roof over a back addition.
- What is found once the covering is off. Rotten battens, failed lintels and damaged rafters are common on roofs that have been leaking.
- Whether materials can be salvaged. Reclaimed slate and matching tiles cost more than new, and on a conservation street they are often the only option.
- Roof size, pitch and complexity. Valleys, hips, dormers, chimneys and parapets each add detailing.
- Number and type of windows. Made-to-match joinery and a stock uPVC casement are different orders of cost and lead time.
- Whether it runs within a wider project. With the scaffold already up for an extension or a loft, this work costs considerably less.
We price after the survey, so the estimate reflects what is actually there.
Common questions
Will you take on my roofing or window job?
It comes down to size rather than type. A full re-roof, or windows across a whole property, we take on as a project in its own right. A single window or a handful of slipped tiles is better suited to a local roofer or glazier working at that scale, and we will tell you so rather than quote for it. Where the work sits alongside an extension, loft conversion or refurbishment, there is no minimum — it forms part of the project.
Do I need planning permission to replace my windows?
Usually not, if the replacements match what is there. In a conservation area, or where an Article 4 direction applies, they generally have to match in material, section and opening method, and timber to uPVC is often refused. Worth establishing before anything is ordered.
Do replacement windows need building control approval?
They have to meet current Building Regulations — thermal performance, safety glazing, escape from habitable rooms and ventilation. Because we are Certass registered, the work is self-certified under the competent person scheme and a certificate is issued on completion. Note that replacement windows now generally need trickle ventilators, which older ones often lacked.
Should the roof be repaired or recovered?
Isolated slipped tiles, a failed flashing or a blocked valley are repairs. Widespread nail fatigue, failed underlay or mortar-bedded ridges lifting along the whole run point to a covering at the end of its life, where repeated repairs cost more over five years than recovering once. The survey establishes which, and we say so either way.
Why does my loft get condensation after new insulation?
Almost always because insulation was laid into the eaves and blocked the ventilation path. A cold roof relies on air moving from eaves to ridge to carry moisture out; when that stops, it condenses on the underside of the roof and runs back onto the insulation. Straightforward to correct with ventilation trays and, where needed, extra ridge or tile vents.
