Rainwater goods on new build housing schemes get treated as a small package hanging off the roofing programme. In practice, the gutters, downpipes and outlets they connect to are one of the more consistent sources of post-handover defect claims and one of the areas where poor coordination between trades produces visible failures within the first year.
The specific coordination issues on rainwater goods
The specific issues are well known. Fall on the gutter run insufficient to reach the downpipe. Downpipes discharging where they should not because the drainage installer laid the connection somewhere different. Outlets sized inadequately for the roof catchment area. Fixings too widely spaced for the wind exposure at that location. Each is a small install detail. Each produces water where it should not be.
The coordination challenge is that rainwater goods sit between three trades. The roofing contractor installs the gutter and outlet. The drainage contractor installs the below-ground connection. The building envelope contractor manages the wall interface where the downpipe fixes. Where the three do not coordinate at design stage, the interface produces problems that emerge as leaks in year one.
Globe Roofing's pre-start coordination on new build housing includes rainwater goods as a specific item rather than assuming it falls out of the roofing scope automatically. Falls are confirmed against the design. Downpipe positions are checked against the drainage connections. Outlet sizing is verified against the roof catchment. Wall fixing positions are agreed with the envelope contractor before either trade starts.
Managing the interface when packages are split
On schemes where the roofing and drainage packages are delivered by different contractors, this coordination has to be actively managed by the principal contractor or the developer. On Globe Group schemes where GCE is delivering the below-ground drainage, the coordination happens internally and the developer does not have to convene it.
There is a specific fall calculation worth being clear about. Standard practice on new build housing is a minimum of 1:600 fall on horizontal gutter runs. Where the run is long, the total drop needs to be accommodated within the gutter depth without the downstream end sitting below the tile edge. On roofs with long straight runs, this calculation is not always trivial and can require multiple outlets rather than a single one.
Fixing pattern for gutters is another item that gets underspecified. Standard fascia bracket spacing works for moderate exposure but is inadequate for higher exposure zones. Where the fixings are too widely spaced, wind uplift or snow load causes the gutter to sag or detach. The failure typically appears in the first significant weather event after handover.
What QSs and developers should be checking at tender
For QSs pricing rainwater goods on housing schemes, the practical questions are about the fall calculation, the outlet count, the fixing density, and the coordination with the drainage installer. A contractor who has thought through these produces a different tender to one who has priced generically. The difference typically emerges as defect claim rate across the warranty period.
There is also a specific consideration around leaf and debris on schemes near trees. Where the property will experience heavy leaf fall, standard gutters silt up rapidly and need cleaning or dedicated leaf guards. Specifying this at design rather than leaving it to the homeowner produces better long-term performance and fewer maintenance-related issues.
For developers, the practical implication is that rainwater goods deserve attention at design stage rather than being treated as a low-value adjunct to the roofing package. The cost of getting it right is small. The cost of the warranty claims that follow when it is wrong is meaningful.
Talk to Globe Roofing
To discuss rainwater goods coordination on your scheme on your scheme, contact Globe Roofing on 01223 890727 or email enquiries@theglobegroup.co.uk.
