What Went Wrong? Drainage and Air Brick Violations in Landscape Projects
This expert witness review examines drainage and air brick violations in landscape projects, including damp proof course breaches, blocked ventilation, poor surface falls and incorrectly installed drainage channels.
This is the second in a series analysing landscape project failures as recorded by expert witnesses commissioned to produce court compliant statements for use by the court’s system.
All locations and company names have been redacted, and all images anonymised to avoid any conflict. All cases shown have been settled through proceedings.
Modus operandi – how the analyses are conducted;
In order to produce a series of inter-related articles, the same format will be used throughout.
All expert witness comments are made using either Industry Best Practice or British Standards where they apply when writing reports in the absence of any documentation or working practices mentioned as specification by a contractor.
DRAINAGE – Building Regulations 2010 Part H (Disposal and Waste Disposal)
H1 – Foul Water Drainage. H2 – Waste Water Treatment Systems. H3 – Rainwater Drainage, H4 – Building Near Faulty Drains.
Most of the work likely to fall under ‘landscaping’ will concern H3, although at times, more than one Part will apply.
Building Regulations 2012 (Part F – Ventilation (Health and Moisture)
Covers insufficient ventilation leading to rot in floor boards or damp causing black mould. This regulation covers air brick violations and blockages.
The five images below show typical site issues that have subject to claims by homeowners against contractors, usually following problems within the building.
All cases were subject to claims against the contractor, brought by insurance companies under household legal cover, under the Consumer Rights Act 2015.
One – Property in the West Country
The image shows the outside of an extension built onto a larger house. The rear garden had been covered in slate paving, in excess of eighty square metres. (None of the slabs had been laid using a bridge bond slurry, and the whole area had to be lifted and re-laid over a new bed.) Permeable grout had been used throughout, which reduced the potential volume of water traversing the site.
The contractor had included an ACO style drainage channel across the whole of the rear of the extension, installing it against the house walls.
Apart from violating the damp proof course by paving up to the d.p.c membrane, there was no outfall at either end of the channel to dispose of rainwater. The contractor decided to make a hole in the bottom of the gully, allowing all of the water to penetrate the ground adjacent to the extension.
This hole was the only outfall for the rear garden (except for dissipation through the permeable grout).
Two – Property in Berkshire
This is a new-build detached house, with new paving laid to the whole of the rear garden, total area approximately forty square metres.
The whole area of paving had been laid up to the damp proof course, with a narrow slot drain installed against the house wall.
The paving had been sawn around the air bricks as seen, with the cross fall on the paving directed towards the channel and house wall, allowing/directing rainwater into the building through the air brick, using it almost as a secondary drain, or additional outlet to supplement the slot drain.
Three – Property in Essex 2
This is a large new-build detached house, on a clay site. Porcelain paving had been laid across the rear garden, totaling in excess of four hundred square metres.
All of the paving had been laid on soft sand, with no slurry primer on the rear of the slabs. The jointing compound was single part resin (permeable) with no appreciative fall across the site, although with a slight fall towards the house and drainage channel.
The jointing compound had disintegrated and all of the joints had been colonised with moss.
A drainage channel had been installed against the whole of the rear of the house, at damp proof course level.
This caused issues with rainwater splash as seen against the house walls.
Crucially, as will be seen in the close-up photograph, all of the house air bricks – eighteen in total – had been completely covered with the drainage channel. (The air brick is just visible against the plastic cover in the centre of the image.)
Four – Property in Kent
This is the front driveway/car park to a Victorian house overlooking the sea, originally laid to tarmac (asphalt), which had become untidy and tired.
One year ago, the owners had the area of tarmac lifted and replaced with new (supposed to be SMA 6 wearing coat laid over an SMA 10 base coat. The complaint by the owner concerned the state of the tarmac as laid by the contractor, although other issues arose out of the site survey.
The contractor had laid a new drainage channel across the from of the house, leading to the corner of the building, where an existing downpipe discharged into the soil (there being no obvious drain)
They discovered a foul drain during their excavations, and decided to tap into the system, without using any proper sections.
At the end of the gulley, they stuffed a plastic cement bag to disguise the exit, which was directed into the foul drain, with no form of trapped bend to prevent odours from the drain installed.
In all four of these cases, all of the surfaces had to be lifted and re-laid on directions from the court and paid for by the contractor.
