Richard Tonkinson of Offsite Solutions offers some practical advice for specifying factory-built bathrooms.
Bathroom pods have driven innovation in traditional construction methods and are now widely used for student accommodation, hospitals, hotels and housing – from luxury apartments to social housing. The approach uses offsite manufacture to bring a range of benefits and improve the efficiency of construction.
The number of activities on site are radically reduced, resulting in significant programme savings, improvements in quality and waste reductions of up to 50 per cent.
On a large-scale, complex residential project, the programme saving can be as much as 20 weeks. This reduces the cost of site preliminaries, as well as waste removal and snagging. There is a faster return on investment for the client or earlier occupation, as well as much greater certainty of completion on time and to budget.
What are the different pod types?
Firstly, steel-framed pods – these offer ceramic tiled finishes and a high level of design flexibility. Applications include large-scale apartments, student residences and hotels.
Secondly, GRP pods are widely used for student accommodation, social housing and hospitals, requiring lower capital expenditure and being easy to maintain and clean. GRP pods we supply use a panellised system which creates vertical walls and 90 degree corners for improved aesthetics by avoiding tapered walls.
Concrete pods are less common, due to the higher loadings, but are seen occasionally in secure institutions such as prisons.
Innovations which have occurred in pod design include hybrid concrete/steel pods – using a concrete base and steel-framed walls, and seen in high-spec apartments.
Demountable GRP pods extend the application of pods to refurbishment with the use of a sectional structure. In commercial-to-residential conversions, and some new build projects, access may not be possible for fully assembled pods. Panel sizes of a demountable GRP pod are designed for easier access, for example, via the main entrance or facade openings. Up to 10 demountables can be installed in three days, with superior quality and the added benefit of having a single point of contact. Site-built bathrooms can take six- 12 weeks to complete requiring multiple trades and extensive site management.
Hybrid GRP pods allow an enhanced finish and improved aesthetics such as a ceramic-tiled feature wall and recesses. Appropriate applications would include Build to Rent schemes.
Lastly, floorless pods can be a useful option for projects where a continuous level floor finish is required throughout a building or for DDA compliance requiring floors with no threshold.
How are pods installed?
Factory-built bathrooms are delivered on a ‘supply-only’ basis, where the main contractor organises installation via the M&E contractor. The exception is demountable GRP pods, where we would undertake installation and assembly.
As many as 10 GRP pods can be installed in two hours – or six-eight steel-framed pods. It can take around 80 hours for a bathroom to be built on site requiring around 10-15 operations plus drying times. A pod can be manufactured in 14 hours in a factory, which means improved quality, mitigating defects and remedial works.
Key specification considerations
One of the first and most important specification considerations is early engagement – essential to achieve optimal efficiency by designing pods into the early stages of a construction project.
Next, consider access – accommodate pod installation in the build-up of walls and floors. Take account of access for delivery of the pods to site, particularly on constrained sites.
Look at economies of scale – standardised designs with minimal variations allow cost savings and time efficiencies to be achieved by using the repetition of the production process. A reputable manufacturer will have an extensive library of pod designs which architects can draw on. Pods can be bespoke but specifiers need to allow for modelling, prototyping, production engineering, machine programming, production line set up – and the manufacture of GRP moulds. To optimise efficiency, architects should rationalise the number of design types in size and shape, and variations, such as left and right hand versions, as far as possible.
Are you considering integrating pods with building services? Connections to services are made externally so access should be allowed for as part of the installation process. Connections from inside a pod are possible but are slower on site and affect quality. A good manufacturer will design the pods to facilitate installation,
using for example mechanically-fitted pan connectors and the option of pre-wired junction boxes to simplify electrics.
There are numerous other design aspects that should be taken into consideration when specifying bathroom pods. Depending on the project requirements and the size of the pod, the thickness of the pod base can be varied.
Natural materials such as marble and granite do not transport well and these finishes are not uniform so the typical tolerances that a pod manufacturer will work to may not be possible.
The building structure must clearly be designed to be able to support a pod, although the weight of a steel or GRP pod should be close to the weight of a site-constructed bathroom. With steel-framed pods there are eight point loads to take the weight of the pod and account for in the structural loadings.
And, finally, the floor slab should be flat and level to +/- 10 mm tolerance to ensure accurate installation.
Richard Tonkinson is executive director of bathroom pod manufacturer Offsite Solutions