The Hotel Owner’s Hidden Vault Gamble: How Smart Drainage Design Turned Risk into Revenue

In the heart of the city, nestled beside a river, sits a historic building that had long concealed its potential behind locked vault doors. When a hotel developer acquired the site, their vision was clear: open up these unused underground vaults to maximise floor area, increase bedroom count, and start recouping their investment as swiftly as possible.

The original Roman baths in the centre of Bath, Somerset

However, as is often the case with historic properties, unlocking hidden value came with a set of complex engineering challenges.

The Challenge: Drainage Constraints in Shallow Vaults

The vaults, though structurally ideal for conversion into bedrooms, sat below the existing sewer connection. This meant traditional gravity drainage was unfeasible. Additionally, the building’s proximity to the river introduced high water tables and the presence of a culvert running along the front elevation, further complicating underground works.

A pumped drainage solution was required, but there were critical constraints:

• Shallow installation depth: Limited excavation depth due to structural and culvert risks.

•  Noise limitations: As bedrooms were directly adjacent to these units, all proposed pumps needed to undergo acoustician testing to ensure guest comfort.

•  Splash and pump noise: Both inflow splash noise and pump operating noise had to be minimised within a confined vaulted environment.

Collaborative Design Development

Working closely with the client and the consulting engineer, multiple solutions were put forward and tested for viability:

1. Shallow Packaged Pump Stations

   1. Units with minimal depth profile were specified to fit within the vault floor construction build-ups without compromising headroom or necessitating deeper excavations that could risk the culvert integrity.

2. Acoustic Performance Testing

   1. Each shortlisted pump unit underwent rigorous acoustic testing by a qualified acoustician. This assessed:

      1. Pump running noise levels under typical load conditions

      2. Inflow splash noise and how this transmitted through the vault structure

Design Adjustments to Reduce Noise Transmission

Solutions included:

1. Installing acoustic matting beneath pump chambers 

2. Specifying anti-vibration mounts for all pump motors

3. Introducing baffle plates and inflow deflectors to eliminate splash noise

Installation Considerations

Detailed construction sequencing was developed with the contractor to:

1. Avoid de-stabilising vault walls during pump pit installation

2. Coordinate with waterproofing specialists to maintain the integrity of the historic structure

3. Route discharge lines efficiently while maintaining accessibility for future maintenance

Delivering the Hotel Owner’s Vision

Through this highly collaborative approach, the team delivered a drainage solution that:

1. Kept installation depths to a minimum

2. Met stringent acoustic performance requirements

3. Integrated seamlessly within the confined historic vaults

This enabled the hotel developer to unlock valuable bedroom space and begin generating income significantly earlier than anticipated. By proactively addressing drainage and noise design challenges at the outset, the project team transformed redundant basement vaults into high-quality guest bedrooms – helping the owner realise their investment return while preserving the character of the historic building.