Client
Marriotts Construction (Kier Group).
Location
Nevill Holt, Leicestershire.
Overview
Nevill Holt Hall is set in the Harborough District of Leicestershire, close to the Northamptonshire and Rutland borders. The sites elevated position gives fantastic views, overlooking the Welland Valley.
The Hall itself is a Grade 1 listed building, with the Great Hall dating back to the 13th Century. The project involved alterations and refurbishment of Grade II listed building, with major conservation issues, converting the Stable Block into a private theatre, swimming pool and leisure complex.
Problem
The alteration and refurbishment works included converting the 17th Century stable block into a theatre, with a new swimming pool being constructed along the eastern elevation of the stable block.
The stable block walls comprised rubble fill stonework built up off relatively shallow flagstone foundations. As excavations for the proposed swimming pool extended approximately 2 metres below the existing footings of the east elevation wall, underpinning of the existing foundation was necessary. This lead to concerns over partial collapse of the walls at low level during the underpinning works.
On addressing the problem of undermining the existing, shallow foundation, the main contractor still had the concern that excavating out for the new swimming pool could potentially affect the stability of the new deeper foundations.
TBL Solution
As an approved Helifix installer, we installed Helibeaming chords directly above the existing foundation, creating a load bearing beam in the rubble filled walling to distribute structural loads evenly. The Helibeaming helped provide the 17th century stonework with structural integrity and reduced the risk of collapse whilst phased underpinning works were carried out below.
We also used Helifix Cemties to cross pin the inner and outer leaves of the rubble filled wall in the ‘Helibeaming zone’ – again helping to consolidate and stabilise the rubble filled walling directly above the existing foundations.
Installation of test anchor to determine feasibility of achieving required 50kN working load per anchor in prevailing soils (combination of weathered Northampton Sands Formation and stiff grey silty clay from the Upper Lias series)
Installation of 19Nr MR1 galvanised duckbill ground anchors , each pulled up to the maximum holding capacity of 70kN/anchor and released down to a working load of 50kN/anchor.
Re-attendance to test installed anchors following excavation of the swimming pool.
Benefit
Using Helifix masonry reinforcement (Helibeaming and Cemties) we provided a cost effective means of consolidating and introducing structural integrity to the 17th century stonework, in a sympathetic manner to meet conservation approval.
By using the Helibeam system, a load bearing beam was created within the masonry, helping the stonework to span over phased underpinning excavations below.
In conjunction with Anchor Systmes, MR1 Duckbill ground anchors were successfully installed and tested to meet the specified working loads necessary to maintain safe working conditions whilst the excavation of the swimming pool was carried out.
Cost-effective repairs were completed quickly and efficiently, to meet an engineered specification, helping relieve concerns over the major conservation issues.
