The Existing Roof

The existing roof was finished with Redland Stonewold concrete interlocking tiles which were to be removed and replaced with Redland Cambrian reconstituted slates on a new breathable underlay and battens, with all associated lead valleys, flashings, etc.

This work was to be carried out over a live and fully operational community hospital.


The obvious challenge whilst undertaking this project was the issue of maintaining full weather protection over a live hospital whilst renewing the entire roof. Working closely with the hospital staff, each ward was temporarily vacated to permit roofing works overhead.

However, due to the workload of the hospital, the timeframes available for each area were very restrictive. We were therefore required to strip the existing tiles, felt and batten to areas of up to 900m2, allow any remedial carpentry work, then re-felt, batten and lay new Redland Cambrian slates, with all appropriate detailing, to produce a fully weather and waterproof section for immediate re-occupation.

Typically, this whole process was turned around in 10 working days. We actually managed to reduce the total re-roofing programme period of 28 weeks by over 14%, to 24 weeks.

The actual roofing work was complicated by a roof re-design that included a mid-height step running across the outside of all five wings, which reduced the roof pitch on the upper roof sections. This also required the renewal of lead flashings along the full lengths of the steps, up to 90 metres in length.

In addition to this, the large glazed areas interspersed in the pitched roof areas also required renewal. This obviously complicated the re-roofing process as not only did we have to accommodate a further trade, but we had to ensure that the whole area remained weather-tight before, during and after the glazing processes.

The Environment

The environmental impact of the project was mitigated by two main points:

1. The Redland Cambrian slates which were used were manufactured in Rassau, near Ebbw Vale, which is just 30 miles away from the site. This is obviously more efficient than bringing slates from elsewhere in the UK (e.g. North Wales which is around 120 miles away) and has a significantly lower impact than importing slates (e.g. Spain - approx. 1,250 miles away; Canada - over 2,800 miles away).

2. As extensions to the hospital car park were also planned, the concrete tiles from the existing roof were crushed and used as hardcore for these sections. This prevented over 330 tonnes of waste from going to landfill and removed the need (as well as the carbon cost) to bring additional materials to the site for this purpose.


The logistics of the project were complicated by a number of further issues:

i) Access to general areas.

As the South-East section of the hospital grounds provided no vehicular access, a temporary road was provided to the Southernmost ward, using the some existing removed tiles as hardcore. The remainder of the existing tiles were set aside for the planned car park extensions mentioned above.

ii) Access to the workface.

The areas immediately adjacent to the building consist of lawned, landscaped gardens which were to be preserved and protected at all costs. Access for the distribution of materials was therefore only available at the end of each roof section. As the lengths of these wings was typically 60 metres long, a significant amount of manpower was required in order to organise and achieve the distribution of the materials being removed and the new slates (almost 100,000 of them), felt, batten, etc. for installation.

iii) Inclement weather.

The work was scheduled to be carried out through the Winter months. The wind and rain which was suffered brought about obvious complications in terms of maintaining the integrity of the building envelope. They also created a vicious circle as, whilst this weather hampered our progress, it also generated pressure from the client, anxious to achieve the respective phase completion as quickly as possible.