Invoking memories of a former golden age
As part of a wider redevelopment of the Kirkgate area in Wakefield, Kirkgate Railway Station has undergone a £4.6m regeneration. The scheme included restoration of this iconic Grade II listed building to its former glory as well as creating space for a café, ticketing, retail, office space and meeting rooms for the community to use and incubation units for small businesses.
Peter Cox Yorkshire was asked to carry out below ground waterproofing at the station but as Branch Manager Gary Laird explains, one job led to another and another! “As is often the case, the client was so impressed with our work in one area, we were invited to tender for others which gave us the opportunity to show off our expertise in dry rot control and specialist timber replacements.”
Our multi-faceted skills on show
There are two basements in the station buildings which at the time were unused. However, future plans included using them for General Office space and so it was important they were dry. At the time of our inspection the area being surveyed had no free-standing water, although the walls were damp with surface moisture.
Damp proofing to basements is covered by British Standards document BS 8102: 1990 and in this instance as the basement is to be used for storage the Peter Cox team recommended a level 3 Performance standard.
Gary said: “It must be assumed that even when current conditions and recent history suggest that hydrostatic pressure is not the source of ingress, it can still occur due to changing water tables, drains becoming blocked and heavy rain causing localised saturation. Therefore we recommended the installation of a Cavity Drained Membrane System to specific areas.”
A drained cavity system is the safest method available for maximum assurance against system failure. This is because ground water is controlled, diverted and harmlessly removed rather than being ‘blocked’ at the point of entry. Consequently the risk of increased hydrostatic pressure is reduced, but directly applied systems generally increase the level of hydrostatic pressure imposed on the structure.
The cavity drain system is designed to control both water vapour and the penetration of ground water. Once the system is in place, three main functions are achieved. Firstly, the system controls vapours, secondly damp pressure is equalised and thirdly, the system will act as a drained cavity system, controlling water ingress.
Gary adds: “Cavity drainage systems work on the principal that any water entering on the ‘wet’ side of the system is either drained away to a sump chamber and pumped to a drainage point – or where local conditions allow – by natural drainage.”
“The effectiveness of the system is dependent upon discharging free water before it can build up behind the system whereby pressure is placed upon the cavity drainage system. It is therefore essential that an effective drainage system is installed and maintained.”
Peter Cox specialists excavated the sub site to accommodate the installation of the sump chambers and then electricians isolated the electrical circuits and removed switches and sockets from the area. We then laid a 100mm floor slab in concrete reinforced with steel mesh and set out a timber form 50mm deep and 85mm wide around the perimeter to prepare for the drainage channel.
It is vital to carry out water flow tests to establish falls and low spots and then we removed any hollows with a latex screed and formed chases before installing a rigid plastic drainage system complete with rodding eyes. We then provided and fit two submersible twin pump assemblies.
Dry Rot Control
“While working in the basement it became apparent that there was extensive decay by the dry rot fungus,” said Gary. “The decay was growing on and within the masonry and we advised the client that if left untreated it could eventually cause major problems. We were therefore instructed to treat the problem.” This meant the team had to remove all evidence of mycelium growth before drilling holes into the masonry at 450mm centres. The hold is then flooded with masonry biocide before applying a surface spray of masonry biocide at a rate of 1 litre per square metre. This was carried out in areas affected by Dry Rot only.
During our Dry Rot survey we found that some of the original oak timber lintels above doorways and windows were also decayed by the fungus. Peter Cox provided a quotation and specification for propping the brick works above the lintels using specialist props and replacing the original lintels with kiln dried sustainable oak over a two month period. We worked in in conjunction with the local Conservation officer and their office when carrying out this part of the work.
Specialist Timber Replacement
Gary said: “The railways station is comprised of several buildings and in building nine there was evidence of decay to the trimmer and joists adjacent to the chimney and in building five we found timber decay in part of the tower roof. Peter Cox experts were again asked to treat the problem.”
In building nine the Peter Cox team cut back the joists to sound timber and removed the timber trimmer before renewing the trimmer fastened with joist hangers. We then bolted and connected new timber joists supported on the trimmer with joist hangers.
The problem was a little more challenging in building five where an inspection of the tie bar in the roof showed the timber decayed at the bearing end with compression of around 75mm. This slumping of the tie bar was dragged down the middle purling causing a crack to open up along the grain.
In order to address this problem we supported the tie beam down to the solid ground floor and cut the tie beam back from the wall 1.40m. We then raised the tie beam slightly to close the purlin crack and drilled four pilot holes into the purlin and injected small quantities of two pack resin.
Full steam ahead
The team supplied and installed a new section of the bar connected to the original with 8mm steel plates before removing the propping and supplying and erecting a lightweight tower. We supplied and fixed six new ceiling joists to replace those removed and then dismantled and removed the tower.
“We were really proud of the various work carried out on Kirkgate Railway Station,” said Gary. “It’s always satisfying to be able to demonstrate the multidisciplinary talents of our experts and it’s very gratifying to have been given the opportunity to work on a landmark building in our region.”