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This article I wrote on repairing damaged stone sills first appeared on the traditional painter website and is part 3 of a series including: repairing marble and reparing upvc windows, doors and sills.
This is Spondon Methodist Church which is situated along the main A52 dual carriageway towards Derby City Centre. Its a very well used social meeting point with local parishioners and residents alike. This 1930s building replicates the typical local parish church and village hall found in most towns and villages throughout the UK. Unfortunately the building was looking rather tired especially the architectural stonework, which seemed to be crumbling away…
In the early part of 2008 I was contacted by Mr Mike Morton the property steward for the church and in charge of the buildings maintenance. Mr Morton works for National house builder Miller Homes, who have a regional office based just down the road on Pride Park. I had previously carried out work for Miller Homes repairing some damaged sandstone features on one of their local developments and the buying department had referred me to Mr Morton.
SURVEYING THE EXTENT OF DETERIORATION:
I was informed that this particular issue had been on their maintenance agenda for several years, but despite contacting various local contractors, including builders, stonemasons and various other trades to quote for the work, none of them were forth coming. The church was due to celebrate its 75th Anniversary in June 2009 and the committee and parishioners were all now very keen to spruce up the building. During my first site visit and inspection my initial thoughts were that the stonework had been helped in deterioration by large volumes of traffic using the A52, which had resulted in heavy CO2 emissions. This would have to be one area to consider when sourcing suitable repair and finishing products.
There are over 100 individual stone sills, heads and various arches and features around the building which all showed various stages of erosion. Consideration was also noted to the original leaded glass windows on the main building, which could become easily damaged during the works. My initial survey and inspections had shown that most of the low level sills had deteriorated quite badly as well as some heads and features. This had been caused by the ingress of water attacking the steel reinforcing bars causing oxidisation, which in tern had forced the concrete to blow off.
Having sourced suitable products and after carrying out further site tests, I was able to put together a repair system and compile a method of works together with a quotation and programme of works. Technical Data Sheets were obtained from the product suppliers and Risk Assessments and COSHH Assessments carried out and submitted to the property steward. All documentation was accepted and several weeks later the stone restoration work began.
Stage 1- Repairs
Stage one of the works involved cutting back the eroded stonework to a sound substrate, revealing the oxidised reinforcement bars. These were prepared by hand or with mechanical aid wire brushes to bright steel and then after all dust had been removed, primed with the recommended steel primer. To maintain the original shape of the stonework, I prepared several wooden shuttering forms on-site. These were shaped to match the concave face to the front of the stonework; this would help me to re-produce the original shape in the finishing stages.
A repair compound was poured into the shuttering and left to cure overnight. The shuttering was struck and followed by coating the repaired area with Acrylic Latex bonding coat in preparation for the next stage of a Lightweight Mortar.
I soon discovered that the initial repair compound was drying out to quickly through evaporation and so to overcome this I lined my wooden shuttering moulds with duct tape to act as a vapour barrier and covered over the repairs with plastic sheeting, once cast. This helped to retain the moisture levels and together with short stainless steel fixing rods. This process now gave my foundation repairs a rock solid bond to the original substrate.
Stage 2 – Repairs
The Lightweight Mortar is a fiber reinforced powder mix which is applied with small plasterer’s type finishing trowel and small wooden float. Throughout this application the mortar was sprayed with a curing retarder which helps maintain correct hydration of the mortar and prevents cracking. The repairs were again covered overnight with plastic polythene sheeting to help curing with the correct hydration.
With some careful troweling and shaping I was able to reproduce the shape of the stonework almost exact and after each one I did, my technique seem to improve.
Although this was a stone restoration project, I maintained the same principles as I would with any painting or decorating job; good preparation, masking out where necessary, understanding of the products and any limitations as well as planning and carrying out my well thought out schedule of works in advance.
Stage 3 – Finishing
Once all repairs were completely cured the stones were coated individually with an application of special leveling coat – a two component Portland cement based powder mix. Whilst the leveling coat was still in a wet state an application of finely crushed stone aggregate was applied through a grit blasting gun with compressed air, this would produce a textured finish very similar to the original stonework.
I masked off areas adjacent to the brickwork using 3M masking tape from a automotive factors. The 3M tape has a great sticky backing and is ideal for masking around stone and brickwork.
Stage 4 – Final Stage
Before the finishing coats could be applied it was necessary to cover the newly textured stonework with a bridging coat of Keim Granital Grob this product is designed for previously painted and repaired surfaces.
Finally 2 x coats of Keim Granital Paint were applied in the chosen colour. The first coat was diluted by 20 – 30% by weight with Keim Granital Dilution and the second coat was applied undiluted. The results ended with a very pleasing aesthetic finish that looked virtually the same colour and finish to the original stonework. Throughout this project I used and sourced a variety of products which took quite some resourcing and at times not without problems.
The end result was a satisfied client, some new skills for me and what is now a tried and tested process I can offer to other potential clients. Four years on, the stones still look as good as the did then!
THIS IS WHAT SPONDON METHODIST CHURCH HAD TO SAY:
This is a reference for Russ Pike, who under took a major external masonry repair project at the above premises. Russ provided a first class service from initial enquiry to completing the work.
The project itself was not straight forward. The building was erected in the 1930′s using precast concrete sill and lintels to the window and door openings. Over the years parts of the original reinforcement had spoiled with chunks of concrete breaking off, exposing the steel below.
Russ provided the church with an all risk quotation after spending a long time in resourcing the necessary products and estimating the extent of the work. The work was commissioned and Russ attended the site at the agreed time. He spent a long time in agreeing the type of finish and colour of the final repair with the members of the church, until they were satisfied that the right choice had been made .
During the repairs it became apparent that the material that was applied to provide the final finish coat was staining. At much expense to Russ pursued the supplier of the material to rectify the problem. After much chasing and research Russ completed the job using a different material. Work that had been completed had to be gone over again to get the consistency of colour and texture. The work was completed and a highly professional finish was achieved, which has since been greatly admired and as a consequence has greatly enhanced the external appearance of the building.
It is without hesitation that Spondon Methodist Church recommends Russ Pike to anyone to carry out similar work.
Mike Morton – Property Steward, Spondon Methodist Church.
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First and foremost I am a Traditional Painter with traditional skills and working ethics.