MAGENTA BUILDING CONSERVATION LTD
Stonemasonry, restoration and complete repair works to historical and ecclesiastical buildings.
Technical Information
Rope Access
Method Statement example:
ST. MARY'S CHURCH, BRADING. OCTOBER 2005 THE GAINING OF ACCESS TO THE SPIRE USING ROPES.
Magenta Building Conservation Limited uses IRATA methods of safe work practices during all rope access work.
Magenta only uses qualified technicians for climbing work.
Magenta technicians will use all appropriate certified and logged personal and other equipment.
Magenta technicians will carry out all on-site checks of equipment as usual practice for IRATA members.
All static rigging slings and cables and static belay fixings are checked prior to and during use.
All equipment, personal and otherwise, is to be checked so as to be suitable for the purpose and of adequate strength.
One climbing technician will always be prepared and available to attend to any unexpected circumstance required by the lead technician i.e. versed in rescue techniques, descending and ascending.
The Tower and Spire.
The overall height is approximately twenty metres. The underside of the spire has an independent scaffold from the ground to within seven metres, approximately, of the top of the spire. The technicians will be working on the area above the scaffold from the parapet to the top of the spire (seven metres).
Certified, new (or in as new condition) rope access equipment will be employed including harnesses, chest ascenders, maillon screw links, sit tos, descender stops, foot jammer cowstails, shunt back - ups, independent cowstails, ropes, anchors, slings, and carabiners.
The harnesses will be attached from the chest to maillon screw link to chest ascender, sit harness to descender stop, foot jammer cowstail. Shunt back up, cowstail. Two independent cowstails. Connected to two independent dynamic ropes, one of which will be a 'working rope1 (load), the other will be a safety rope. (Two ropes will always be employed thereby providing a safety back-up) The ropes to be 10/1 lmmEN1891, rigged to separate anchors with slings, carabiners and figure of eight knots. The fixed point anchors rigged to will be generally parts of the building structure. Permanent anchors, such as stainless steel multi-directional hangers (EN 795 Ai) can be installed if deemed necessary.
Access will be gained to the initial anchorage point by belay using grillons.
Access will be gained for the installation of the main and safety anchor points by using belay points progressively up the spire, these can be secured using varying length grillons and static cables horizontally. The rope access technicians can clip into these points using a short lanyard / cowstail and position the next grillon horizontally above them, then move on to the next belay point, clip in and position the next grillon horizontally, clip in and repeat the process making sure they are always secured in two points and using a back - up device.
The spire is unusual as it sits on the inside of the tower walls, therefore, there is a wide parapet all around the base of the spire, including the base of the broaches. The spire is also quite low pitched, being fairly wide compared with its height; with appropriate slings etc. it will be easy to fix the initial belay point from a ladder as long as the operative is clipped into a fixed point independent of the ladder.
Any harnesses etc. can be secured using static fixings/locking carabiners/low stretch rope EN1891 from anchor or belay point/slings EN566
We will not be using any chemical or expansive anchor points as the spire is of weakly bonded limestone with high silica content; in practical terms it is like a soft sandstone.
Once in working position, all the usual and relevant health and safety legislation and good working practices will be followed i.e. P.P.E. electrical safety equipment regulations etc
Working Over Water
Method Statement example:
COLDHARBOUR MILL
When working above or in water the following precautions are to be taken:
A fence or barrier is to be provided to any structure or scaffold where there is a risk of persons falling from such structures into water.
Warning signs and notices are to be displayed.
A buoyancy aid of a tested and approved pattern is to be worn by all personnel working over water.
Suitable rescue equipment, e.g. boathook, lifebelt or lifeline, is to be in position before work commences.
The use of any electrical equipment is to be strictly controlled and steps take to ensure that leads are not long enough to touch the water.
All electrical equipment should be connected to lines to prevent their accidental dropping into water causing possible electric shocks.
All personnel are to be instructed as to means of raising alarm and rescue drills.
Any works over water are to be carried out by a minimum of two persons. No lone working will be permitted.
Special care must be taken in fog, snow or rain when extra checks are to be made by the site supervisor.
The water level should be monitored on a regular basis and account taken of the possibility of rising water levels following heavy rainfall.
The site supervisor or a nominated person is to make frequent and regular checks on numbers of personnel working.
Lifting Heavy or Large Fixtures
Method Statement example:
ST. JOHN THE BAPTIST, WELLINGTON.
Lifting floor beams into tower. Hazards:
Unintentional release of load
We intend to drill through the timber beams and thread the rope through this hole and fix with a figure of eight knot to provide a positive fixing to the load.
Unplanned movement of load
We intend to belay the beams during the lifting process to eliminate anything other than vertical movement.
Damage to equipment
Softwood timbers are to be fixed across the face of the organ to eliminate any chance of the beam brushing against the organ pipes during lifting. The timbers will be held in place with folding wedges between the stonework arch.
Crush injuries to personnel
Belaying the load whilst lifting will eliminate the need for any operative to be beneath the beam during lifting. The load will be lifted from above with personnel wearing fall arrest equipment whilst working near the open hatch.
Method Statement:
The methods used for low-pressure void-filling grouting are as follows:
The area to be grouted is to be carefully cleaned and inspected and a decision needs to be taken as to which method and type of grout is to be employed. The most common grouts now used for historic buildings are Pozzament Heritage grout, Pozzament St. Paul's mix, (one of which is cement based and one of which is hydraulic lime based) hybrid on site mixed grouts such as NHL 3.5 hydraulic lime, P.F.A. (pulverized fuel ash), Bentonite / Wyoming clay mixed at proportions of five parts P.F.A/one part NHL 3.5/ four parts water, approximately 5 - 10% Bentonite.
Alternatively, NHL 3.5 P.F.A. and oolitic stone dust depending on the application and flow rate required, the materials such as stone dust can be sieved to the required level either mechanically or by suspension in water.
Pure lime putty can be used as a base for grout but generally is avoided due to the fact that an area of walling suited to grouting is usually within the centre of a mass of masonry and therefore the 'set' for the grout could be very slow or practically unattainable. Also, some materials need constant activating during mixing and pouring this can result in separation of materials which is to be avoided.
Where the mass of masonry has to withstand applied hydraulic/water pressure, such as a harbour or a dam wall, either a quicker setting cement or marine grade grout is required.
Methods of administering grout differ from situation to situation, but generally a decision is made based on the condition of the wall; if the wall is narrow in breadth and is constructed with little through-bonding or is constructed of very small nodes or unit sizes, such as flintwork, or low quality small rubblework, then the amount of grout-fill and pressure of application is kept low as too much wet-fill administered with an excess head of pressure can easily push the masonry apart. In cases where the walling is very unstable it is sometimes necessary to introduce mechanical ties to bond the wall together first, then, once stabilized, to remove odd, individual, non-through stones and carefully grout the affected area from ground up using, even, as little pressure as from pouring the grout through a watering can, re-fixing the individual stone as necessary whilst carefully monitoring the conditions of the walling and amount of wet liquid poured. If employing the above tentative approach, bear in mind the limitations of achieving a reasonable flow of grout, as with only, say, 300mm to 600mm head of gravity pressure through a 22mm diameter pipe, the amount and spread of grout will be very limited.
Generally the term 'low pressure' means, when used on mass masonry, approximately between three metres and six hundred millimetres in height, through a twenty two to twenty five millimetres in diameter pipe. For example, for a solid masonry wall which is built of two leaves of walling with bonding through-stones etc. and a lesser quality fill which shows signs of either long vertical cracks (A) or washed out, loose hearting fill (B) we would fully rake out any defective pointing as necessary, clean down and inspect and if practical, drill through the joints into the core of the wall with a twenty five millimetre masonry drill to attempt to connect with the voids within the walling (A) at four hundred to five hundred millimetres along the crack (B) five number holes per square metre.
Knowing where to drill the holes is a case of educated guesswork: if you are experienced in the practical construction of stonework and rubblework, you should have a fair idea by looking at the existing stone face sizes and proportions relative to each other stone which is likely to be a through stone.
Once all the holes are drilled they can be tested to see which ones will take grout by washing out with a hosepipe of water. This is not always applicable because the introduction of more water into a mass of walling is sometimes not advisable, although more often successful grouting will not be achieved without washing out and dampening of the voids prior to grouting, even if ideally you would not allow more moisture to be introduced to the mass of walling.
At this stage, mark up drill holes which take water i.e. connected to the void, then re-point the wall as necessary and fill unusable holes. In some cases, re-pointing can be carried out after the grouting operation, especially when the core is remote from the face of the walling. Allow the pointing to cure/set ideally beyond the initial set. Set up the grout equipment, grout and mixing equipment as close to each other as possible. It is important to check thoroughly for small holes, cracks or voids in the areas to be grouted as, if successful, grout will find any small tracts within the wall. Check that you are not likely to fill service ducts, cable conduits, etc. or push grout out around window openings or window frame fixings etc. Also check around and plug if necessary where timbers, beams, templates or corbels connect into a wall. For instance, where floor joists are built into a wall then one would grout up to the underside level of the joist then if possible, grout a thicker in consistency single layer just above the joists monitoring how much is being taken (i.e. not filling a ceiling void!). Then leave to set before carrying on the next level with the normal mix.
Mixing should ideally be done using a mechanical, slow turning plasterers' whisk. The consistency required will vary; in simple terms, thicker than good quality emulsion paint and thinner than porridge. Wetting the holes immediately before grouting is most effective (from grouting terms!) Continual mixing whilst pouring is usually required.
Continually check where the grout is going. (We have had grout exiting a hole in a dam wall fifteen metres away from and two metres higher than the hole we were grouting!) Once the head is established, keep the length of pipe to a minimum as resistance along the length of pipe will have a bearing on the flow rate. When grouting cracks (A) depending on the amount of grout being taken only attempt to fill in say, two to three holes at a time, fill them and leave the grout to settle and start to set. As the nozzle is removed from each hole it can be temporarily filled with clay. When grouting walling i.e. (B) then it is preferable to work horizontally along the structure and allowing set to occur before re-visiting the same area of elevation, remembering that with three metres of head, say, without knowing you could be filling an area up to three metres above the nozzle.
All equipment must be kept clean and free of setting grout as with the surrounding areas i.e. scaffolding etc. and spilt grout should be thoroughly washed off walling, masonry and structures before it sets and stains; clean water and churn brushes are usually sufficient.
Good practices of manual handling should be applied throughout the operation as often the bags of grout will exceed twenty kilograms. More often grouting works will need to be undertaken from suitable access scaffolding, therefore, all current legislation and good working practices whilst working from height should be adhered to. If the scaffold needs adjusting to facilitate the grout operation, this must be carried out by a competent, certified operative. All the appropriate warning and information signage should be evident adjacent to the works and site curtailedge. Bearing in mind that grouting can be a dusty and messy operation, site operatives and the general public should be adequately protected. All operatives should wear suitable protective clothing and equipment (P.P.E.) i.e. goggles or safety glasses to protect from dust and splashes, disposable or washable overalls, rubber gloves, hard hats and steel-toed safety boots. When drilling or if the mixing whisk is excessively noisy then ear defenders should be employed although when grouting verbal communication is essential between drum/mixer operator and nozzle operator. Dust masks need to be worn, especially during mixing.
At the end of each grout operation or day, all P.P.E. and other equipment should be thoroughly cleaned and stored safely and any residue of grout or unclean water should be disposed of carefully; grout or unclean water should not at any stage be allowed to pollute the surrounding environment including its ingress into any adjacent rainwater or sewage systems. Any residue should be hauled away by a licensed operator.
Grout materials can be caustic and also represent a hazard as dust inhalation. Specific health and safety risk information is provided by suppliers via C.O.S.H.H. sheets. All hazardous materials should be stored securely away from the general public and other operatives.
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Magenta Building Conservation Ltd - Unit D, Milton Mills, Milton Abbas, Blandford, Dorset. DT11 0BQ