Headfort Court – Conservation method statement for repairs to masonry steps

Conservation method statement

for repairs to masonry steps

Headfort Court, Headfort House Kells, County Meath.

Date: August 2013

1 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

GENERAL MATTERS. Scope of proposed repairs: Conservative repairs are proposed to the existing masonry steps and landing at the front entrance. The steps are formed in limestone blocks with limestone flags to the landing all supported on a rubble masonry arch with wrought iron railings to the sides. The steps have become displaced over time due to settlement and weathering out of the original lime/sand mortar bedding with vegetation growth and loose masonry to the side walls which is threatening the stability of the arch. The iron bars supporting the handrail are also distorted arising from movement in the steps and there is localised corrosion at the foot of the bars. Some of the stone blocks are broken and in general the steps are very uneven and dangerous. The proposed repairs will involve lifting the masonry flags and steps to allow effective repairs to the unsound masonry to the side/supporting walls and resetting the steps in their original position with lime mortar bedding and pointing. The wrought iron railings will also need to be carefully removed to allow the steps to be re-built and damaged bars straightened/repaired, thoroughly painted and re-assembled. Record photographs and drawings are included in the appendix.

Workmanship: Only operatives who can demonstrate training, experience and competence in the use of the products and methods outlined in this specification are to be employed in the works.

Sample Panels: The contractor must complete samples as outlined in this specification and seek approval from the surveyor before proceeding with the relevant item of work. The samples will be used to confirm the most appropriate mortar mixes, repair techniques etc and will be used to check the competency of the operatives in the techniques required in the repair process. Trial samples approved by the surveyor will be retained and used as a reference for the standard of work to be achieved during the works.

2 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Access & lifting equipment: The contractor will be responsible for arranging suitable temporary protection, access equipment, working platforms and lifting equipment sufficient for all the works proposed.

Protection & cleaning: Provide suitable temporary protection to all fresh mortar during the works to prevent damage as specified further below. Provide suitable protective dust sheets and coverings to prevent soiling and staining to adjacent parts of the property and the adjoining buildings. All damage and disturbance to these elements shall be made good to the satisfaction of the surveyor at the contractor’s expense. Allow for cleaning up all areas affected by the works on a regular basis and leave the site clean and tidy and in good order at completion.

Health & Safety: Comply with all relevant aspects of the current health, safety and welfare at work acts and regulations. Ensure all necessary tools and personal protective equipment is in place before commencing any of the works.

Insurance requirements: Contractors must carry all necessary Employers Liability, Public Liability and Contractors All Risks insurances.

SPECIFICATION FOR MATERIALS & WORKMANSHIP Mortars Natural hydraulic lime/sand mortars The following are the main materials that will be used: Natural hydraulic lime: Natural hydraulic lime to BS EN 459 – 1. Manufacturer/supplier: St. Astier, Roundtower, or other equal and approved manufacturers: (Supplier Contacts: Conservation Technology, Davitt Road, Dublin Tel: 01 4559511 or Traditional Lime Company, Carlow, Tel: 059 9151750). 3 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Types: NHL 3.5 for general building and pointing. Delivery: Lime to be delivered to site in bags clearly labelled. Storage: Lime must be kept stored for a maximum of 8 months internally in dry conditions and rotated as required according to use and delivery. Opened bags must be sealed and kept dry. Sand for lime/sand mortars Quality, sampling and testing: To BS EN 13139. Types: Coarse sand: washed river or pit sand, ideally of local origin, provide samples for approval before bulk ordering. Grading: Where specified coarse sand shall be sharp gritty sand with the following grading unless otherwise specified.

% particles retained

Sieve Size

2

6.00mm

3

3.35mm

6

2.36mm

15

1.18mm

23

0.60mm

32

0.30mm

15

0.15mm

4

0.075mm

Fine sand: Where specified fine sand shall be well graded fine washed pit or river sand, ideally of local origin, grading as outlined below. Provide samples for approval before bulk ordering.

% particles retained

Sieve Size 4

Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

0

6.00mm

0

3.35mm

0

2.36mm

6

1.18mm

12

0.60mm

34

0.30mm

30

0.15mm

18

0.075mm

Grit: Where specified grit will be required to blend with other aggregates to produce a well graded aggregate suitable for larger beds and joints. Grit shall be well graded fine washed pit or river sand, ideally of local origin, grading from 3.35 up to 12mm. Provide samples for approval before bulk ordering. Sieve Analysis: A sieve analysis report confirming the above grading must be provided on each delivery of sand if requested by the surveyor. Blended aggregates: Where suitable well graded aggregates are not available a blend of coarse sand and grit may be used. Storage: Sand to be kept covered at all times to reduce moisture content and bulking which could distort the mix proportions. Sand void percentage: Specified binder : sand proportions may be varied by the surveyor following completion of testing to determine the sand void percentage. Samples of suitable aggregate shall be provided to facilitate completion of the void ratio test. Delay bulk ordering of sand until void test ratio is completed and samples approved by the surveyor.

Mortar Production The contractor should note that working practices for the production and aftercare of lime/sand mortars are different to cement/sand mortars. Contractors will be required to demonstrate competence in the use of natural hydraulic lime mortars.

5 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Definitions Batching: The process of adding the constituent materials to the mixer in the prescribed quantities. Gauge: Container of specified volume by which the quantity of a mortar constituent can be measured during batching.

Mortar Production Site prepared natural hydraulic lime : sand mortars: Batching: Batching of lime and sand by volume. Use clean and accurate gauge boxes or buckets. Sand must be dry or make appropriate allowances for bulking of wet sand. When buckets/gauge boxes are full tap the sides to settle the contents and fill to level. Water: Water for mixing mortar shall be from a clean potable water supply. Mixing lime : sand mortar: Follow the lime manufacturer’s recommendations for each stage of the mix. Thoroughly mix lime with sand in a roller pan or paddle type mixer in the dry state. The use of standard drum mixers are permitted but extra care is required to ensure the constituents are thoroughly mixed. Add small amounts of water and mix again for at least 20 minutes or until thoroughly mixed. Allow to stand without drying out for at least one hour before using and mix again without adding additional water to achieve the required workability. Working time: Mortar may be re-worked within an 8 hour period. Knocking up day old hydraulic lime mortars is not permitted. Contamination: Prevent intermixing with other materials, including air entraining agents, plasticizers, and cement.

General Fixings & fastenings 6 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Materials: For masonry fixings use only stainless steel or similar non-ferrous dowels, masonry nails and or screws and plugs. Type: Proprietary types to suit substrate, loads to be supported and conditions expected in use. Submit samples on request Integrity of supported components: Select types, sizes, quantities and spacings of fixings, fasteners and packings to retain supported components without distortion or loss of support. General usage: To recommendations of fastener manufacturers and/ or manufacturers of components, products or materials fixed and fixed to. Penetration of fasteners and plugs into substrate: To achieve a secure fixing and to suit existing fixing holes, otherwise generally no less than 30mm into sound material. Lead Rolled lead sheet: To BS EN 12588. Paint & primers Manufacturer & Suppliers: Allback/Linseed Oil & Wax Company Primer: Allback Red Oxide Linseed Oil Primer Paint: Allback Linseed Oil paint

General Masonry Work Bedding and pointing masonry Mortar mixes: Mortar mixes for re-building, re-bedding and re-pointing are as follows: · Bedding to steps: 1 part NHL3.5 a n d 2.5 parts sharp gritty sand or if blended aggregates used 1 part NHL3.5, 1 part grit and 1.5 parts sharp/coarse sand. · Bedding to flags: 1 part NHL3.5 and 2.5 parts sharp gritty sand or if blended aggregates used 1 part NHL3.5, 1 part grit and 1.5 parts sharp/coarse sand. · Bedding to rubble masonry : 1 part NHL3.5 and 2.5 parts sharp gritty sand or if blended aggregates used 1 part NHL3.5, 1 part grit and 1.5 parts sharp/coarse sand.

7 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

· Pointing to limestone steps & flags: 1 part NHL3.5 and 2.5 parts sharp gritty sand or if blended aggregates used 1 part NHL3.5, 1 part grit and 1.5 parts sharp/coarse sand. · Grouting to voids by gravity feed: 1 bag NHL3.5 and 40 litres(55kg) fine sand with enough water to make a fluid paste.

Mortar samples: Allow for making 2No. 100 x 100 x 25mm square samples of the above mortars using two different sand samples for final approval prior to bulk ordering of materials and commencing the works. Laying stones: Accuracy: §

Courses: Level and true to line.

§

Faces, Angles & Features: Plumb and consistent with existing work.

§ Setting Out: Refer to drawings/photographs as necessary. Achieve satisfactory junctions and joints with adjoining or built-in elements or components. Mortar joints: § Sizes: All joint sizes to match existing work and as indicated on drawings. §

Laying: full bed of mortar with all joints and voids filled.

§

Appearance: Neat and consistent.

§ Finish: After the initial set stipple with a stiff brush to remove laitence and give a good coarse texture. Cleanliness: Keep facework clean. Wash with stiff bristle brush and clean water. Mechanical abrasive or chemical cleaning methods to remove marks and stains are not permitted. Control Suction: Dampen all stones as required to reduce suction. Do not soak. Rough masonry resulting in large joints: use stone pinnings where necessary throughout to reduce thickness of mortar beds and joints. Fine masonry joints: Set stones in thin mortar bed to match original joint thickness. Use existing or new slate spacers to suit original joint width and retain uniform joints throughout.

8 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Protection of new work Adverse weather General: Do not use frozen materials or apply mortar to frozen surfaces. Air temperature: Do not use specified mortars: at temperatures below 5oC and falling or unless temperature is at least 5oC and rising. Temperature of walling during curing: Maintain temperature above freezing with suitable coverings/insulation until mortar hardened. Protection: Provide adequate protective coverings to fresh mortar incorporated in the works against the effects of heavy rain, strong sunshine, drying winds and frost. Method: § Masonry : Reinforced plastics sheeting adequately secured at the top, base and sides against movement. In hot weather use damp hessian sacking material over new work to prevent rapid drying out. § Timing: Allow sufficient time for curing and putting protective coverings in place before the end of each day’s work.

REPAIRS TO MASONRY & WROUGHT IRON METHODOLOGY Removal of vegetation Carefully remove clematis from side of balustrade and small amounts of fern and other small vegetation from the masonry side walls by hand and clear away and notify the surveyor to allow assessment and recording of the condition of the masonry before proceeding further.

Equipment Before commencing any masonry repairs suitable equipment must be p r o v i d e d f o r dismantling and lifting masonry units including iron 9 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

balustrades. Suitable equipment would include a mobile tele-handler or manual hoist with belt/chain slings and shackles. The contractor will be responsible for devising a suitable methodology to prevent personal injury and damage to the masonry/balustrades. The contractor should note that there are cellars located below the driveway and these may not be suitable for heavy loading and suitable control measures will be required to avoid damage. Exact methodology to be provided to the surveyor for review before commencing the works.

Preparatory work ·

Install suitable temporary hoarding to the works area for safety purposes and to avoid unauthorised entry to the works area.

·

Provide temporary coverings to existing tarmac surfaces, walls and paved areas adjacent to the works areas as required.

·

Before dismantling any masonry check all levels and measurements on drawings supplied to facilitate reinstatement and notify the surveyor of any discrepancies found.

Dismantling iron balustrade Existing balustrade to be removed by the blacksmith before any masonry is removed. ·

Where possible balustrade to be removed in a single unit without dismantling joints between handrail and vertical rails.

·

Make up and install suitable timber support rails to sides of balustrade using 50 x 38mm battens notched for square bars and secure in place before dismantling to assist in handling and minimise distortion during removal of the balustrade.

·

Carefully remove all lead filler to mortices in stone steps to free base of vertical rails and to end of handrail by drilling out the lead with closely spaced holes, maximum 8mm diameter. Use sharp steel bit with variable speed drill and use slow drilling speed to minimise jamming. Drill out lead all round before carefully prising out all lead to free bar ends.

·

Carefully lift out balustrade and set aside for further repair as detailed below.

Dismantling masonry steps 10 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

·

Carefully remove mortar from joints and loosen bedding mortar to free stones before lifting. Do not force joints apart without loosening mortar beds. Any solid areas of mortar including cement mortar should be removed in sections; make starter holes with a suitably sized masonry bit and rake out mortar where necessary.

·

Use suitable crow-bars with timber shields and wedges to move stones away from beds. Secure the stone with a lifting sling and carefully raise the stone vertically to avoid damage to the stone or adjacent stones.

·

Retain any original spacers used in the joints for inspection by the surveyor and for possible re-use.

·

Label stone on a concealed bed face using suitable markers to identify their original location and orientation using the numbering system set out on the drawings.

·

Set aside all masonry and other items for re-use on a suitable solid base. Stones should be stored on suitable plywood sheets or wooden pallets. Where possible do not stack stones to avoid damage and use timber spacers between adjacent stones.

·

When stone steps and flags have been removed retain original bedding mortar etc. for examination by the surveyor and seek approval before removing. Set aside small stones, pinnings etc for reuse.

·

Repair broken stones by stitching together using at least 2No. 10mm diameter stainless steel dowels set minimum 50-75mm into each side of the stone. Secure dowels with proprietary epoxy resin based stone adhesive. Mask off front faces of stone as required to avoid staining and clean/prepare broken faces and bond together using specified stone adhesive. Allow adequate time to set before building in.

Consolidating masonry arch & side walls ·

Clear away soil and unsound bedding mortar to expose upper faces of stone walls/arch below the steps and landing, notify the surveyor and await further instructions.

·

When directed remove unsound masonry and record position of stones on bed faces and set aside for reuse. Only remove loose or displaced areas of masonry as directed by the surveyor.

·

Prepare sound areas of masonry for re-bedding previously removed stones by brushing down to remove dirt and loose mortar. Observe all specified requirements for preparation and use of lime mortar and general masonry practices. 11 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

·

Where directed re-bed stones in their original position using lime/sand mortar as specified. Keep mortar beds to a maximum of 20mm to avoid excessive shrinkage in the mortar.

·

Where directed flush out voids in stones using low pressure water spray and grout with specified lime/fine sand grout.

·

Allow for making up levels to masonry side walls and arch structure as necessary to compensate for historic settlement and to provide solid beds for steps and flags to landing by bedding additional stone and or slates in lime/sand mortar beds. Keep mortar beds to a maximum of 20mm to avoid excessive shrinkage in the mortar.

·

Observe specified requirements for protection and aftercare of lime mortar. Dampen down using fine mist spray at intervals as necessary to avoid rapid drying.

Re-bedding steps and flags ·

Complete sample of re-bedding and joint finish for two of the steps for approval by the surveyor before proceeding further.

·

Re-bed stones in their original position and to correct level and line as per the record drawings. Use hydraulic lime mortar as specified incorporating slate and or lead spacers and packers and lay all stones on full width mortar beds. Observe all specified requirements for preparation and use of lime mortar and general masonry practices. To minimise shrinkage avoid mortar bed joints exceeding 20mm in thickness. Where bed joints will exceed this dimension lay under courses with suitably sized stones and allow for curing before placing steps/flags.

·

Observe specified requirements for protection and aftercare of lime mortar. Dampen down using fine mist spray at intervals as necessary to avoid rapid drying.

·

Leave joints in the stones clear as the works proceeds to allow beds to cure fully before pointing the joints and cover to keep joints clean. Allow at least 3-4 days for curing before pointing the joints.

Re-pointing rubble masonry side walls Only weathered out/defective mortar joints to be re-pointed as directed by the surveyor after vegetation clearance.

12 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

·

Provide samples of raking out and pointing tools to be used and complete sample of raking out and re-pointing to a section at least 500mm square for approval by the surveyor before proceeding.

·

Carefully remove any defective mortar from joints using suitable sized spike/chisel and hammer. Angle grinders are not permitted. Any cement mortar should be removed in sections, make starter holes with a suitably sized masonry bit before raking out. Retain any original stone pinnings for reuse.

·

Clean out joints as required to remove any dust and dirt and dampen as necessary to control suction. Observe all specified requirements for preparation and use of lime mortar and general masonry practices. Apply the specified hydraulic lime mortar in a stiff mix using a suitable pointing iron and press mortar firmly back. Fill joints in stages and repeat the process until the entire joint is filled. Insert slate/stone pinnings to wide joints where required to minimise shrinkage.

·

Finish mortar joints to the face of the stones, press back firmly and strike off flush. All finished joint faces should be slightly recessed from weathered edges of the stones. When mortar is semi-hard tamp with a stiff bristle brush to give open texture and remove laitence.

·

Observe specified requirements for protection and aftercare of the mortar. Dampen down using fine mist spray at intervals as necessary to avoid rapid drying and cover as required.

Re-pointing joints in steps & flags ·

Provide samples of pointing tools to be used and complete sample of re-pointing to at least one horizontal and one vertical joint for approval by the surveyor before proceeding.

·

Mask off edges of stones using suitable strong canvas backed adhesive tape to minimise staining.

·

Observe all specified requirements for preparation and use of lime mortar and general masonry practices. Clean out joints as required to remove any dust and dirt and dampen as necessary to control suction. Apply the specified hydraulic lime mortar in a stiff mix using a suitable pointing iron, same width as joints (joints will vary from around 10 to 25mm in thickness) and press mortar firmly back. Fill joints in stages and repeat the process until the entire joint is filled. Insert slate/stone pinnings to wide joints where required to minimise shrinkage. 13 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

·

Finish mortar joints to the face of the stones, press back firmly and strike off flush. All finished joint faces should be slightly recessed from weathered arrises of the stones. When mortar is semi-hard tamp with a stiff bristle brush to give open texture and remove laitence.

·

Observe specified requirements for protection and aftercare of the mortar. Dampen down using fine mist spray at intervals as necessary to avoid rapid drying and cover as required.

·

Remove masking tape and clean down all masonry on completion.

Repairs to iron balustrade The following works are to be completed in the forge by an experienced and competent blacksmith. Any new iron for repair/replacement elements to be real wrought iron from an approved supplier or wrought iron from salvaged supply. Mild steel or other substitute materials are not permitted. Material samples/relevant documentation to be furnished for approval of the surveyor. All repairs and new elements to be hand wrought using traditional forging methods.

Repairs to iron balustrade Existing balustrade to be repaired and replaced without dismantling joints where possible. ·

Remove all existing paint layers from the iron using approved methods such as flame cleaning or soda blasting taking care to avoid any damage to the original mill scale surfaces. Suitable lead abatement measures must be employed to control harmful lead and all lead paint residues to be safely disposed of. Store the balustrade in a suitable dry environment before and during painting.

·

Bar ends embedded in masonry to be entirely de-rusted and checked and approval sought on repairs to wasted bar ends before proceeding.

·

Only bar ends reduced beyond 60% of the original bar section to be repaired by cutting and forge welding new matching sections o f wrought iron.

·

Distorted ends of bars to be repaired by heating and straightening as required.

·

Redecorate the balustrade fully before reinstating.

14 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]

Headfort Court – Conservation method statement for repairs to masonry steps

Re-decoration of iron balustrade The methodology o u t l i n e d b e l o w a n d t h e paint manufacturer’s recommendations should be strictly followed. ·

Cleaned iron should be stored in dry conditions and painted as soon as possible.

·

All exposed iron should be cleaned and freed of dust, dirt and grease. Use linseed oil soap as necessary to clean surfaces before painting.

·

Any gaps in bar joints should be thoroughly sealed with an approved flexible and coat-able silicon mastic.

·

Apply one coat of red oxide primer to all iron surfaces.

·

When dry apply three coats of selected colour linseed oil paint.

·

All iron surfaces should be fully painted before replacement and apply one final coat after installation.

Leading-in ·

Clean out existing holes in stone steps and ensure stone surfaces are bone dry by applying gentle heat as necessary to minimise lead spitting. Insert lead shims in base of holes as required to level up and support the balustrade.

·

Install balustrade in position and to proper level and line and secure with temporary props as required.

·

Lead-in all bar ends by carefully filling holes with molten lead applied using a suitable ladel.

·

Once the lead has solidified tamp down using a leading-iron and hammer. Finish flush with stone surface and cut off excess lead flush with a chisel.

·

Horizontal hole for handrail bar may be filled with molten lead applied from a clay cup or by hammering in solid lead in stages all around.

·

Retain props to balustrade in place until lead has solidified and remove on completion.

15 Liam Mulligan Chartered Building Surveyors & Historic Building Consultants, 1 Carrick Street, Kells, Co. Meath Tel/Fax: 046 9249728, Mobile: 087 2791705, Email: [email protected]