INSTALLATION GUIDE
FLAG INSTALLATION
DESIGN STANDARDS
The back of the flag and top surface of the roadbase should be primed to ensure a good bond. The laying course material should be a modified mortar as specified in BS 7533: Part 4 and spread to give a depth of 30mm after compaction. Cement sand mortars are not suitable for use in this method. The flags should be laid with a 6-10mm joint. A minimum of 12 hours after laying, the flags should be thoroughly wetted and the jointing material, as specified in BS 7533: Part 4 in slurry form, is spread over the entire surface. The material should be moved towards the open joints. Once the joints are full, the flags should be wetted again and a squeegee used to remove excess mortar. The area should not be open to traffic until the bed and joints have reached sufficient strength.
All installations should be detailed and constructed in accordance with the relevant British Standard. This is BS7533: Part 4 for installation. For structural design, please refer to either BS 7533 Part 8 and Part 12 or the Interpave Design Guide. PREPARATION (ALL FLAGS) Sub-grade Clear top-soil: complete sub-grade drainage. Excavate and back-fill soft spots: compact well throughout. Protect sub-grade from adverse weather. Lay geotextile fabric or capping layer (if specified/required). Sub-base Prepare in accordance with the Specification for Highway Works. Lay and compact in layers to a close-textured finish. Open-textured sub-bases may require a binding layer of finer material. General principles Lay paving immediately on prepared bedding, do not leave bedding exposed to weather and/or overnight. To avoid bedding layer damage and creep, lay paving units up slopes and/or away from edge restraints.
Further guidance on the installation and mixing procedure should be sought from the mortar supplier.
2. Flags laid rigidly for category 4 only The laying course should consist of a workable mix of 1:3 cement sand mortar, thickness between 15 and 30mm after compaction. The flags should be laid with a 6-10mm joint. These should be filled within 2-3mm of the surface of the flag with a 1:4 cement sand mortar and pointed as work proceeds. The flags should be compacted down using a paviors maul. 3. Flags laid flexibly for categories 2,3,4 The laying course should be fine aggregate to BS EN 12620 Gf 85 0/04(mp). The thickness of the laying course after compaction should be 30mm. This can be done by either: 1. Screeding the material to give the required depth after compaction. (A small trial area may be required to determine the amount of surcharge). The top 10mm should then be loosened with a rake. 2. 30mm of laying course material should be screeded out and compacted. Then a further 10mm of loose material screeded out on top. The flags should be laid with a 2-5mm joint that is filled with kiln dried silica sand to BS EN 12620 Gf85 0/04 (mp).
Stand on previously laid paving when placing next row.
LAYING
Select site category 1. Heavy duty applications of more than 60 commercial vehicles per day (over 1.5T unladen) 2. Medium duty applications of 60 or less commercial vehicles. 3. Medium-light duty applications – 5 or less commercial vehicles per day. 4. Light duty applications – no commercial vehicles.
Select laying method 1. Flags laid rigidly for all categories 2. Flags laid rigidly for category 4 only 3. Flags laid flexibly for categories 2, 3, 4. LAYING METHOD
Note: the gradings for the laying course material and joint filling material may be found in BS 7533: Part 4.
The flags should be compacted using a vibrating plate compactor fitted with a neoprene sole plate to protect some flags with special finishes in accordance with BS 7533: Part 4. Top up the joints with Kiln Dried Silica sand as necessary and during early life. After laying light coloured paving on site, care should be taken to protect from dirt and detritus while the remaining construction works are completed.
1. Flags laid rigidly for all categories For this category, a hydraulically bound road base should be used and should be designed in accordance with the relevant standard (see above).
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TECHNICAL INFORMATION: charcon.technical@aggregate.com
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