Roof waterproofing Method statement

ROOF WATER-PROOFING

1.0 OBJECTIVE

1.1 Is to define the requirements for laying of roof water proofing membrane for the contract no GTC.101/ED/01 Engineering, Procurement, Installation and Commissioning (EPIC) of Ras Laffan Utilization Project –Buildings and utilities and support service Phase 1-Utilities.

2.0 SCOPE

2.1 Water and thermal proofing of roof of buildings in Service Base Area, Service     Berth area and F.S.O Marine.

3.0 REFERENCE

• Project Approved Drawings
  • British Standards BS 747, 882, 812
  • Qatar Construction Specification-Section 14
  • Product Manufacture’s specification

4.0 PROCEDURE:

4.1 APPROVAL OF MATERIALS:

• Approval shall be taken from QP for the materials – Bitumen primer, Water proof membrane, Extruded Polystyrene insulation boards, terram geo textile membrane, Geo textile water filtering membrane, Aluminum flashing, external quality Sealant, Rubber bitumen joint sealant, PC tiles, Gravel/aggregate etc prior to commencement of roof waterproofing work:.

• Sample of all the materials shall be available at site for QP verification/reference at all times.

4.2 SURFACE PREPARATION:

• The deck should be dry enough that no dampness or moisture on the surface.

• Sweep decks and remove all dust, dirt and debris.

• Remove projections that might penetrate or damage roofing felt materials.

• Test concrete decks for moisture prior to application of roofing materials by pouring heat bitumen on surface (approximately 0.5 liters per sq. m) to which roofing material are to be laid. If bitumen foams upon the concrete or if the bitumen after cooled is stripped from deck leaving no residue, the deck is not dry enough for application of prime coat/water proofing.

• Approval shall be taken from QP engineer for surface preparation prior to  application of bitumen primer.

    4.3 APPLICATION OF WATERPROOFING:

• Once the surface preparation is approved, apply the approved Bitumen primer as per manufacturer’s specification. There should not be any flooding/recess while applying the primer. The application shall be uniform and cover entire area.

• Allow primer to dry before application of bitumen membrane

• Before start fixing the water proofing membrane, inform QP engineer about the activity and call for witnessing the fixing.

• Check the water proofing membrane for free of wrinkles, blisters, bubbles, voids air pockets or other defects that prevent complete adhesion.

• Fix/lay the roll of water proofing membrane to the primed surface by means of heating / torching and fixing or as per manufacturer’s specification.

• Felts shall be lapped a minimum of 100mm single fashion starting with starter strips at right angles to slope of roof. The laying of the roofing materials shall commence at the low points.

• Membrane shall extend to height of minimum 150 mm along the vertical surfaces of parapet, walls and other standups.

• Cut the felt to fit closely around pipes, roof drains and similar roof projections.

    4.4 FLOODING TEST AND LAYING OF THERMAL INSULATION:

• Flooding test shall be conducted to ensure that the waterproofing has been done effectively.

• Close all the drainage outlets by means of temporary arrangement and fill water for at least 50 mm above the membrane on the highest point of the roof.

• Inform QP regarding the flooding of roof for testing.

• Allow the water to stand for at least 24 hours.

• Check for any leakage, dampness underneath the flooding area of the building. If any such thing noticed, drain the water, allow the roof to dry completely, rectify the defects in laying of membrane and again conduct flooding test. If it is found satisfactory, request for QP inspection and approval.

• Over the approved water proofing membrane, lay terram geo-textile membrane and over that lay 50 mm extruded polythene insulation.

• Over the polystyrene insulation, a layer of geotextile water filtering membrane shall be laid.

• Upon the geo textile water filter, lay Plain Concrete tiles 50 mm thick or clean and washed crushed white/pale grey rounded gravel to comply with requirement of BS 882, of size 15 to 30 mm free of all impurities, to a thickness of 50 mm to be laid. Rounded gravel shall be free of sharp angular or broken pieces

• Approval shall be taken from the QP Engineer for the laying of thermal protection.

• Aluminum flashing is to be fixed along the parapet wall. The height of flashing to be as per drawing. The top edge of flashing is to be recessed into plastering and rubber bitumen joint sealant is to be filled. The joint between flashing and PC tiles is to be filled with approved sealant.

• Provide expansion joints filled with sealant for PC tiles as shown in the drawings.

    5.0 GENERAL:

• The roof coverings are not to be applied to a damp base and care is to be taken to ensure that no moisture is trapped between successive layers.

• Protective finishes and surface treatments are to be applied as soon as possible after completion of the roof coverings.

• Projections passing through the roof covering are to be provided with hoods or caps to permit the roof covering to terminate beneath the hood and be protect it from weather elements.

• Outlets for surface water, gutters or roof areas, are to be set slightly below the adjacent roof surface and be suitably flashed to allow a bonded lap of roofing felt and flashing material of 100mm (minimum)

• Roofing materials shall not be applied if the deck will be used as a subsequent work platform for storage of materials or if staging or scaffolding will be erected thereon.

• The entire roof deck construction of any section of the building is to be completed before water proofing work is begun.

• Roofing materials are to be dry when applied.

• Roof water proofing materials shall not be applied during damp or rainy weather, during excessive wind conditions or while moisture (dew or fog) is present in any amount in or on the materials to be covered or installed.

•  Materials shall not be applied when the temperature is below 10 C.

• Phased construction is not permitted.

    6.0 RECORDS:

• Inspection Reports

• Check list