Method of Statement for Substructure Waterproofing works
Scope of Works.
The purpose of this method statement is to outline the materials and labor required to undertake the Substructure Waterproofing works in safe and controlled manner, compiling with relevant legislation, Standards and Codes of practice etc.
The method statement shall be briefed to all appropriate operatives to ensure that they are aware of the sequence of activities and any Client/Consultant project specific requirements.
A constant monitoring and supervision duty shall be undertaken by waterproofing subcontractor to ensure work activities are carried out in accordance with the method statement. Any irregularities shall be immediately actioned.
The method statement describes the working procedures for Substructure waterproofing works including all related activities.
Execution.
SURFACE PREPARATION OF PILE HEAD:
- Break weak concrete layer of pile head top face until solid/sound concrete is reached.
- Wire brush concrete surface to remove the weak concrete laitance.
- Using clear portable water, thoroughly clean the pile head top face.
PILE HEAD TREATMENT:
- Repair Pile head top face using high strength non-shrink
cementitious grout.
- Extend the Double layer of 4mm thick waterproofing membrane
over the pile head sides and top face, up to the reinforcing bars limit.
- Seal top face and side of pile head by casting
of high strength epoxy grout 30mm thick.
HORIZONTAL SURFACE OVER CONCRETE BLINDING :
Concrete blinding dry, clean, smoothly finished protrusions/
depressions and cracks free (if existing; suitably treated), 100mm minimum
thickness.
Primer:
The concrete surface shall be primed using solvent based bituminous primer conforming to ASTM D-41 and left to dry (1-2 hours depending on prevailing weather condition).
Waterproofing Membrane:
- Install Double layer of 4mm thick SBS modified bituminous membrane reinforced with 180g/m2 non-woven polyester.
- Unroll and position the membrane roll. Roll out half a roll length, heating the underside of the membrane with the gas flame until the polyethylene film and bitumen mass melts.
- Unroll the membrane steadily and continuously. A bead of liquid bitumen must be visible on the
- underside of the roll. The torch on membrane must be firmly pressed onto the substrate in order to
- avoid air entrapment using a roller or heavy brush.
- Repeat this procedure with the second half of the roll.
- The membrane shall be torch applied loose laid with 100mm wide overlaps.
Protection Screed.
VERTICAL AREAS OF RETAINING WALL:
Base:
External Face of Structural walls, beams, dry, clean and
smoothly finished.
Surface Preparation:
- Defective concrete spots (segregation, hollows, honeycombs, cracks, protrusions, etc.…) must be suitably treated with proper repair material prior to commencement of waterproofing works.
- Edge lines must be slightly chamfered to avoid membrane application over sharp edges.
- Clean the concrete substrate by brooming or compressed – air from dust/sand and use hand or
- mechanical grinding to remove any cement spot residues, to allow for proper membrane adhesion.
- Concrete strip lines caused by wood shutters must be removed by mechanical grinding and made smooth leveled.
- Make 30x30mm mortar cannot strip at junction lines between horizontal and vertical surface.
Primer
The concrete surface shall be primed using solvent based
bituminous primer conforming to ASTM D-41 and left to dry (1-2 hours depending
on prevailing weather condition)
Waterproofing Membrane
- Ditto as in horizontal areas, using the SBS Double layer waterproofing membrane, torch applied system.
- The waterproofing membrane shall be extended minimum100mm above finish.
- The membrane shall be torch applied with 100mm wide overlaps.
Protection
Board:
The vertically applied waterproofing membrane shall be
protected with 6mm thick “Sika Protection Bituminous protection board spot
bonded with 30mm wide overlaps.
TERMINATION OF WATERPROOFING MEMBRANE
The upper end of the waterproofing membrane shall be
terminated by using Aluminum Flashing 1x50mm and sealed with bituminous mastic
sealant.
See Risk Assessment Template for Substructure Waterproofing Work.