Basement Construction

Basement Construction

1. Grades

   • Grade 1
     • Basic Utility - Car Park
   • Grade 2
     • Better Utilitiy - Storage, Elec plant
   • Grade 3
     • Habitable - Offices, kitchen
   • Grade 4 (EU only)
     • Special - archives
   • BS8102:2009
   • Why Grades?
     • enviro conditions
     • insulation
     • ventilation
     • moisture control
     • humidity
     • temperature

2. Design Considerations

   • structural stability
     • forces exerted from building above to ground
   • durability
     • agressve nature of sub-soils, chemicals, groundwater
   • moisture exclusion
     • pressure of ground water (hydrostatic)
   • buildability
     • excavation, ground retention, access

3. Waterproofing

   • similar properties to 'retaining walls'
   • dependant on Grade
   • Water Table
     • High - Above BF
     • Low - below BF
     • Variable
   • BS8102:2009
     • Membraned
     • Monolithic
     • Drained cavity
   • Systems
     • Bonded sheet membrane
       • bonded hot / cold
     • Cavity drained membranes
       • High density rigid sheet - internal
     • Bentonite clay active membranes
       • swells to seal gaps / between cardboard layers
     • Liquid applied membranes
       • epoxy, polymer or bitumen
     • Mastic asphalt membranes
       • multi layer appl
     • Cementitious crystallisation active systems
       • slurry appl - reaction with concrete / seals gap
     • Cementitious renders
       • int appl coating with waterproofing admixture

4. Construction

   • Shallow
     • most basements
     • angle of slope 'repose' for soil
     • risky with non-cohesive soil and high levels of mobile ground water
   • Deep
     • types
       • Contiguous Piles
         • adjoining
         • bored replacement piles
         • form basement enclosure
         • lined internally with WP
       • Secant
         • similar to contiguous but interlocking
         • male and female piles
         • smaller diam than contig
       • Diaphragm Walls
         • constructed in panels btwn guide walls (sheet piles) then built in masonry (wider walls)
         • depth - 20 to 30m
         • Bentonite commonly used
     • temp support
     • cost - excavate & dispose materails
     • groundwater & dewatering
   • Bottom up
   • Top Down
   • Factors
     • nature of site
       • access
       • topography
       • water table / drainage
     • Building form
       • structural form
       • depth of basement
       • function
     • Legal issues
       • rights of adj owners
       • H&S
     • Economic issues
       • max potential
       • min cost

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