1. Building site appraisal
Its impact on the design of a
building

2. Site appraisal
• All building sites are different
• The site for a new building needs
to be thoroughly appraised
• Appraisal generally follows a two
stage process:
1. Desk top appraisal
• Find out everything that is documented
about the site, before visiting it
2. Physical site appraisal
• Direct investigation of the site itself

3. Desk top appraisal
• Site location
– Geography
• Elevation
• Slope
• Aspect
• Flood risk
– Climate
• Temperature range
• Wind direction and
strength
• Insolation (solar
energy)
• Rainfall

4. Site specific problems: e.g. wind direction related to orientation

5. Sources of location information
• Ordnance survey maps, current and
historical
– Gives topographical information such as
height, slope, relation of site to roads and
rivers
• Environment agency maps of flood risk
• Meteorological office for local climate
information
• Local authority map
collections for
geological maps,
soil maps, zoning
maps, local area plans

6. External influences on a building site
• Covenants and easements
– Rights of way
– Rights to light from neighbouring properties
– Rights of access
Typical inner city
– Leasehold restrictions underground
• Services service plan
– What’s under/over
the site?
– What’s near
the site?
– What’s far
from the site?

7. On completion of desk top appraisal…
• You will have studied many
documents and maps
• You will have consulted many
legal, statutory and service
providing organisations
• You should now have a knowledge
of all of the external influences on
the site
• Now you need to get on the site
itself.

8. Physical site appraisal
• First, measured site survey
– To determine its true size and extent
– To identify ill defined boundaries
– Never rely on published documents
for this information
• Direct site inspection
– Checking for signs of previous
development (bricks and tiles on the
surface are indicative)
– Checking for unmapped risks such as
springs

9. Wind farm site on apparently undisturbed farmland
There will be power cables somewhere under this land

10. Building site in Berlin, 1,000 years of development & disturbance

11. Sub-surface inspection: Trial holes
• Dig a hole: a trial hole or
inspection pit
• Can be dug by hand, but more
economic to hire a digger
• Max depth 2 metres
• More than one hole should be
dug on a site
• Very dangerous to get in the hole
Proposed
building Site
boundary
Trial hole

12. What are you looking for in a trial hole?
• Depth of top soil and nature of
sub-soil
– Clay, potential problems.
– Sand, potential problems.
– Gravel, fairly reassuring.
• Signs of disturbance from previous
building
• Level of water table
• Soil samples for testing

13. Trial hole results
• Soil samples for testing can be
taken for
– Chemical analysis
– Structural testing
• Maximum realistic depth is about 2
metres
• If you are not satisfied that there
is a suitable bearing layer in the
depth of the trial hole, then
boreholes are needed.

14. Boreholes: expensive but reassuring
• No practical limit to
depth
• Drilled in a grid
across the site
• Core samples taken
right down to
bedrock
Old buried landfill, not
detected by trial holes

15. Borehole record
• Record for each
borehole
• Gives depth and
nature of every
soil encountered
• Variation in depth
of underground
strata can be
interpolated right
across the site

16. Completion of site appraisal
• On completion of desktop and
physical appraisal you should know
– Exact size and shape of site
– Previous history
– Reasonable knowledge of subsurface
conditions
– All service restrictions
– All legal constraints
– All special risks such as flood or
contamination
• You are ready to start designing