Show and tell
1
BIM BIM BIM BIM BIM BIM BIM BIM RICS PROPERTY JOURNAL 14 MAY/JUNE 2014 UPFRONT RICS HQ BIM Les Pickford is a freelance editor and journalist [email protected] Continuing his series following the RICS BIM project at Parliament Square, Les Pickford looks at a software vendor showcase that compared how different software packages extracted quantities from the RICS model Show and tell B uilding information modelling (BIM) will mean a change of approach and new challenges for construction professionals, says James Fiske, RICS Director of Delivery and Operations. “For example, taking quantities directly from a model means that its quality is critical, particularly component naming and coding.” To understand this area more, RICS held a software vendor showcase that challenged four suppliers to use the BIM model in place at its headquarters and to extract quantities typically required for early-stage construction estimates, e.g. gross internal floor area (GIFA) and elemental unit quantities. RICS wanted to understand: b how easily software could take off quantities b the challenges faced and the assumptions made b vendor results compared to RICS-supplied ‘tape measure’ figures b the consistency of results between the vendors b how much checking of outputs was required b considerations for BIM of existing buildings. The main finding was the wide variances in extracted quantities between vendors (see Figure 1). Using GIFA and a newbuild cost of £4,000/m 2 , the difference in cost estimates was £5m. The original brief for the laser scan was to provide walk-throughs for events, and it was only later that other uses were considered. That made the model a tough test for tools aimed primarily at newbuild projects. “I think this was mainly due to an incomplete model, because surveyors could not scan all areas during office hours, for example the restaurant,” suggests Paul Burrows, a Solutions Architect at BCIS. “All vendors were given full computer-aided design [CAD] floor plans and copies of the building’s original 1898 drawings, but only one used this. Its floor area calculation was within 50m 2 of ours.” Burrows summarises the other findings as: b models for existing buildings will rely much more on human skill and interpretation, and assumptions about what the model ‘means’ b cost planning objects NRM1: Order of cost estimating and cost planning for capital building works are not included as standard in Revit (which created the model) and so modellers did not classify against this list. This has implications when construction professionals later procure building works (NRM2) and manage facilities (NRM3) b two vendors revisited the original 3D model because they did not trust Industry Foundation Classes (IFC) outputs. This was not a criticism of IFC, more that applications do not output IFC consistently. “The showcase provided useful pointers for developing our model, including quality standards and valid or invalid assumptions to make,” says Burrows. His advice for others considering BIM is: b models for existing buildings (using scanned laser surveys) will be very different from a newbuild model because they lack structural detail b do your own evaluation using your most experienced estimators against two models (new and existing buildings) b ask how the software supports your professional judgment in your normal tasks. Is it easy to navigate and spot problems? Can you make corrections and apply your assumptions? b understand different vendor approaches, e.g. overseas design and procurement practice can be very different from the UK (involving architects, quantity surveyors and contractors). “The importance of a quantity surveyor’s professional judgment is highlighted when making sense of a model,” says Burrows, “especially one for an existing building that was created by scanning and importing the data.” b For more details of the Showcase, visit www.rics.org/bim Related competencies include: Data management Figure 1 The variances in element unit quantities between vendors -60% -40% -20% 0% 20% 40% 60% RICS result Vendor results Key Floor finishes Ceiling finishes Fittings, furnishings and equipment Substructure Frame Upper floors Roof Stairs and ramps External walls Windows and external doors Internal doors Wall finishes Internal walls and partitions Services
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Continuing his series following the RICS BIM project at Parliament Square, Les Pickford looks at a software vendor showcase that compared how different software packages extracted quantities from the RICS model
Transcript of Show and tell
BIMBIMBIMBIMBIMBIMBIMBIM
RICS PROPERTY
JOURNAL
1 4 M A Y/J U N E 2 0 1 4
UPFRONTRICS HQ BIM
Les Pickford is a freelance editor and [email protected]
Continuing his series following the RICS BIM project at Parliament Square,
Les Pickford looks at a software vendor showcase that compared how
different software packages extracted quantities from the RICS model
Show and tell
Building information
modelling (BIM)
will mean a change
of approach and
new challenges
for construction
professionals, says
James Fiske, RICS Director of Delivery
and Operations. “For example, taking
quantities directly from a model means
that its quality is critical, particularly
component naming and coding.”
To understand this area more, RICS
held a software vendor showcase that
challenged four suppliers to use the BIM
model in place at its headquarters and
to extract quantities typically required
for early-stage construction estimates,
e.g. gross internal floor area (GIFA) and
elemental unit quantities. RICS wanted
to understand:
b how easily software could take
oW quantities
b the challenges faced and the
assumptions made
b vendor results compared to
RICS-supplied ‘tape measure’ figures
b the consistency of results between
the vendors
b how much checking of outputs
was required
b considerations for BIM of
existing buildings.
The main finding was the wide variances
in extracted quantities between vendors
(see Figure 1). Using GIFA and a newbuild
cost of £4,000/m2, the diWerence in
cost estimates was £5m. The original
brief for the laser scan was to provide
walk-throughs for events, and it was only
later that other uses were considered.
That made the model a tough test for
tools aimed primarily at newbuild projects.
“I think this was mainly due to an
incomplete model, because surveyors
could not scan all areas during occe
hours, for example the restaurant,”
suggests Paul Burrows, a Solutions
Architect at BCIS. “All vendors were
given full computer-aided design [CAD]
floor plans and copies of the building’s
original 1898 drawings, but only one used
this. Its floor area calculation was within
50m2 of ours.”
Burrows summarises the other
findings as:
b models for existing buildings will
rely much more on human skill and
interpretation, and assumptions about
what the model ‘means’
b cost planning objects NRM1: Order
of cost estimating and cost planning for
capital building works are not included
as standard in Revit (which created the
model) and so modellers did not classify
against this list. This has implications
when construction professionals later
procure building works (NRM2) and
manage facilities (NRM3)
b two vendors revisited the original
3D model because they did not trust
Industry Foundation Classes (IFC)
outputs. This was not a criticism of IFC,
more that applications do not output IFC
consistently.
“The showcase provided useful pointers
for developing our model, including
quality standards and valid or invalid
assumptions to make,” says Burrows. His
advice for others considering BIM is:
b models for existing buildings (using
scanned laser surveys) will be very
diWerent from a newbuild model because
they lack structural detail
b do your own evaluation using your
most experienced estimators against
two models (new and existing buildings)
b ask how the software supports your
professional judgment in your normal
tasks. Is it easy to navigate and spot
problems? Can you make corrections
and apply your assumptions?
b understand diWerent vendor
approaches, e.g. overseas design
and procurement practice can be
very diWerent from the UK (involving
architects, quantity surveyors and
contractors).
“The importance of a quantity surveyor’s
professional judgment is highlighted
when making sense of a model,” says
Burrows, “especially one for an existing
building that was created by scanning
and importing the data.” b
For more details of the Showcase, visit www.rics.org/bim
Related competencies include: Data management
Figure 1The variances in element unit quantities between vendors
-60% -40% -20% 0% 20% 40% 60%
RICS result
Vendor results
Key
Floor finishes
Ceiling finishes
Fittings, furnishings and equipment
Substructure
Frame
Upper floors
Roof
Stairs and ramps
External walls
Windows and external doors
Internal doors
Wall finishes
Internal walls and partitions
Services
