Firemen's Cottages Flashcards
In Construction Technology, you mention the following - can you tell the costs, duration, and how measured the following
Cracks
Subsidence (underpinning)
Foundation types
You specifically mention putting together costs for the following, please explain:
Underpinning foundations and reinstatement
Cracks (Allowance for crack repairs such as opening up and patching; repointing; brickwork replacements; breaking-out and replacing sections of walls (particularly around windows and doors); helibar repairs.
-Items in photos - measure and cost
-General allowance, brick replace and repairs, £40k (in-house; based on general area 500m2)
Subsidence (underpinning):
Depth of 2.2m (external) - £5k (10lm, £200/m2)
Depth 1.8m (internal) - £5k (15lm, £150/m2)
SPONS - description and cost: UNIT m2
In stages not exceeding 1500mm long from one side of existing wall and
foundation, excavate preliminary trench by machine and underpinning pit by
hand, partial backfill, partial disposal, earthwork support (open boarded), cutting
away projecting foundations, prepare underside of existing, compact base of pit,
plain in situ concrete 20.00 N/mm² – 20mm aggregate (1:2:4), formwork,
brickwork in cement mortar (1:3), pitch polymer damp-proof course, wedge and
pin to underside of existing with slates Commencing at 1.00m below ground
level with common bricks, depth of underpinning
900mm high, one brick wall m2 370.00 to 445.00
1500mm high, one brick wall m2 530.00 to 640.00
Extra for excavating commencing
2.00m below ground level m2 72.00 to 88.00
3.00m below ground level m2 140.00 to 170.00
4.00m below ground level m2 200.00 to 240.00
Foundations - didn’t mention this!!
Underpinning (inc access and reinstatement)
NRM 1, page 103:
UNIT - LM; ‘Details to be stated.’
1 Underpinning to external walls
adjoining the new building.
2 Underpinning to walls within
existing buildings, which are to be
rehabilitated (i.e. internal walls).
3 Preliminary trenches and
underpinning pits, excavation
and earthwork support.
4 Temporary supports.
5 Disposal of excavated material,
including tipping charges and
landfill tax (including inert,
non-hazardous and hazardous
material where not to be carried
out as facilitating works).
Note: where no contamination/
remediation strategy report
exists, an allowance is to be
made within the construction
risk allowance for the extra cost
of disposing of contaminated
material.
6 Cutting away existing projecting
foundations, etc.
Underpinning (website) -
Continuous Underpinning of Strip Footings – Pit Method
This method is also referred to as pier underpinning, pit underpinning, and pit pier.
Sometimes it is called as mass concrete underpinning method too.
This method is widely used to improve the foundation under the brick walls.
Here the failure does not mean collapse but it is starting the cracks in the building or in the referred structure due to the settlements.
The following procedure is followed in this method.
Firstly, pits are excavated under the foundation at regular intervals.
The spacing of the pits could be 1-2m depending on the condition of the brick wall. If the quality of the brick is very poor, this spacing could not exceed 1.0m.
Further, the spacing of the pits is determined from the arching action of the brick wall over the pit.
Pit walls could be supported with timber as required.
Depth of excavation could be done according to the soil conditions. Excavations are usually terminated at a soil layer that having the required bearing capacity.
Then the pit will be filled with mass concrete.
If other materials such as brickwork, masonry or precast concrete blocks, etc are used they shall be used with cement mortar.
The final gap between the fill and the foundation (50-100mm) could be filled with a strong mix like 1:3 cement: sand.
Process of underpinning (Chat GPT):
Obtain necessary permits and approvals from local authorities.
Excavation:
Dig inspection holes to assess the depth and condition of the existing foundation.
Excavate small sections (underpins) beneath the existing foundation in a sequence to avoid undermining the wall. Typically, sections are 1-1.5 meters wide.
Installation of Underpins:
Place reinforcement bars (if required) within the excavated section.
Pour concrete into the excavated section to create the new underpin. Allow it to cure and gain strength.
Repeat Process:
Continue the process in a phased manner, ensuring each section cures before excavating adjacent sections.
Backfilling:
Backfill the excavated areas with suitable material and compact it properly.
Cracks
NRM 1 pg 303, 7.6.1 Masonry repairs; ‘details to be stated’ UNIT nr/m/m2
1 Cutting out decayed, defective
and cracked bricks, blocks
or stones and inserting new
(including isolated repairs,
stitching, etc.).
2 Plastic stone repairs.
3 Re-dressing stonework
to new profiles.
4 Inserting new wall ties (without
demolition).
5 Grouting.
6 Rejointing/repointing existing
masonry.
7 Sundry items.
8 Where works are to be carried
out by a subcontractor, the
subcontractor’s preliminaries,
design fees, risk allowance,
overheads and profit, with
allowance for these to be
made within unit rate applied
to element or component.
Concrete Repairs
NRM 1, pge 304; 7.6.2; ‘details to be stated’; UNIT nr/m/m2
Cutting out defective concrete
and replacing with new.
2 Cutting out defective
reinforcement and
replacing with new.
3 Cleaning and rust proofing
existing rusted reinforcement.
4 Concrete and resin/cement
mixes in repairs and resurfacing,
including spray-applied concrete.
5 Anchored mesh reinforcement.
6 Resin or cement impregnation/
injection.
7 Sundry items.
8 Where works are to be carried
out by a subcontractor, the
subcontractor’s preliminaries,
design fees, risk allowance,
overheads and profit, with
allowance for these to be
made within unit rate applied
to element or component.
Timber repairs
NRM 1, pg 306; 7.6.4; ‘details to be stated’; UNIT nr/m/m2
1 Taking down existing work,
cleaning and resurfacing, cutting
out defective or decayed timber,
piecing-in new timber, rejointing
and refixing.
2 Resin repairs to timbers.
3 Preservative/fire-retardant
treatments.
4 Repairs to structural
members (e.g. roof members
and structural beams).
5 Repairs to existing windows,
doors, hatches, rooflights, frames,
linings, etc. (including overhauling/
renewing ironmongery, sash
cords, opening gear, etc.).
6 Repairs to staircases, including
handrails and balustrades.
7 Sundry items.
8 Where works are to be carried
out by a subcontractor, the
subcontractor’s preliminaries,
design fees, risk allowance,
overheads and profit, with
allowance for these to be
made within unit rate applied
to element or component.
In DECP, you mention developing an order of cost estimate - what was the estimate value at this stage?
While preparing this OoCE, you mentioned it comprised ‘elemental rates at high level’ - so the estimate wasn’t based on generic GIFA m2 or Function Unit? If not, did you have enough information to do a take-off? If so, why would this not be a Cost Plan rather than an Order of Cost Estimate?
Can you tell me some of the categories of costs and their associated elemental rates at high level? Where did you obtain these rates from?
£900k Base Cost Limit of 2nd OoCE (RIBA STAGE 0 - rough OoCE for client develop business case - not at the stage of developing the full scope of works yet (this is at RIBA Stage 1 - the scope of works is defined and the cost limit identified (ref the NRM Flashcards))
Estimate was mixture of GIA (M&E) but also approximate quantities based on sketches and photos within Feasibility Report (feasibility report mentions many other reports to follow - these were also factored into the ‘rough’ OoCE)
This was still an estimate as it was based on preliminary information of works required but also possible works - these possible works were subject to later reports to be issued.
Cost categories (and where obtained rates):
Substructure - underpinning (costs and details in earlier flashcard)
Superstructure :
Roof replace £130k + £30k top hat + above over for decanting (not inc’d in construction costs) - quote
Allowance for external repairs to roof including replace fascias/soffits - £20k
Allowance patch repairs timber roof - £20k
Fire compartmentation £40k
Repair chimney £14k (7nr, £2k/chimney)
-Lighting installations - supply and install emergency lighting within communal areas and loft space £6k (2 communal areas, £3k/area)
-Lighting installations - supply and install emergency lighting to rear emergency exits into the courtyard £4k (4 nr, £1k/nr)
-Supply and installation of doorbells [intercom system] to serve each of the 8 nr flats. £1.5k [3k]
-Repairs underground drainage £10k allowance
-garden clear up £2k
Upgrade paving £5k
upgrade landscaping £10k
-
In DECP (continued), can you tell me in precise detail how many OoCEs and Cost Plans you produced, the estimated costs for each, what changes were made resulting in changing costs from estimate to estimate, the information/additional information obtained from one estimate to the next? How each estimate (OoCE/Cost Plan) mentioned above correlates with each of the RIBA stages (at what stages of the RIBA was each estimate produced)?
What was the final breakdown of costs for the final estimate ie building works, preliminaries, OHP, PSUMs, Risk Allowances?
OoCE1 AND OoCE2??? - value, RIBA 0 (Strategic Definition AND Preparation and Brief), rough. info - developed with very limited information ie feasibility survey conducted just to get estimate of works required to repair structural damage, essential repairs and upgrades (windows and doors), fire upgrade (compartmentation; flat doors), make good.
Facilitating works £24,000 (diversions; asbestos)
Substructure £50,000 (SE site visit, possible works for underpinning)
Superstructure £453,000 (roof; cracks; wind/door)
Internal finishes £36,000 (communal upgrade)
Fittings, furnishings and equipment £0.00
Services £0.00
Complete buildings and building units £0.00
Work to existing buildings £0.00
External works £15,000
Preliminaries £151,000 (based on 15%)
Overheads and Profits £55,000 (based on 8%)
Total: Building works estimate £784,000
PROJECT FEES (based on %/GIA 860m2) £123k
Cost Limit ——£907,000———
RISK (based on 10%/GIA 860m2) £75k
INFLATION (TPI adjustment) £0 (excluded)
TOTAL ALL IN COST —–£982,000—–
OoCE2 (OR Cost Plan 1??? RIBA 1 (Preparation and Brief)), scope finalisation, cost limit identified. info - client confirmed to proceed with investigations (structural) and update estimate. During this stage, if structural damage to roof only required repair then determine what repairs and the costs. If estimate still allows at this stage, include estimates for other surveys ie retrofit survey (improvements to thermal efficiency eg insulated render).
Facilitating works £24,000 (as before)
Substructure £31,000 (down - underpinning works firmed but still estimate)
Superstructure £373,000 (down - repairs instead of replace roof)
Internal finishes £36,000 (as before)
Fittings, furnishings and equipment (as before)
Services £41,000 (up - now works added)
Complete buildings and building units £0.00
Work to existing buildings £0.00
External works £15,000 (as before)
Preliminaries £151,000 (adjusted)
Overheads and Profits £55,000 (adjusted)
Total: Building works estimate £726,000
PROJECT FEES (based on %/GIA 860m2) £123k (adjusted)
Cost Limit ——£849,000———
RISK (based on 10%/GIA 860m2) £75k (adjusted)
INFLATION (TPI adjustment) £0 (excluded)
TOTAL ALL IN COST —–£924.000—–
Cost Plan 1 - value, where changed, RIBA 2, Concept Design - scope and cost limit has been set ie £1,000,000. info - all scope items ie structural; retrofit; fire; essential repairs and upgrades; services; AND NOW: further upgrades to services; more external works (landscaping, paving); loft space reconfiguration - now to be considered for development of costs to within the cost limit of £1,000,000.
Final breakdown of cost:
Facilitating works 24,000 (as before)
Substructure 31,000 (as before)
Superstructure 400,000 (up - loft)
Internal finishes 40,000 (up - loft)
Fittings, furnishings and equipment 0.00
Services 50,000 (up - loft; intercom)
Complete buildings and building units 0.00
Work to existing buildings 0.00
External works 25,000 (increased)
Sub Total: Building works £570,000
Preliminaries £151,000 (based on 15%)
Overheads and Profits £55,000 (based on OHP)
Total: Building works estimate £776,000
PROJECT FEES (based on estimate) £123k
Cost Limit ——£899,000———
RISK (based on Risk Register ie ground works; structural works identified post contract; condition of masonry following render removal; resident issues; ……?) £75,000
INFLATION (TPI adjustment) £0 (excluded)
TOTAL ALL IN COST —–£974.000—–
In DECP, you mention roof estimate for removal - how did you measure and cost for this? What was the cost?
How did you adjust costs ‘as necessary’ ie what costs were adjusted and why? [ref categories of costs below!!]
You mention, savings reallocated to other elements of building works - what other elements/how did you measure and obtain costs for the following - stated as:
- spot repairs to:
- roof structure,
- covering,
- chimney,
- improving ventilation,
- fire compartmentation,
- reconfiguration of existing loft spaces
- upgrading quality of works,
- upgrading quality of specifications
Why the above elements? What were the total costs for each of the above?
Roof removal:
-above ie quote; £130k inc £30k top hat + decanting (below line)
-
-
Adjustments:
Reference my earlier flashcard (commentary and changes in breakdowns)
Note: This reallocation of works is part of defining the scope of works? - therefore, this is an OoCE is it not? And a rough one at that ie RIBA Stage 0?: - could say the scope of works was defined however there was large scope for flexibility ie if roof not require replacing then the retrofit survey/recommendations would go ahead to full extent?
New (reallocated works):
spot repairs to:
-ref earlier flashcards.
One of the survey reports was a Retrofit Report - works relating to improving the thermal properties of the property and (upgrading facilities??). The area in the attic was identified an recommended for renewal (or maybe another report? - no! - this was part of the building surveyors brief and they developed the design along with myself) Feasibility - noted attic, making good, but not bringing back in to use).
In Risk, you mention risk value of replacing entire roof and decanting residents - please explain how you developed the costs - measured, rates, etc?
How did you ‘apportion’ the above costs ‘as necessary’?
How was scope of works reduced and then the Contingency cost ‘adjusted accordingly’ following confirmation that roof did not need to be replaced?
How was the Contingency Sum established in the first place on this project?
Risk allowance for Roof:
- ref flashcard above
Apportion costs:
-ref flashcard above
Contingency cost adjusted accordingly:
-this was at high level stage where % allowance was still being applied for risk. (NRM Flashcards - Risk Register kicks in at Cost Plan 2?).
