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Overall building costs
听	听	Steel frame & composite composite decking	Steel frame & precast concrete floor	Steel frame and slimdek
听	£/m2	£1,488.72	£1,487.02	£1,558.11
In situ concrete post-tensioned flat slab and columns	£1,459.00	2.00%	1.90%	6.80%
In terms of overall construction costs, the steel-framed options were found to be between 1.9% and 6.8% more expensive than the most economic concrete-framed solution, the post-tensioned flat slab.

Breakdown of costs
听	In situ concrete 2-way flat slab & columns	Precast concrete floor & in situ frame	In situ concrete post-tensioned flat slab & columns	Steel frame & composite decking	Steel frame precast concrete floor	Steel frame & slimdek
听	£/m2	£/m2	£/m2	£/m2	£/m2	£/m2
Substructure	63.07	60.91	60.97	57.6	59.2	57.51
Frame and upper floors	133.81	134.41	121	122.32	111.62	197.26
Roof	133.81	82.75	82.75	82.75	82.75	82.75
Stairs	18.56	18.56	18.56	18.56	18.56	18.56
External envelope	247.1	256	240.91	255.5	261.77	250.51
Internal planning	78.91	81.97	78.15	86.04	86.1	82.31
Finishes	110.65	112.47	110.78	109.7	109.95	109.13
Fittings	109.99	109.99	109.99	109.99	109.99	109.99
Services	338.41	338.41	338.41	344.11	344.11	338.41
Preliminaries, contingency, O/H&P	305.22	304.57	297.48	302.15	302.97	311.68
Total	£1,488.47	£1,500.04	£1,459.00	£1,488.72	£1,487.02	£1,558.11

Internal planning costs
听	听	Steel frame & composite composite decking	Steel frame & precast concrete floor	Steel frame and slimdek
听	£/m2	£86.04	£86.10	£82.31
In situ concrete post-tensioned flat slab and columns	£78.15	10.10%	10.20%	5.30%
Internal planning costs, comprising internal walls and doors, were found to be between 5.3% and 10.2% more expensive on the steel-framed options than on the concrete-framed option with the lowest floor-to-floor height, the post-tensioned flat slab. The flat soffits that are provided by precast concrete planks or in-situ concrete formwork will be easier to finish internal partitions against. Conversely, providing an acoustically “robust” head detail of an internal wall against a profiled deck or steel down-stand beam can be far more time consuming, both in initial installation and in subsequent re-work. Account is therefore taken of the added complexity of fire and acoustic sealing of partition heads against the irregular soffits of the steel decking and around the junctions of intersecting steel frame members. With approximately 3,000 linear metres of internal partitions, this is a significant factor.

External envelope costs
听	听	Steel frame & composite composite decking	Steel frame & precast concrete floor	Steel frame and slimdek
听	£/m2	£255.50	£261.77	£250.51
In situ concrete post-tensioned flat slab and columns	£240.91	6.10%	8.70%	4.00%
External envelope costs, representing 17% of the total project value and comprising cladding, windows and external doors, were found to be between 4.0% and 8.7% more expensive on the steel-framed options than on the concrete-framed option with the lowest floor-to-floor height, the post-tensioned flat slab.