In reality, if you are a salary employee, your prelim allocation, and any associated internal cost-coding, should be done by the commercial team. But as we move into the world of moving away from the days of risk-free day working explained simply, as just not being self-employed due to carrying no real “profit/loss” risk or accountability, as you would be paid no matter what, and were instructed the same way as employees, you couldn’t turn down any deliverables otherwise you were let-go/sacked.

Hence why things have changed for the better with IR35, (If you go direct it is easier if you are set up correctly as a business, a little more complicated agency wise, but you can still keep legally-aligned, via an all-in "profit/loss basis" - fixed fee, with a payment application system of practise, or alike - plus say goodbye to the umbrella company commissions in addition).

This is rightly and fairly so, as it aid's in draining out chancers, it just doesn't work out very well for agencies, unless they were able to add their commission onto your fixed price, but then although the client gets a fixed-price for costing purposes (This would have the benefit of being, an "all-in/risk free" fixed price, for forecasting purposes), it would/could by default be too expensive, so the client would likely go/sell it elsewhere directly (the agency commission could add anything upwards, from >£1300 a month), therefore you would as the BSM be adding their overhead to your invoice, for a mere introduction, yet on an indefinite basis (so would need to agree a fixed fee, otherwise added overtime/variations extra could/would be a real pain etc.), and you would end up paying them as the client would only want to pay one invoice, not two for the same services (one for the actual work, and another for emailing your CV inc. paying circa £170 to "Totaljobs" for advertising) - makes sense!. 

If a services manager really wants to call themselves self-employed and/or a business, they should be able to demonstrate a costing-model for their services/business, based on something like above (resource planner), professional team consultants have been doing this for decades, based on RIBA stages for their design input, and payment application milestones, so it is nothing new, it just/only means becoming commercially astute for most people, opposed to just filling in time sheets. often for just attending work with no profit/loss risk as so ever.

"The main difference will be, you will cost more at the start, and at the end/closing-out phases of the project (precon, and commissioning/handover periods) if done correctly and displayed clearly in above the resource planner example, whereby consultants will cost more at the start, during their design completion (contract dependant on if "full" design), and then phase-out during design completion, into what becomes a watching brief post design completion - some will supervise the commissioning phase that’s dependant on the clients route regarding an independent commissioning manager or subcontractor specialist doing just witness attendances - but you get the idea".

Ketley was pricing entire building in his 20's, and he loved it (but was always good with maths and an eye for detail) - he struggles to understand why building a bill of quantities, add fitting fit times and OH&P is difficult for people who call themselves self-employed...

On another matter away from prelim resource costing:

Also ask yourself how you can calculate labour numbers vs. program, it is very easy but can the/you as the BSM look at a floor space, and say I need "X" amount of weeks with "X" amount of men, and/or the usual opposite approach, you have "X" amount of weeks to finish 1st fix, how does one calculate how many men they need ? a clue would be a quantified cheque of rate c/w fit-times, or you do a take-off and use a rates/measurement book such as the NSR...

Over and over we argue why our staff numbers go up and down often due to cash-flow with sub-sub’s, and availability of labour, but at the very least we should know the overall fit time in hours needed to complete the task if working to tight deadlines, otherwise we end up doing weekends, nights and longer days etc and end up asking ourselves did we start off correctly, or do we blame the poor old planner as an easy target again – standards need attention with BSM’s hence why IBSM was created...

One of the core issues being subcontractors will sub-sub the trades out to others again, with time allocation missing due to making time harder to calculate contractually by all-in sums, which are better profit-wise down the line, but also under D&B if no one will pay for more materials installed than allowed for in the sub-sub's SOR, there is an argument that it is at their be a risk to them under the "lump-sum fixed price", thereby asking for quantified SOR ahead of placing an order raises the question are they being used purely to cost the job for others, “KK” has argued/debated many time during tender processes that he has fully quantified schedule of rates for the M&E, but will review with client team post contract award, purely because he has heard the competition were already celebrating the win but were/may of been more expensive hence the client team wanting KK's quantities to measure against their preferred contractor therefore “yes” used for costing purposes, to enable them to drive a discount from the preferred by a remeasure or alike exercise…

Forgetting the hard work and cost it takes to tender projects, if you are open-book and/or on a measured works contract things differ then, but when it’s a lump-sum D&B things become political at times, even to a point where a company will place a rogue sum so cheap it needs review/ consideration, but only because they know they are being used for costing, and have placed alot of clarification/exclusions in addition, and/or vice-versa a company may put an elevated price in because they do not want to say no, have not the time to do the take-off properly, but at the same time it may be a horrible/risky project they do not want/need at that time, and/or they may have resource issues at that time, but would do it at the higher price by one way or another,  therefore if you have a mix of both the BSM and QS will need to knuckle down and know how to fix the issue through a draining adding/omitting/plugging review but again if all tenderers have been given a pricing schedule this is much easier if not, and their returns are not uniform with one another, the levelling will be much more difficult resulting in constant email ping-pong to answer each and every observation - the lesson is - do it right and it flows well, cut corners and reap the consequences... 

Tip – If the commercial team are sending out or have sent out the enquiries remind them you will not have the time to deal with messy returns and they should have asked the Snr. BSM to create a CSA if one was not part of the tender return, also if the client has a tender return CSA, then request/respond to all tenderers that under each client header you want the build-up for item example a client may use a simplified CAWS style schedule such as “Y51 Testing & Commissioning” or nowadays with the revised numbered NRM (new rules of measure) by RICS but then we have to provide COBie codes for use in BIM in line with revised uniclass coding,

"If you are an IBSM (1%er) you will find this easy anoth, if not but you are happy just doing your part on attendance money - there is nothing wrong with that at all, not all need to be IBSM Cradle-to-Gravers" - "Enjoy your work-life balance, don't struggle trying to learn things that you may not even need to know in your position"... (Ketley)