What’s the Difference Between a Principal Contractor and a Subcontractor in Estimating?
In simple words, the Principal Contractor is responsible for everything on the job, from start to finish. On the other hand, a Subcontractor is only responsible for the specific part of the job they are doing — and that’s it.
🧾 Responsibilities in Estimating
🏗 Principal Contractor
When you’re estimating as the Principal Contractor, you are expected to:
Cover the entire job scope
Include all project-related costs and responsibilities, even if they’re not construction-specific
Be the first to arrive on site and last to leave
Take responsibility for site-wide risks, permits, approvals, and coordination
You cannot make exclusions like:
“Traffic control to be provided by others”
“Council fees to be paid by others”
There is no ‘others’ — everything is on your head. You must allow for:
Traffic control
Council and authority fees
Site establishment and amenities
Environmental controls
Safety documentation
Reinstatements
Surveyors
Dealing with contaminated or unsuitable ground material
All approvals, cleanup, and reporting
The Principal Contractor holds more risk, but if managed well, it also comes with greater opportunity for profit — especially when scope is clearly defined for each subcontractor and supplier.
🔧 Subcontractor
A Subcontractor is only responsible for their own trade scope and is generally allowed to make exclusions such as:
“Traffic control to be provided by Principal Contractor”
“Council fees to be paid by others”
“Surveyor to be engaged by Principal Contractor”
“Permanent reinstatement by others”
“Contaminated material to be handled by Principal Contractor”
Subcontractors are not expected to manage the overall job — only their portion. In estimation, this means they often exclude broader site costs and risks, passing those on to the Principal Contractor.
💡 Key Point for Estimators
If you’re pricing the same job, but once as a Subcontractor and once as a Principal Contractor, the estimate will look very different.
When estimating as a Principal Contractor:
You need to include all project components
Be mindful of every requirement, even indirect ones
Clearly define what each party is responsible for
Make sure all allowances and qualifications are made in your submission
Failing to do this can result in underpricing, taking on unintended risks, or losing profitability on the job.
📞 Want help pricing accurately based on your contract role?
WSE Sydney specializes in detailed, role-specific estimating.
📧 tenders@watersewerestimatingsydney.com.au
📱 +61 451 404 645