What a Main Contractor Is Responsible For
The main contractor is the business your contract for the work is with. Here is what that makes them responsible for, and what stays with you.
Who answers for the work
The main contractor is the business you contract with to carry out the work. That makes them answerable to you for the whole job, including the parts other people do.
On a small job, the main contractor may be one person doing everything. On a larger one, they may bring in specialists for particular parts and run the site as a whole. Either way, the main contractor is the one your contract is with, and so the one responsible to you for the work.
Knowing what that covers helps you ask the right questions before you sign, understand who to talk to when something needs sorting, and spot the few responsibilities that stay with you as the owner.
This guide explains the main contractor's role on a typical domestic project. It sits within our guide to choosing and checking a building contractor. It is general information, not legal advice.
The term
What "main contractor" means
"Main contractor" describes a position in the arrangement rather than a type of business. It is the firm that contracts with you, the client, to deliver the work. Any other firms it brings in, such as an electrician, a plasterer or a scaffolding company, work for the main contractor, not for you.
The main contractor is also distinct from other people who may be involved in a project. An architect or designer produces the design. Building control, whether the council or a private building control body, checks compliance with Building Regulations. A project manager or coordinator may organise parts of the process. None of them is the main contractor unless they have also agreed to carry out the work.
Our short answer on what a main contractor is covers the definition. This page goes into what the role involves.
The role
What the main contractor is usually responsible for
The details depend on what you agree, so the quotation and any contract matter. These are the responsibilities that normally sit with the main contractor.
Carrying out the work as agreed
Delivering the scope set out in the quotation or contract, to a proper standard, using the materials agreed.
Everyone they bring on site
Their own staff and any other firms they engage. If part of the work is done by someone they brought in, the main contractor remains answerable to you for it.
Running the site safely
Planning the work so it is done safely, for the people doing it, for you and your household, and for neighbours and passers-by.
Materials and deliveries
Ordering, receiving and storing what is needed, where materials are included in the price, as they usually are.
Their own insurance
Holding the insurance appropriate to their business and the work, such as public liability cover. Our guide to checking a builder's insurance explains what to ask for.
Putting their own defects right
Returning to fix problems with their workmanship, under the terms of any warranty they give and under your wider rights as a consumer.
The standard of the work
Reasonable care and skill
When a trader provides a service to a consumer, the Consumer Rights Act 2015 says the service must be carried out with reasonable care and skill. What the trader tells you about the service, and relies on to win the work, can also form part of the contract. Where no price or timescale has been agreed, the law expects a reasonable price and a reasonable time.
In practical terms, the main contractor is responsible for the work being done competently and as agreed. If it isn't, your rights under the Act are against the business you contracted with, which is the main contractor. Citizens Advice has clear guidance on what those rights are and how to use them.
This is also why the quotation matters so much. The clearer the written scope, materials and standards, the easier it is for both of you to know whether the job has been done as agreed. This is general information, not legal advice.
Other firms on the job
When the main contractor brings in specialists
It is common, and often sensible, for a main contractor to bring in specialists for parts of a job. A builder running an extension might use a separate electrician, plumber or plasterer. Those firms are usually called subcontractors, and their agreement is with the main contractor rather than with you.
For you, the main point is simple: your contract is with the main contractor, so they are answerable to you for the whole job, including the work their subcontractors do. If something a specialist did needs putting right, you raise it with the main contractor, and it is for them to deal with the firm they brought in.
It is still worth asking at the start which parts of the job will be done by other firms and whether those firms hold any registrations the work requires. Our answer on who is responsible for a builder's subcontractors covers the detail.
Health and safety
Safety on a domestic project
The Construction (Design and Management) Regulations 2015, usually called CDM, apply to building work in homes as well as on commercial sites. They set out duties for clients, designers and contractors.
For domestic clients, the regulations are written so that you are not expected to take on the client's duties yourself. Where there is only one contractor, those duties normally pass to that contractor. Where there is more than one contractor, they normally pass to the principal contractor. A designer can take them on instead if that is agreed in writing.
In practice, this means the main contractor on a typical domestic job is responsible for planning the work safely, managing the site and making sure the people working on it know what they are doing. The Health and Safety Executive publishes plain guidance on CDM for domestic clients. This is general information, not legal advice.
Who does what
Usually the contractor's, usually yours
A general picture for a typical home project. What you agree in writing can change it, so check your quotation and any contract.
Usually the main contractor's
- Carrying out the agreed work competently
- Managing their team and any specialists they bring in
- Running the site safely
- Protecting your property during the work, as agreed
- Removing waste, where included
- Holding their own insurance
- Putting right defects in their workmanship
Usually yours as the owner
- Deciding what you want done and approving changes
- Planning permission, where it is needed
- Party wall notices, where the work affects a shared wall or boundary
- Giving access to the areas the work needs
- Paying as agreed in the quotation
- Raising problems promptly and in writing
- Agreeing in writing who deals with building control
Planning permission and party wall matters are generally the owner's responsibility, even though many contractors will help. Building Regulations approval is often arranged by the contractor, but responsibility is shared and the owner can be affected if work does not comply, so agree in writing who applies and who will give you the certificate at the end. The Planning Portal and GOV.UK explain each in plain terms. This is general information, not legal advice.
Before you start
Get the responsibilities in writing
Most disagreements about responsibility come from something that was assumed rather than written down. A few lines on the quotation or in an exchange of emails prevent most of them.
Confirm who the main contractor is
The business name on the quotation should be the business that will carry out the work and that you pay.
Agree the scope in detail
What is included and what is not, including scaffolding, waste, making good and clearing up at the end.
Agree who handles permissions
Building control, and any other approvals, with the name of whoever will deal with each.
Record the warranty
How long the workmanship warranty lasts, when it starts and what it covers.
Name the contact
Who you speak to during the job, and how. Our answer on what paperwork to get before work starts lists the rest.
Where the role ends
What a main contractor doesn't usually do
Unless you have agreed otherwise, a main contractor is not usually your designer. On a design-and-build arrangement they may be, but where you have an architect or designer, the design is their responsibility and the contractor builds to it.
A main contractor is not building control either. Building control checks that the work complies with Building Regulations. That is not the same as checking the quality of the finish, and a completion certificate is not a warranty.
Nor is the main contractor necessarily the person who organises everything around the job. Some contractors handle all of it; others would rather concentrate on the work. Where someone else coordinates the process, it helps to be clear which parts sit with whom. Our answer on what a project coordinator does explains how that role fits alongside the contractor's, and questions to ask at a site visit helps you pin it down early.
When we coordinate the work
Your contractor is named as the main contractor
When Mortaro coordinates a project, your quotation names the independent contractor from our network as your appointed main contractor. They carry out the work, hold the insurance and give the workmanship warranty, which is a minimum of 12 months across our network and usually runs from completion. Your construction contract is with them.
Mortaro coordinates the process around the work: the site visit, the quotation, communication, start dates and payment administration. If something needs putting right, we raise it with your contractor and push for a resolution. Who you're dealing with sets out the arrangement, and putting things right explains what we do if there is a problem.
Straight answers
Questions about main contractors
Is the main contractor responsible for their subcontractors' work?
Generally, yes. Your contract is with the main contractor, so they are answerable to you for the whole job, including parts done by firms they bring in. You would normally raise any problem with the main contractor.
Who is responsible for getting building control sign-off?
It depends on what is agreed. Contractors often arrange it, or self-certify through a competent person scheme, but the owner can be affected if work doesn't comply. Agree in writing who will deal with it and ask for the certificate at the end.
Who is responsible for planning permission?
Generally the owner. A contractor or designer may help you apply, but it is your property and your application. Check with your local planning authority or the Planning Portal if you are unsure whether it is needed.
Is the main contractor responsible for damage to my property?
If the contractor causes damage while carrying out the work, you would normally raise it with them, and this is one reason public liability insurance matters. Report any damage promptly, in writing, with photographs.
Does a main contractor have to be a limited company?
No. Many main contractors on domestic jobs are sole traders or partnerships, and that is perfectly normal. What matters more is that you know exactly which business you are contracting with and that its details appear on the quotation. Our guide to sole trader vs limited company explains the practical differences.
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