Quote vs estimate: What's the difference when pricing up your build?

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Weighing up quote vs estimate when it comes to getting an idea of how much your project is going to cost you?

Finding a builder who you trust to deliver you the results you want when it comes to your self build, renovation or extension should be top of your priority list when starting out and while you won't want to pay over the odds, is is also important to be aware that cheapest isn't always best.

The terms ‘quote’ and ‘estimate’ can easily be mistaken for the same thing. However, their meanings are actually very different and proceeding on the basis of one or the other will almost certainly be met with very different outcomes.

Quote vs estimate: What is a quote?

If you are asking how much does it cost to build a house or extend, a quote should provide you with a fixed final cost for your project. It should be in writing and set out all the detailed requirements in full, with pricing ideally broken down against each element. Some quotes will include a timeline. 

Quotes are mostly stated to be valid for a specified time, as your builder/tradesperson will be bound by the price quoted and material and labour prices are subject to change. For a quote to be binding, it must be accepted within the specified timescale, otherwise the quote will need to be renewed.

What is an estimate comprised of?

An estimate is a rough approximation of what the total project might cost. It should be in writing and will usually include a disclaimer to make clear the final cost is subject to change once more details are known. 

An estimate will typically include just a high level statement of requirements. The cost will be an estimation based on the builder or tradesperson’s experience of similar work undertaken. Experienced builders and tradespeople should generally be expected to estimate within, say, 10% to 20% of the final cost, but as the pricing is not done in detail, the potential for unforeseen elements to arise increases, which may further impact the final cost.

What is the difference between a quote and an estimate?

If you are provided with a quote, you should expect to pay exactly that sum for the finished project. 

An estimate is a more general assessment of what the end cost might be. It is rare for an estimate to match the final cost of a job as the initial pricing will not have been detailed enough. 

A quote is considered binding (subject to the issues we’ll look at below) whereas estimates are not. Estimates are very useful at the outset of a project to get rough figures to establish if it’s financially viable. However, you should always aim to secure final quotes prior to proceeding with building work.  

What are 'provisional sums' and 'price cost sums'?

Both quotes and estimates can include references to ‘provisional sums’ and ‘prime cost’ sums. These terms are used where elements of a project are not yet finalised but a cost needs to be allocated to compile the quote or estimate.  

Provisional sums are used where general areas of a project have not yet been fully designed. For example, an extension project may not have a kitchen design completed, but you know whether it will be in the region of say £10k or £35k and this figure will be inserted. The provisional sum will not be a binding cost if used in a quote and will be replaced with the actual cost when known.  

Prime costs sums (PC sums) are used where a specific item has been identified for pricing but the specification has not yet been decided. For example, a quote may include a PC sum for tiling, but the actual tiles have not yet been chosen. Again, the final cost will include the actual price of the tiles. 

Provisional sums and PC sums are often necessary in compiling both quotes and estimates, as very few projects (unless at the smallest end of the scale) are capable of being specified to the very last detail. 

They are useful tools in enabling a quote or estimate to be compiled. Where used in a quote, they enable the guaranteed costs to be identified and help identify costs which are yet to be fixed. 

It goes without saying that the lower the amount of provisional and PC sums, the closer you will get to a guaranteed final cost, so if budgets are tight, it is well worth investing the time and energy in nailing down all of the variables in your project.

When will an estimate be given instead of a quote?

If you provide insufficient detail to a builder/tradesperson, they will be unable to accurately price the works and therefore commit themselves to a final fixed quote, so an estimate is the only option. Alternatively, you may provide full details of the works, but the project may be of a type where unknown issues are more likely to arise.

Renovations are a good example of this, particularly with older buildings, as sometimes you simply can’t tell what you are going to find until you actually open up a wall, ceiling or floor. 

It may also be the case that the builder/tradesperson simply doesn’t have the time to spend on establishing the finer details and obtaining quotes for materials in order to provide a quote. They have no guarantee they will be selected for the work, so if they are already busy, an estimate may be the best they can offer.   

Is a quote better than an estimate?

A quote should give you the greatest cost certainty for your project. It means the builder/tradesperson you have engaged has taken a thorough look at the requirements and broken down all the costs involved. When the works are completed, you should pay the amount stated in the quote.  A quote will be equally beneficial for the person undertaking the project as they will have taken the time to accurately assess the work required and the costs involved and won’t be running the risk of under-pricing the job, which can lead to all kinds of issues.

The key to achieving a quote is the level of detail you are able to provide. This includes any plans/drawings, specification of works and finalising as many of the design and finishing details as possible for your build.

If you are contemplating an extension, loft conversion or any major building works, it’s a good idea to engage a QS (quantity surveyor) to produce a BQ (bill of quantities) to enable your builders and tradespeople to provide you with quotes against a detailed single specification. 

What factors might change a quote?

The total presented on a quote is the final amount you’ll pay at the end of the job. However, there are factors that can change this, for example, if during the works you decide to alter some of the items which were originally priced. Your builder/tradesperson cannot be held to their quote if you have changed the scope. 

The best approach would be to discuss your new requirements as early as possible and seek a new quote for the additional work. Failing to do this can lead to disputes and unexpected costs at the end of the works. 

Even if you do not change the specification at all, your builder may encounter issues which mean unforeseen work will need to be added to the quote. This can be problematic if disputes arise as to what was reasonably foreseeable by an experienced builder/tradesperson and should have been included at the outset

How can you avoid issues?

It’s essential to make yourself available to your builder/tradesperson so that any issues can be dealt with quickly should they arise. Try to meet regularly to review costs as the project progresses. If your builder encounters unforeseen issues which will impact cost and you are aware of it early on, then you’ll have the opportunity to adjust the remaining works to keep the overall project within budget.    

Discussing cost issues can be uncomfortable for all parties, so try to develop an open relationship with your builder/tradesperson to encourage early warnings if things are not going as expected.

tim phillips
Tim Phillips

Tim Phillips is a quantity surveyor with almost 30 years of experience across the commercial and residential construction sector.


Tim Phillips is an experienced senior quantity surveyor and estimator and has worked in the construction industry for over 35 years. He has worked on many varied projects in this time, for corporates, public bodies and private residential clients, managing multi-million budgets. 


For the past 13 years, Tim has worked on a freelance basis, whilst managing his rental property portfolio. He has extensive experience of undertaking his own full-scale house renovations. He is also a speaker and expert at the Homebuilding & Renovating Shows.