Head of Content
Head of Bridging and Commercial
Affordability and repayment calculations for self-build mortgages can be complex, but we can help you make sense of them. In this guide, you will find a self-build mortgage calculator for working out the rolling cost of your project, and information about how affordability is calculated for this type of mortgage.
Calculate the cost of your self-build mortgage
You can use our specially designed calculator below to work out how much your self-build mortgage will cost you each month, at various stages of the project.
Set the number of tranches your project will involve, input the amount you will need for each one along with an interest rate, and our calculator will do the rest.
Total Amount Borrowed: £0.00
Monthly Repayments: £0.00
How does this calculator work?
Self-build mortgage funds are delivered in staged tranches and you will only be charged interest on the capital you have drawn down. This calculator takes this into account by allowing you to define each tranche and input the amount you will be borrowing for it.
The tranches you can select are:
- Land purchase
- Substructure
- Wallplate/eaves height
- Roof tiling
- First fix
- Additional fix
- Final payment
- Other (use for any that don’t fit the above categories)
This calculator takes the amounts entered for each tranche and works out the total monthly interest payments for them all combined to tally up the costs.
When it can be useful
All self-build mortgage calculators have their limitations as these mortgages can be complex, which is why we would recommend speaking to one of our specialist self-build mortgage brokers for bespoke calculations after you have run some rough ones yourself.
But our self-build mortgage calculator is a good starting point for that initial number crunching. This tool is useful for self-builders who have planned ahead and worked out how much capital they are likely to need for each stage of the project and defined each one.
It is also useful to get an idea of the rolling cost of the project as the lender distributes each staged payment. You could keep revisiting this page as your build enters a new tranche to input the latest round of funding and find out how much your monthly payments will change.
Speak to a self-build mortgage specialist today
How affordability is calculated for self-build mortgages
You won’t find any calculators online that can work out the affordability of a self-build mortgage definitively. This is because there are so many factors to take on board when working out how much capital you need to build a property from scratch.
As a general rule, however, the maximum you can borrow on a self-build mortgage is typically 75-85% of the approximate value of the property upon completion.
Some lenders have borrowing caps to be mindful of too, and they tend to range between £500,000 and £4 million, so you will need a specialist lender to borrow more than that.
To get a true picture of the amount you need to borrow, factor in the following variables:
- Whether you will be self-managing the project or using a contractor
- The size of building plot required
- The size of the property you’re building
- The type of building materials needed
- Internal decoration and design costs
- External landscaping costs
What your repayments will be when you remortgage
Once you have completed the building work, you will need to remortgage onto a standard residential agreement, based on the post-completion value of the property.
If you have an idea of what the post-completion value will be, you can use our mortgage repayment calculator below to work out what your monthly payments will look like:
Speak to a self-build mortgage specialist today
Speaking to a mortgage broker is highly recommended if you are applying for a self-build mortgage. While online calculators can be a good starting point, it is recommended that you consult with one of our experts for bespoke calculations before you get started.
Not only can they provide you with these, they will also go through all of your options with you and help you find the ideal lender, rate and deal for your self-build mortgage.
Here are just some of the reasons self-builders choose us for their mortgage needs:
- Our brokers are experts on self-build mortgages
- They can access exclusive deals you won’t find elsewhere
- We are 5-star rated on leading review websites
- They can help you with your remortgage upon completion
Ready to get started with your self-build mortgage plans and take advantage of a free, no-obligation chat with a broker who specialises in this area? Get started here.
FAQs
No. Our self-build mortgage calculator will work just fine for projects outside of England and Wales, specifically ones situated in Scotland or Northern Ireland.
Self-build mortgages are available in these territories and the way the repayments on them are calculated is no different to in any other parts of the United Kingdom.
Choosing an Adviser
Selecting a qualified and experienced mortgage adviser is of great importance. To choose a suitable adviser, evaluate their qualifications, experience, and reputation, and ensure they are regulated by the Financial Conduct Authority (FCA).
Read reviews from previous clients and make sure they provide a clear explanation of the products and services they offer, as well as the fees and charges associated with them.