How to Measure a Hearth
Whether you're replacing an old fireplace hearth or ordering a brand-new bespoke slate or granite hearth, getting the measurements right is the most important part of the process.
At Mrs Stone Store, we manufacture custom-cut hearths to your exact dimensions, so taking accurate measurements ensures your new hearth fits perfectly first time. Fortunately, measuring a hearth is much easier than many people think.
In this guide we'll explain exactly what you'll need, how to measure different hearth shapes, and the common mistakes to avoid.
Why Accurate Hearth Measurements Matter
Unlike carpet or timber flooring, natural stone can't simply be trimmed once it arrives.
A hearth that's even a few millimetres too large may not fit between your walls or fireplace opening, while one that's too small can leave unsightly gaps.
Taking accurate measurements means:
- A perfect fit
- Faster installation
- No expensive alterations
- Better overall appearance
- Greater safety around your stove or fireplace
If you're unsure at any stage, our team is always happy to check your measurements before your hearth is cut.
What You'll Need
Before you begin, gather the following:
- Steel tape measure
- Pencil
- Paper
- Spirit level (recommended)
- Straight edge or long piece of timber (useful if walls aren't straight)
It also helps to have another person hold the tape measure for longer measurements.
Before You Measure
Before taking any measurements, decide:
- Will your hearth sit against skirting boards?
- Are the skirting boards staying or being removed?
- Is your fireplace perfectly square?
- Will the hearth be flush with the floor or raised?
These small details make a big difference when ordering a bespoke hearth.
Measuring a Standard Rectangular Hearth
A rectangular hearth is the simplest design to measure.
Step 1 – Measure the Width
Measure from one side of the intended hearth to the other.
Take the measurement along the wall rather than across the front edge.
Measure twice to confirm.
Step 2 – Measure the Depth
Measure from the wall to the front edge of where you'd like the hearth to finish.
Take this measurement on both the left and right-hand sides.
If they differ, use the smaller measurement or contact us for advice.
Step 3 – Check for Square
Very few fireplaces are perfectly square.
Measure the depth in several places.
If one side is deeper than the other by more than a few millimetres, let us know when ordering.
Our cutting team can often manufacture the hearth to suit.
Measuring a T-Shaped Hearth
T-shaped hearths are one of our most popular bespoke options.
These fit inside the fireplace opening while extending into the room.
Measure:
Overall Width
Measure the full width across the front.
Front Projection
Measure from the fireplace opening to where you'd like the hearth to finish.
Fireplace Opening Width
Measure the internal width of the fireplace recess.
Take measurements at:
- Front
- Middle
- Back
Use the smallest measurement.
Fireplace Recess Depth
Measure from the front of the fireplace opening to the back wall.
Again, measure both sides.
Fireplaces are rarely perfectly symmetrical. Taking several measurements helps ensure the hearth fits correctly.
Don't Forget Expansion Gaps
Natural stone expands slightly as it warms up.
For this reason, it's good practice to allow a small expansion gap between the hearth and surrounding walls.
A gap of around 5mm on each side is generally recommended and can later be filled with a colour-matched flexible sealant if required.
Measuring Around Skirting Boards
This is one of the most common mistakes customers make.
If your skirting boards will be removed before installation:
Measure to the wall, not to the skirting.
If the skirting is staying:
Measure the visible space between them.
Always measure the finished installation area—not the room as it looks today.
Measure Twice
Professional stonemasons have an old saying:
Measure twice, cut once.
Before placing your order:
- Check every measurement again.
- Make sure you haven't mixed up width and depth.
- Confirm all measurements are in millimetres.
- Draw a simple sketch showing every dimension.
A quick sketch can prevent costly mistakes and helps our production team verify your order.
Should You Measure the Existing Hearth?
If you're replacing an existing hearth and you're happy with its size, measuring the old hearth is often the easiest option.
However, also check:
- Has the floor changed?
- Has new flooring been installed?
- Are you changing the fireplace surround?
- Will a new stove require different clearances?
Small alterations can affect the ideal hearth size.
Hearth Regulations
If you're installing a new wood-burning stove or open fire, your hearth must comply with current UK Building Regulations.
The required size depends on:
- The appliance
- Installation method
- Distance to combustible materials
- Manufacturer's instructions
If you're unsure, always consult your installer before ordering. Current guidance also recommends considering hearth projection, stove door swing and required clearances.
Sending Your Measurements to Mrs Stone Store
Once you've taken your measurements, simply send us:
- A sketch with dimensions
- Photos of your fireplace
- Any additional notes
Our experienced team will review everything before production begins and contact you if anything looks unusual.
We manufacture bespoke:
- Slate hearths
- Granite hearths
- Limestone hearths
- Sandstone hearths
- T-shaped hearths
- Teardrop hearths
- Corner hearths
- Boxed and lipped hearths
- Cut-to-size hearths
Every hearth is precision cut in our workshop and finished to the highest standard.
Need Help Measuring Your Hearth?
At Mrs Stone Store, we understand that every fireplace is different. Whether you're renovating a period property, installing a modern wood burner or replacing an existing hearth, we're here to help.
If you're unsure about any measurement, simply send us a few photographs along with your approximate dimensions. Our experienced team can often identify potential issues before your hearth is manufactured, helping you achieve the perfect fit first time.
When you order from Mrs Stone Store, you're not just buying a hearth—you're benefiting from expert advice, precision stone cutting and years of experience supplying bespoke hearths throughout the UK.