Most homes in the UK have a single clear construction type, such as brick, stone or timber frame, and do not require any calculations. However, non-standard homes, renovated properties and buildings that combine several materials often need a percentage split.
This guide explains when you can enter 100 percent for a single material, when you need to break it down, and how to calculate the percentages easily.
This question often causes confusion, but in most cases it can be answered quickly once you know which category your home falls into.
Quick guide
In most cases after answering “No”:
👉 If your home uses one non-standard construction type throughout, select it and enter 100 percent.
You only need to enter percentages if:
👉 Your home combines two or more different exterior wall construction types.
When you can simply select one construction type
Even if you have answered “No”, many homes still use a single non-standard construction type. In these cases, you can select the appropriate option and enter 100 percent.
Many homes, even if not traditionally built, fall into a single construction category. If your home is entirely one material listed in the quote options, you can enter 100 percent without any further calculation.
Examples include:
- Timber Frame/Brick
- Timber/Plaster
- Steel Frame/Brick
- Steel Frame/Render or Pebbledash
- Steel Frame/Wood Shiplap
If the whole property has been constructed using one method, select that option and enter 100 percent. This is the simplest and most common scenario.
The same applies to prefabricated buildings. If the entire structure consists of:
- Prefabricated Building – Combustible Materials
- Prefabricated Building – Non-Combustible Materials
you can safely enter 100 percent.
When you need to enter percentages
You only need to calculate percentages if the property uses more than one construction type. This is typical in the following situations.
1. Mixed-material homes
Some properties combine two or more major construction methods. Common combinations include:
- Timber frame with cob
- Stone with timber, (common in barn conversions)
- Flint with brick
- SIP panels with other materials
- Steel frame with glass sections
2. Homes with extensions or later additions
Homes with extensions or later additions often use different construction types for each part of the building. An older masonry house may have a newer timber frame extension, or vice versa. Each distinct section may use a different structural material.
3. Modern or specialist construction systems
Properties built with alternative materials may combine:
- Structurally Insulated Panels (SIPs)
- Reinforced PVC
- Glass
- Metal
- Fibreglass
- Steel frame elements
4. Historic or regional construction types
Traditional methods such as:
- Cob
- Wattle and daub
- Stramit
- Clunch
- Flint
- Stone with timber elements
These materials often appear in older or heritage homes, including many listed buildings. A percentage breakdown helps insurers understand how much of the property is built from each type. Further guidance on traditional construction can be found at Historic England.
What counts as the construction material
Construction percentages refer to the load bearing exterior walls, not internal features.
Do not include:
- Interior stud walls
- Timber floors or roof timbers
- Decorative beams
- Cosmetic cladding
- Porches or conservatories unless integrated into the structural envelope
- Partition walls or loft framing
👉 Only the materials that make up the external load bearing structure should be counted.
A simple way to calculate the construction percentages
You do not need exact measurements. Insurers expect a reasonable and honest estimate based on the information available. The following method works for most non-standard properties.
Step 1: Break the home into sections
Consider the main house, extensions, attached garages and significant structural additions.
Step 2: Identify the construction type of each section
Check survey documents, EPC notes or planning records if you are unsure. Guidance on common construction materials can also be found on the Planning Portal.
Step 3: Estimate the proportion of each construction method
Think about the footprint and layout of your home and estimate what percentage each part contributes to the overall structure.
Step 4: Ensure the total reaches 100 percent
Your figures must add up to 100 percent to proceed with the quote.
Clear examples
Below are examples based on scenarios customers commonly encounter.
Example 1: Timber frame and cob construction
A farmhouse extended in two stages, with the original part built in cob and the later addition built with a timber frame.
Timber Frame = 40 percent
Cob Construction = 60 percent
Total = 100 percent
Example 2: Steel frame, glass and structurally insulated panels
A modern architect designed property where large areas of structural glazing form part of the exterior wall construction, alongside other materials.
Steel Frame = 40 percent
Glass = 35 percent
Structurally Insulated Panels = 25 percent
Total = 100 percent
Example 3: Brick main house with a timber extension
Common in renovated homes.
Brick = 80 percent
Timber Frame/Brick = 20 percent
Total = 100 percent
Example 4: Stone cottage with later timber and flint additions
A typical mixed-material rural property.
Stone = 60 percent
Timber Frame/Brick = 20 percent
Flint = 20 percent
Total = 100 percent
How to confirm your construction type
If you are unsure, the following sources usually provide reliable information:
- EPC report
- HomeBuyer Report or Building Survey
- Original planning or building control documents
- Developer or builder information for newer homes
- Structural drawings if the home was self-built or altered extensively
Professional confirmation can be helpful if the property is unusual or historic, or if documentation is unclear.
Conclusion
Calculating construction percentages is straightforward once you understand what counts as the structural exterior wall material.
Many homes only require a single construction type to be entered at 100 percent, particularly where the property is built entirely using one method.
Percentages are only required when a building uses a mixture of materials, such as cob and timber, steel and glass, or modern composite systems.
By breaking your home into sections, estimating their contribution to the overall structure and ensuring the total reaches 100 percent, you can complete your insurance quote with confidence.
Accurate information helps your insurer understand the true nature of the property and ensures your cover is set up correctly.
If you would like more information on how different construction types are classified, visit our non-standard home insurance page.
