In this guide
If you’re an architect involved in designing or overseeing basements - even occasionally - the short answer is yes, you almost certainly need your Professional Indemnity (PI) insurance to include basement works.
Why Basements Matter So Much
Basement projects carry a disproportionately high risk compared to above-ground work. Here’s why insurers care - and why you should too:
- Ground movement / subsidence: Digging into the ground can destabilise neighbouring properties.
- Water ingress: Incorrect waterproofing design leads to damp, mould, and expensive claims.
- Structural failures: Mistakes in retaining wall design, underpinning, or piling can be catastrophic.
- Neighbour disputes: Basements often trigger boundary and party wall issues - and architects often get pulled into these by default.
What Happens If It's Not Included?
Many PI policies exclude basement works by default - or impose depth restrictions (e.g. no deeper than 1 metre, or no new basements at all).
If you carry out basement work and it’s not covered:
- Any claim - even if you’re not at fault - could be rejected outright
- You’ll be personally liable for the defence costs
- Your client could pursue you directly for rectification and loss of use
Even working on existing basement refurbishments (without new structural work) can fall into a grey area. It only takes one damp patch and an unhappy client for it to escalate.
How to Check Your Policy
Look for wording like:
- “Basement works excluded”
- “Work involving excavation deeper than X metres is excluded”
- “Cover excludes structural design or oversight of sub-ground construction”
If any of those apply, and you’re involved in basement design, your policy needs amending.
When You Definitely Need It
You should ensure basement cover is included if:
- You design new basements, cellars or below-ground levels
- You provide oversight or sign off on other parties’ basement designs
- You deal with basement conversions that impact structure, damp proofing, or services
- Your projects involve underpinning, piling, or significant excavation
Even if you're not the structural engineer, if your name is on the design team or you’re providing contract administration, you’re a target in any claim.
What It Typically Costs
Premium increases for including basement work vary depending on:
- Depth and complexity
- % of your annual work that involves basements
- Whether you use external engineers
In some cases, it can be a small loading. In others, insurers may require additional endorsements or apply higher excesses. But that’s still better than facing a 6-figure claim uncovered.
Get Advice From A Specialist
If you ever touch basement projects, and your PI policy excludes them - your business is exposed. It's one of the most common blind spots for smaller firms and sole traders.
A conversation with a broker who understands architectural PI insurance is essential. Don’t assume you’re covered. Click the button above to submit your details and discuss with an experienced broker.
Frequently asked questions
Do architects need basement works covered on their PI insurance?
Yes. If you design or oversee basements, even occasionally, your professional indemnity policy almost certainly needs to include basement works.
Why do PI insurers treat basement work as high risk?
Basements carry a disproportionately high risk because of ground movement and subsidence affecting neighbours, water ingress from poor waterproofing design, structural failures in retaining walls, underpinning or piling, and party wall disputes that often draw in the architect.
Are basement works excluded from standard PI policies?
Many PI policies exclude basement works by default or impose depth restrictions, such as nothing deeper than 1 metre or no new basements at all.
What happens if I do basement work and my PI policy excludes it?
Any claim could be rejected outright even if you are not at fault, you would be personally liable for defence costs, and the client could pursue you directly for rectification and loss of use.
How do I check whether my PI policy covers basements?
Look for wording such as 'basement works excluded', exclusions for excavation deeper than a stated depth, or exclusions for structural design or oversight of sub-ground construction. If any apply and you work on basements, the policy needs amending.
How much more does it cost to add basement cover to PI insurance?
It varies with depth and complexity, the share of your work involving basements and whether you use external engineers. Sometimes it is a small loading; in other cases insurers require additional endorsements or higher excesses.
Michael Foote, Insurance & Finance Expert
Michael Foote is the founder of Quote Goat and has over 20 years experience working in finance & insurance. Since launching Quote Goat he has appeared on TV as well as many of the largest online publications including Forbes, The Telegraph and The Metro. Prior to Quote Goat, he worked in finance in the city.
