Layered PI Programmes — Design Firms
PI insurance layered programmes for architects and engineers — UK 2026
A layered professional indemnity programme is a structural way of buying higher aggregate cover than any single insurer will comfortably write on one paper. This page explains how design-firm layered towers work, what to look for at each interface, and where the model tends to make sense in practice.
What ‘layered’ means in professional indemnity
A single-insurer programme is one contract for the full limit — for example £5m any one claim and in the aggregate, all written by one insurer on one wording. A layered programme is several contracts stacked vertically. The primary layer sits at the bottom and pays first-loss claims from ground up. Each successive excess layer sits on top of the layer beneath and responds only when that layer has been exhausted (or, under a drop-down provision, is treated as exhausted).
The word “tower” is used colloquially in the market to describe the whole vertical stack. A firm with £10m aggregate cover might have a “£10m tower” built as £2m primary, £3m excess of £2m, and £5m excess of £5m — three insurers, three wordings, one programme.
Why layered can cost less than a single-insurer £10m
Excess capacity is priced against the probability of loss reaching that layer. A first-excess insurer sitting above a £2m primary is only exposed once £2m has been paid; a second-excess insurer sitting above £5m is only exposed once £5m has been paid. Each successive layer’s risk is materially lower than the layer beneath, so premium per pound of limit falls at each attach point.
By contrast, a single insurer writing a £10m ground-up policy carries the full risk from £1 upwards and prices accordingly. In many programmes, the sum of a £2m primary plus £3m XL plus £5m XL layered comes in below what a single insurer would charge to write the same £10m tower on one paper. It is not universal — primary-heavy pricing, insurer relationships and claims history all move the calculation — but it is the structural reason the layered market exists.
The layer interfaces — what to look at
Follow-form clauses
The default position at each excess layer is that the excess policy adopts the primary policy’s wording, subject to the excess’s own limit and any specific endorsements. This is “follow-form”. In a well-managed tower every layer follows the current primary. The pitfall is drift: a change of primary insurer mid-cycle, or a mid-term endorsement to the primary, that is not mirrored in the excess wording.
The discipline is straightforward. On placement of each excess layer, the broker should be able to produce a comparison showing the excess wording follows the primary as it stands today, including endorsements. On any material primary change during the year, each excess needs to be endorsed to follow.
Drop-down provisions
A drop-down clause allows the excess layer to act as primary in stated circumstances — insurer insolvency at the primary layer being the most common trigger. Without it, an insolvent primary leaves a hole that the excess is not obligated to fill.
Drop-down for primary aggregate exhaustion is a separate and more nuanced question. Where the primary aggregate is used up part-way through a policy year, the intended purpose of the excess is to respond to the next loss. Most modern PI excess wordings deal with this directly; older or thinly-drafted excess wordings do not always.
Difference-in-conditions (DIC)
Where the excess wording is not a straight follow-form — for example where the excess insurer will not follow certain primary extensions — the result is a difference-in-conditions gap. That gap can be intentional (the excess insurer is priced to reflect narrower cover) or unintentional (a drafting mismatch). Either way, the practice needs a written DIC analysis for each layer.
Aggregation across layers
Aggregation is how multiple related claims are collapsed into a single claim for the purposes of the limit. It matters at every layer.
The Supreme Court’s decision in AIG Europe Ltd v Woodman [2017] UKSC 18 remains the leading authority on the “matter or transaction” aggregation language commonly used. The essential test asks whether the underlying matters are related in a way that fits the language of the clause. On a layered programme, three points recur:
- If the primary and excess use different aggregation triggers, the same set of claims can aggregate differently at different layers — problematic in a claim.
- Where an aggregating “matter” unifies claims into a single claim at the primary, the excess layer is exposed only if that aggregated single claim exhausts the primary.
- Where the primary does not aggregate but the excess does, the excess may cap total recovery in a way that surprises the client if not clearly explained.
Reinstatement at each layer
“Reinstatement” is a policy feature that replenishes the limit after a claim has eroded it. On the primary layer, an automatic reinstatement means that after a paid claim of, say, £1m the £2m aggregate is topped back up to £2m. On excess layers, reinstatement is typically not automatic and is negotiated as a specific feature.
Where a practice is exposed to multiple claim frequency — several unrelated notifications in the same year — reinstatement at the primary matters more than reinstatement at the excess. Where the exposure is severity rather than frequency (one large loss that eats through the tower), the reinstatement question is less pressing than the total aggregate.
Notification, claims control and lead insurer
On a layered tower the primary insurer is normally the “lead” and takes claims control. In practice this means:
- Notifications go through the primary but are copied to all layers.
- The primary insurer appoints panel solicitors and manages defence.
- Excess insurers become involved once the loss is credibly likely to breach the layer beneath — typically at reserve, not just on notification.
- Settlement negotiations involving the excess require the excess insurer’s consent on any settlement that reaches its layer.
The broker’s role in a layered programme is to co-ordinate this so that notification is timely and complete at every layer — a claim that is validly notified at the primary but late at an excess can leave the client with a gap.
When a layered programme starts to make sense
Very broadly, a layered programme starts to become the natural structure once a design practice’s required aggregate reaches a level a single insurer will not write comfortably on one paper. In practice, that threshold sits around £5m aggregate for architects and engineering consultancies — but the figure is a function of the practice’s profile, not a rule. Some smaller practices with a specific high-value appointment need a layered structure at £3m aggregate; some larger practices with a benign risk profile stay on single-insurer paper at £10m.
The reasons a layered structure is chosen are typically some combination of:
- Contractual PI requirements that exceed comfortable single-insurer capacity.
- Cost efficiency of splitting the tower to reduce total premium per pound of limit.
- Diversification — spreading exposure across more than one insurer’s balance sheet.
- Availability — some sector exposures (high-rise residential, cladding-adjacent) are more readily written by excess-market participants than by the primary market alone.
What Apex does in a layered placement
Apex places layered PI programmes for architects, engineers and multi-disciplinary design firms across the UK. The broker’s work on a layered placement is not simply obtaining quotes at each level. It is:
- Presenting the risk consistently to each layer so the underwriting narrative is the same;
- Aligning wordings and identifying any DIC gaps before bind, not after a claim;
- Managing the retroactive date, notification-attachment and jurisdiction position across the tower;
- Handling notifications so that every layer is served on time and in a form that satisfies its conditions;
- Reviewing the tower at each renewal against changes in exposure — BSA 2022 progression, ARB guidance, project mix.
Speak to a named broker at Apex to discuss whether a layered structure fits your practice.
Frequently asked questions
What is a ‘layered’ PI programme?
A layered programme is a professional indemnity insurance structure in which several separate insurance contracts are stacked vertically to make up the total limit of cover. A primary policy responds first, and one or more excess policies sit above it and respond only once the layer beneath is exhausted. Each layer has its own insurer, wording and premium.
Is a layered programme always cheaper than one insurer for the same limit?
In many well-underwritten programmes, yes — excess capacity prices lower per pound of limit than primary. But it is not universal. Where the primary layer is difficult to place (owing to claims history, cladding exposure or a specific risk feature), the price efficiency of layering can narrow or reverse. The comparison needs to be run programme by programme.
What is a follow-form clause?
A follow-form clause in an excess policy means that the excess adopts the primary policy’s wording subject to its own limit and any specific endorsements. It is the standard mechanism for making sure that cover conditions align across a layered tower. The discipline is to ensure the excess follows the primary as it currently reads — including mid-term endorsements — not the primary as originally placed.
What is a drop-down clause?
A drop-down clause allows an excess layer to act as primary cover in specified circumstances — the most common trigger being insolvency of the primary insurer. Without a drop-down, an insolvent primary can leave the client with a gap the excess is not obliged to fill.
Do all layers need to share the same retroactive date?
Best practice is yes. Where an excess layer has a later retroactive date than the primary, historic exposures — especially those brought back into scope by section 135 of the BSA 2022 — may be inside primary cover but outside excess cover. Retroactive-date discipline across the tower is one of the details a broker managing a layered placement should track explicitly.
How does notification work on a layered programme?
Notifications are typically made through the placing broker to the primary insurer and copied to all excess layers simultaneously. The primary takes the lead on claims handling. Excess insurers become materially involved once the loss is credibly likely to reach their layer. The broker’s role is to ensure every layer receives valid notification within its notification requirements.
Can I have automatic reinstatement on an excess layer?
It is possible but is negotiated as a specific feature rather than a default. Excess layers typically do not carry automatic reinstatement in the way a primary policy might. Where reinstatement matters — usually because the practice’s exposure is claim-frequency rather than claim-severity — the primary layer is where reinstatement is most useful.
At what practice size does a layered programme make sense?
There is no fixed threshold. As a broad guide, a layered structure starts to be the natural answer when required aggregate limits reach a level that exceeds what a single primary insurer will comfortably write on one paper — often around £5m aggregate for design firms, but with significant variation by risk profile. Smaller practices with a specific high-value appointment may need a layer at £3m; larger practices with a benign profile may sit on single-insurer paper at £10m.
Talk to a named broker about your PI programme
Discuss primary and excess-layer options for your practice with Matt Bartlett or a member of the Apex architects team.
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