A manufacturer we knew had separated his finances carefully — the business in a company, the family home in his wife’s name, savings in mutual funds. He felt protected. What he had forgotten was a stack of papers signed years earlier: personal guarantees on the company’s loans, given almost as a formality when the bank asked. When a large customer defaulted and the company’s cash ran dry, the bank did not stop at the factory gate. It came for everything he had personally guaranteed. The wall he thought stood between the business and the family had a door in it — and he had signed it open.

This is the most common gap in a business family’s defences. The company may have limited liability; the founder, through personal guarantees and informal lending, usually does not.

A company can fail without ruining a family. A personally guaranteed company failing usually takes the family down with it.

How the wall gets a door in it

It happens quietly, through ordinary decisions. A personal guarantee on every working-capital loan. Family money lent into the business during a cash crunch and never formally returned. The family home pledged as collateral for an expansion. Each was reasonable in the moment; together they erase the very separation that limited liability was meant to provide. When trouble comes, there is no longer a business balance sheet and a family one — only a single pool the lenders can reach.

Rebuild the wall on purpose

The work is to make the separation real again. Know exactly what you have personally guaranteed, and renegotiate or retire those guarantees as the company strengthens — banks will often relax them once the numbers allow. Keep a genuine pool of family wealth that is diversified, liquid, and never pledged to the business, so a bad year in the company cannot reach it. Formalise any money that moves between you and the firm. The goal is simple: the business should be able to fail without taking the house, the school fees and the retirement with it.

You took the risk to build something; that is the founder’s job. Just make sure the risk stays inside the walls of the thing you built. Protect the family balance sheet as deliberately as you grow the business one. In two decades, the founders who slept soundly through a bad year were the ones who had quietly put part of the family beyond the reach of the business — long before they needed to.