Building a renovation budget with the right contingency

A renovation budget for an old property is built lot by lot, never as a single global figure. Each lot, from structural work to finishes, carries its own risk of drift. So, before the first quote, you set aside a contingency dedicated to surprises: in an old building, invisible hazards are the rule, not the exception. Finally, you track every amount committed against the initial budget, up to handover of the works.

Why break the budget down by lot rather than one global figure?

A global figure is appealing: it gives the illusion of a simple frame. But it says nothing about what you are buying, it makes quotes impossible to compare and it hides the trade-offs. The day a surprise appears, you no longer know which line should pay for it, or what to sacrifice to cover it.

Breaking the budget down by lots answers these three weaknesses. It makes quotes comparable, since every tradesman prices an identical scope, described in a single brief. It makes trade-offs possible, because you can move the boundary between the essential and the desirable lot by lot, without touching the rest of the project. And it keeps the follow-up readable: at any moment, you know which share of the budget is committed, paid, or still to pay.

The structure is stable from one project to the next: structural work, electrics, plumbing, heating and ventilation, finishes, and one last line that is far from the least important, the contingency for surprises. It is the common foundation of the guides in the Travaux & rénovation category, and the framework we suggest you follow. For the items that surround the works, property price, acquisition fees, annual costs, the budget simulator completes this framework. One line is almost always missing from this foundation: the damage-to-works insurance, compulsory as soon as the works fall under the ten-year guarantee.

What does each lot contain, and which hazard comes with it?

A lot is a package of works entrusted to one trade, with its materials, its constraints and its risks. Here is the reading grid, with the typical hazard to watch on every line.

Lot	What it includes	Typical hazard
Structural work	demolition, partitions, masonry repairs, openings	floor or load-bearing walls to reinforce, degraded masonry discovered on opening-up
Electrics	consumer unit, circuits, sockets, lighting, earthing	ageing buried circuits, ducts to recreate, protections to upgrade
Plumbing	water supply, drainage, taps, sanitary fittings	embedded pipework to replace, blocked or worn drains
Heating and ventilation	heat production, emitters, ventilation network	flues to clean or reline, radiators to replace
Finishes	painting, floors, joinery, wall coverings	surfaces needing more preparation than planned, doors to refit
Contingency	a separate reserve, fixed in advance and unallocated	damp, wall linings to redo, hidden services

The last line reads like the others: a scope, a rule of use, a discipline. It is neither a kitty for last-minute whims nor a mattress to be opened the first time a lot slightly overruns. It is a technical reserve, justified by the nature of old buildings.

Why do old buildings hide invisible hazards?

Three families of hazards explain most of the drift seen in old properties.

Hidden services, first. Electrics, water supplies, drainage: in an old building they run inside walls, floors and false ceilings, often for decades, sometimes in materials no longer in use. As long as the wall is closed, everything seems fine; the moment it is opened, the picture changes. A circuit buried under plaster, a drain connected any old how behind a cupboard: discoveries that only appear once the works begin.

Wall linings and light partitions, next. Fitted over successive waves of previous works, they sometimes conceal disorders: trapped damp, attacked timber, cracked masonry, abandoned ducts. Redoing them costs more than dressing them up, and that cost is invisible until they are dismantled.

Damp, finally. Rising through walls, slowly seeping around joinery or a terrace: it hides under the paint and reveals itself as soon as you heat, insulate or close the home up. A property left vacant gladly delivers this kind of surprise, precisely when a new owner launches a renovation. Before demolition, some period materials also call for regulatory checks, which translate into precautions and sometimes extra steps.

These hazards justify the contingency. From abroad, you cannot pop in to look behind the cupboard or under the floorboards: the contingency is your peace of mind. Our advice on running building works from abroad covers this remote organisation in depth.

Set the right contingency aside, then leave it alone

The contingency is fixed at the same time as the budget, not when the surprise arrives. You express it as a share of the total budget, you record it as a line of its own, and you mention it to the tradesmen: a craftsman who knows a reserve exists works differently from a team that believes the budget is locked.

Its rules of use come down to three:

• it only funds a genuine surprise, discovered on site and documented with photos and in writing;
• every draw on it is justified, dated and tied to the lot concerned;
• whatever is left at handover stays yours: it is not a hidden budget to upgrade the finishes.

In exchange, never dip into it for a more ambitious choice of tiling or kitchen. The temptation is always there, and it is fatal: a contingency spent on extra comfort no longer exists on the day damp appears behind the lining.

Phase the works to spread the financial effort

A budget is not built only in columns, it is built in time too. Phasing orders the campaigns of works by priority: safety first, with electrics and plumbing; comfort next, with heating, joinery and insulation; finishes last, which only make sense once the services are secure and the walls closed.

This sequence has three budget virtues. It spreads the effort: each phase is funded close to when it starts, rather than committing everything at once. It allows re-estimating: between two phases you know your building better, and you price the next steps with more accurate quotes. It protects: you never pay for finishes that a later phase of works might damage.

For a non-resident owner, phasing also simplifies logistics: access to the property, inspection visits, rental or occupancy periods. Some expenses, finally, arrive from outside: when the co-ownership votes a façade redecoration, it joins your budget plan without waiting for your calendar. Far better to have anticipated it in the phasing.

How do you track commitments against the budget during the works?

The budget lives during the works: every quote approved, every deposit paid, every invoice settled moves the lines. Keep a simple tracking table, lot by lot: initial quote approved, amounts committed, amounts paid, remaining to pay. Three habits keep it honest:

• every extra goes through a signed document before execution, never through a word on the phone;
• every payment is tied to a dated record: quote, works statement or invoice;
• every gap between committed and budget is noted and decided: one lot is arbitrated to keep another on track.

This follow-up takes a regularity that distance makes harder: time differences, missed calls, photos that arrive late. If you cannot maintain it yourself, works coordination, quoted in advance, carries this follow-up for you: French Realty informs and coordinates, the tradesmen carry out the works, and you keep every decision.

A renovation budget is not a figure set at the outset, it is a thread you hold to the very end. Every old property has its hidden services, its damp patches, its mysterious wall linings. To build a budget that takes your property, your priorities and your calendar into account, the personal study offered by French Realty frames all of this with you, with full knowledge of the facts.