1. The two great unknowns
These are the rule in renovation rather than the exception. A contingency therefore has to be provided.
Unforeseen circumstances, that is what only emerges when the structure is opened. And temporary works, that is scaffolding, covering, temporary heating and the organisation of access.
Both are covered from the budgeting methodology side in a separate guide, where they are named as the two largest sources of uncertainty in renovation. The second matters particularly in an occupied building, since temporary arrangements have to work for the residents and not only for the builders, and they must be shown on a separate line in the budget rather than hidden inside unit prices, because their volume depends on the programme.
2. Where the unforeseen comes from
Four sources are all hidden in the structure, and the third is common in older apartment buildings. It concerns moisture damage.
| Source | Content |
|---|---|
| Moisture damage | discovered when the facade or roof is opened |
| The condition of the load-bearing structure | including panel connections and fixings |
| Earlier alterations | which were never documented |
| The actual condition of the building services | differing from what the documents show |
Alterations made over decades are recorded nowhere. A survey reduces these sources without eliminating them, as covered by the article on technical condition.
3. How to reduce it
Four steps, and the fourth is free and rarely taken. It is asking the residents.
Carry out targeted surveys before the design rather than after. Open trial areas where there are reasonable grounds for suspicion. Gather the building's history, including earlier repairs and alterations. And ask the residents, since they know where there have been leaks or cold spots.
Information from residents does not replace a survey, but it shows where the survey should be directed. A targeted survey costs less.
4. How to handle it in the contract
Three mechanisms are all better than silence, and the second is the most effective. It concerns agreeing the contingency.
| Mechanism | Content |
|---|---|
| A contingency in the budget | whose size is justified rather than based on feel |
| Unit prices for works that may be added | for instance repairing moisture damage |
| An agreed procedure when something unforeseen appears | who decides and up to what amount |
Where the unit price is agreed beforehand, no price is negotiated mid-construction. The logic of pricing variations is covered in a separate guide on budgeting, and it applies with added force in renovation. Having a contingency meanwhile does not mean it will be spent: it means that if a problem appears, the work does not stop while funding is arranged.
5. What it means in the context of the support
Three consequences, and the third is the most serious. It concerns the payment of the support.
An unforeseen cost may not be eligible where it falls outside the approved budget. The contingency has to be covered from the own contribution where support does not cover it. And a stoppage in construction affects the deadlines, which may be fixed in the support conditions.
Overrunning a deadline may affect the payment of the support, and the conditions must be checked with the body granting the support, since they have differed between rounds. The programme has to be built with margin.
Summary and four practical rules
The two great unknowns of renovation are unforeseen circumstances and temporary works, both of which are the rule and whose volume depends on the programme. The unforeseen comes from four sources hidden in the structure, of which undocumented earlier alterations are common in older apartment buildings, and a survey reduces these sources without eliminating them. Three contractual mechanisms are better than silence, the most effective being a unit price agreed beforehand, since no price is then negotiated mid-construction.
Four rules: show temporary works on a separate line in the budget. Agree unit prices for works that may be added. Justify the size of the contingency rather than taking it from feel. Ask the residents before directing the survey.
This article offers professional orientation as at the date of verification. It is not a quotation.