Condition inspection and hidden defects: what you do not see at the viewing (2026)

An ordinary condition inspection does not see inside a wall or a floor. It is a sensory and non-destructive inspection (KH 90-00394): the inspector looks, taps, measures surface moisture and records the risks. It only rarely confirms that damage exists, and the hidden moisture or mould damage can be exactly the one that becomes costly only after the deal. This is the most important thing to understand when buying a home: the inspection tells you where the risk is, not whether the damage has already occurred.

What a condition inspection does NOT find

The inspector does not open up walls, does not drill into the floor and does not dig the ground. That is why these regularly fall outside a sensory inspection:

What it does not see	Why	What is needed
Moisture inside a structure	The surface can be dry, wet underneath	condition survey (kuntotutkimus), opening up the structure
Condition of drainage and waterproofing	Under the ground and the slab	Digging, moisture measurement
The real age of the plumbing	Only visible from the surface	Camera survey, pipe-age data
Radon	An odourless, invisible gas	Radon measurement October to April
Risk structures in the roof and base floor	Inside the insulation	Risk-structure investigation

If the property has a known risk structure (for example a false plinth, a ground-supported floor or a 1970s to 80s structural solution), the inspector’s finding is a signal to continue to a condition survey. A condition survey is a deeper investigation, often opening up structures, that actually measures the damage. For a risk structure, a sensory inspection alone is not enough.

The buyer’s responsibility: the duty to investigate

The buyer has a duty to investigate: the obligation to study the property carefully before the deal. If the documents or the home itself show a clear sign of a problem and you do not look into it, you cannot later rely on that very point as a defect. The inspection does not remove this duty; it supports meeting it.

Use the viewing and the documents together. Ask for and read the manager’s certificate (isännöitsijäntodistus), the repair plans and any earlier surveys. If the seller or a document mentions a repair need, it passes into your knowledge, and failing to look into it becomes your risk.

Hidden defect: liability even if the seller acted carefully

A hidden defect (maakaari 2:17.1.5) means a fault that neither party knew about and could not reasonably detect at the time of the deal. The essential point is that the seller can be liable even if they acted carefully and concealed nothing. The requirement is that the property deviates significantly from what the buyer could reasonably expect, given the price and the age data.

Which law applies depends on the object of the deal:

Object	Law	Absolute complaint period
apartment (housing-company share)	Housing Transactions Act 843/1994	2 years
Real property (detached house, plot)	Land Code 540/1995	5 years

A housing-company share deal is governed by the Housing Transactions Act, and a real-property deal by the Land Code. The difference is large: the liability period for real property is longer, because faults in structures emerge slowly.

Complaint: notify within a reasonable time

A complaint means a notice of defect to the seller. It must happen within a reasonable time of when you noticed the defect or should have noticed it. In the practice of the Consumer Disputes Board, about 3 to 4 months from noticing has generally been considered reasonable. Do not wait: a complaint made too late can sink an otherwise valid claim.

On top of the reasonable time comes an absolute deadline: 2 years for a housing-company apartment and 5 years for real property from the handover of possession. After that, liability ends, even if the defect was hidden. Make the complaint in writing, describe the defect, the time you noticed it and your claim.

Radon: measure, do not guess

Radon does not show up in an inspection at all, because it is an odourless and invisible gas. The reference level for the radon concentration in homes is 300 Bq/m3, and a stricter 200 Bq/m3 for a new building. A reliable measurement is done during the heating season, October to April, with a two-month canister measurement. If you are buying in an area where radon is common, it is worth asking the seller for the measurement result or arranging the measurement yourself.

How to proceed before the deal

One next step: order a condition inspection and ask the inspector to name the risk structures separately. If the report says risk, it is a question to continue with a condition survey. Go through the following:

• Read the whole inspection report, including the risk mentions and recommendations for further investigation.
• Find out the age of the plumbing and the electrics and the repairs done, from the documents.
• Ask for a radon measurement result or arrange a measurement for the heating season.
• Check whether the deal concerns a share or real property, so you know your complaint period.
• Keep all documents and communication in writing.

The inspection and the documents are best read together, because liability for defects is determined by what you could have detected. When you gather the information carefully, a hidden defect stays the seller’s risk and does not fall on a gap in your duty to investigate.

If you want the documents and risks gone through for you, add the listing’s address to Heimer, and Heimer pulls together the property’s risks, repair needs and complaint timeline into one view.