Look for fresh paint patches on ceilings, tide marks low on walls, warped or replaced flooring and new kitchen plinths. Ask directly about past leaks and insurance claims. On a second viewing, check the water meter with every tap off and the boiler pressure gauge. Where the signs add up, a pre-purchase leak survey settles it before exchange.
A viewing lasts twenty minutes. The house has been tidied, aired and, quite possibly, painted. Sellers are not obliged to point at the ceiling and tell you what happened there last winter. So the clues that a house has had a leak, or still has one, are for you to spot, and most of them are small. This guide lists what we look for when we walk into a property, what to ask the agent, and the two-minute checks on a second viewing that tell you whether water is still moving somewhere it should not be.
Ceilings first
Look up in every room, particularly below bathrooms and below the loft hatch. Old leaks leave brown or yellow rings; a fresh coat of emulsion over one ring stands out as a slightly brighter, flatter patch on an otherwise aged ceiling. Run a torch across the surface at a low angle and the difference in texture shows up. A ceiling that has been entirely repainted in a house where nothing else has is worth a question.
Look for slight sag or a hairline crack in a line, which suggests plasterboard that got wet and was left in place. Check downlights and ceiling roses for discolouration around the edges. Our article on a ceiling stain when the loft is dry explains why the stain is often nowhere near the source.
Low on the walls
Crouch down. The bottom metre of wall is where leaks and damp both show. Look for:
- A tide mark, a faint horizontal or arched line where the plaster changed colour. A flat line the same height along a wall points to rising damp. An arc rising from one spot points to a pipe leak.
- Blistered or flaking paint just above the skirting, and a fluffy white salt deposit on the plaster.
- Swollen skirting, soft to press, or skirting that is obviously newer than the rest of the room.
- Furniture placed oddly. A bookcase against a wall in a room with no other reason for it, a rug in a hallway. Ask to look behind and beneath.
- Mould in the corners of a room, particularly behind curtains and in built-in cupboards.
Old Cornish cottages, granite or cob, very often have some damp low on solid walls and it is not necessarily a leak. The distinction matters for what you will be able to claim later, and we have written about how to tell rising damp from a leak in a Cornish cottage.
Floors
Walk every room without shoes if you can. Feel for a soft spot, a bounce or a dip in a timber floor, and for a cupped or lifting edge on laminate or engineered boards. Look along the floor towards a window and cupped boards show as ripples. A section of flooring that is newer than the rest, especially in a hallway or kitchen, was replaced for a reason. On a solid floor, a dark patch on bare concrete or a tile that sounds hollow when tapped can indicate moisture beneath.
In kitchens, look at the plinths under the base units. New plinths against old units, or a plinth that has swollen at the bottom edge, is one of the most reliable signs of a leak that has been dealt with quickly and cheaply. Pull one off if the seller allows it; the floor behind tells the whole story.
Bathrooms and the airing cupboard
Press the sealant round the bath and shower. Black mould in a line along it, or a gap, means water has been getting behind. Check the floor by the toilet and at the corner of the shower tray for soft vinyl or lifted tiles. Open the airing cupboard: staining on the floor of it, corrosion on cylinder fittings, or a smell of damp all point to a slow drip that has been running for a while. A cylinder with fresh green or white deposits at a joint is dripping now, not historically.
The boiler and the meter
Two gauges tell you more than the whole rest of the house.
The boiler pressure gauge
A sealed heating system should sit at about 1 to 1.5 bar when cold. If the needle is near zero, or the seller mentions topping it up, the system is losing water. That could be a weeping valve or it could be a heating pipe under a floor. Ask when it was last topped up and how often. A filling loop that is left connected with the tap worn is a giveaway.
The water meter
Most Cornish homes are on a South West Water meter, usually in a box at the boundary or just inside the property. On a second viewing, ask the agent if you can read it, note the number, make sure nothing in the house is running, and read it again at the end of the viewing. Half an hour is enough to catch a meaningful leak; the small dial or the last digits should not move at all. Our guide to a meter moving when nothing is on explains how to read it. For a house with a long private supply pipe from the lane, which is common on farms and rural properties across the county, this check matters more than anything inside the building, because a leak on that pipe is the buyer’s to fix and pay for once the sale completes.
Outside
Walk the boundary. A green, lush strip in an otherwise dry lawn, a patch of ground that stays soft in summer, or moss on a path along the line between the meter and the house all suggest a leaking supply pipe. Look at the stop valve chamber at the boundary: standing water in it can be rain, or can be a leak. Check the ground level against the damp course line on the outside walls, and whether a later path or patio has been laid above it.
Questions to ask the agent and the seller
- Has the property had any water leaks or escape of water? A direct question that must be answered honestly on the property information form anyway.
- Have there been any insurance claims in the last five years? Buyers’ insurers will see them on the industry database regardless.
- Why was this ceiling or floor replaced? Point to the patch and ask.
- How often does the boiler need topping up?
- Do you have the leak detection report, plumber’s invoice and drying certificate? A seller who has these hands them over. One who does not may not have dealt with it properly.
- Has the house been empty for long periods? Holiday lets and second homes left unheated over winter are where frost damage and unnoticed leaks happen.
| What you notice | What it may mean | What to do |
|---|---|---|
| Fresh paint patch on an old ceiling | Repaired leak above, cause unknown | Ask what happened and for the paperwork |
| Tide mark or blistering low on one wall | Pipe leak under the floor, or rising damp | Check the meter and boiler gauge |
| New plinths or a section of new floor | Leak dealt with cheaply, may not be dry | Look behind, ask for a drying certificate |
| Boiler pressure low, filling loop worn | Heating system losing water | Ask how often it is topped up |
| Meter moves with everything off | Live leak on the supply or plumbing | Commission a leak survey before exchange |
| Green strip in the lawn along the pipe line | Leaking underground supply pipe | Meter test, then a survey |
When to have a pre-purchase leak survey
A standard homebuyer report takes moisture readings at the surface and flags anything high for further investigation. It does not find the leak. If the signs above add up, or the meter moved, or the seller’s answers were vague, a specialist survey before exchange tells you what you are actually buying. We use thermal imaging to map the wet areas behind ceilings, walls and floors without opening anything, moisture meters to measure how far it extends, and acoustic and tracer gas methods to pin a live leak to a point.
The result is a written report you can use three ways: to walk away, to negotiate the price down by the cost of the repair and drying, or to go ahead with confidence knowing the patch on the ceiling really is history. Compared with the cost of discovering a saturated floor under a new kitchen in a house you have just bought near Wadebridge, it is a small piece of the budget. We carry out leak detection across Cornwall and can normally fit a pre-purchase survey around the conveyancing timetable.
Frequently asked questions
How can I tell if a house has had a water leak?
Look for fresh paint patches on ceilings, tide marks or blistering low on walls, cupped or replaced flooring and new kitchen plinths. Ask the seller directly about leaks and insurance claims; the property information form requires an honest answer. Low boiler pressure and a moving water meter suggest a leak that is still live.
Will a surveyor find a hidden leak?
A homebuyer or building survey takes surface moisture readings and flags high ones for investigation, but it does not locate the source. If the readings are high or the signs add up, a specialist leak detection survey with thermal imaging and moisture mapping is the next step, and it can be done before exchange.
Should I buy a house that had a leak?
Usually yes, if the leak was found properly, repaired and dried, and the seller can show the report, invoice and drying certificate. The risk is a leak that was patched over without finding the cause. If the paperwork is missing, have the area surveyed and price accordingly.
Can I test the water meter on a viewing?
Yes, with the agent’s agreement. Read the meter with every tap and appliance off, wait for the length of the viewing, and read it again. Any movement means water is flowing somewhere. It is the single most useful check you can do in a property with a long supply pipe.
Who pays for a leak found before completion?
The seller owns the problem until completion, so a leak found by your survey is a matter for negotiation: they fix it, or the price reflects the cost. After completion it is yours, including a leak on the private supply pipe between the boundary and the house.
Survey before you sign
If something on the viewing did not add up, we can survey the property before exchange, map what is wet, find any live leak, and give you a report to negotiate with or walk away on.
