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Basement and empty property monitoring
Everything else we install is passive. A membrane cannot tell you it has been punctured and a sump cannot tell you it has stopped — you find out when the floor is wet, which is usually months after the thing that caused it. Monitoring is the part that closes that gap: wireless sensors around the property, a gateway with its own mobile connection, and an alert on your phone the day something changes.
The system in section
What is actually behind the wall.
- 4G gateway, upstairs. One per property, and the only part that talks to the outside world. It carries its own mobile connection, so nothing here depends on your broadband, your Wi-Fi or a phone line — which matters most in exactly the two cases this is for: a basement, and an empty house.
- Power monitoring at the consumer unit. Loss of mains is raised as an alert in its own right. For a sump that is the failure that counts, and the storm producing the water is usually the same event as the cut that stops the pump.
- Temperature and humidity in the room. The slow one. A basement creeping up in humidity after a shower room or a gym goes in is a ventilation problem you can still fix cheaply; the same reading unnoticed for two winters is a mould problem you cannot.
- Leak detection cable along the channel. A run rather than a row of pucks, so water is caught anywhere along its length instead of only where a sensor happens to sit. It follows the perimeter channel and the floor's low line — positions that are only reachable while the floor is open.
- Level sensing at the sump. Watches the thing the whole drained system depends on. A chamber filling when it should be emptying is a pump that has stopped, and you are told that evening rather than the following February.
- Automatic shut-off on the incoming main. Optional, and subject to the plumbing suiting it. Where it fits, a leak does not just raise an alert — the supply closes behind it. On a finished basement the damage is done by volume, not by the first cup of water.
- Wall surface probe. Reads the temperature of the wall itself, which is the half of the condensation question a humidity sensor cannot answer. What decides whether a wall wets is the gap between the dew point of the air and the surface it touches.
- Power monitoring on the pump. Not the same as item 2. That one says the house has power; this one says the pump actually used it — how often, for how long, and how hard. A pump working twice as hard in June as it did in March is telling you something months before it fails.
Who built it, and why it is worth saying
We did not build this on our own. NocNoc are property monitoring specialists — their work is watching empty and vacant buildings, and they had a proven system for it long before we spoke to them. What they did not have was a reason to think about basements.
That is what we brought: where water actually appears below ground, what a sump failure looks like in the hours before anyone notices, which readings matter in a room built to Grade 3 and which are noise. Between us we adapted their system for the thing we do. They run the platform; we design where it goes and fit it. You can read their side of it at nocnoc.uk.
You deal with us. We survey it, we install it, and we invoice it — one contract and one number to call. NocNoc sit behind the platform rather than in front of you, so there is no second supplier to chase when you want a sensor moved or an alert sent to somebody else.
What is actually being watched
Escape of water. Leak sensors at the stopcock, the plant, and the low points of the floor — the places water shows up first and the places nobody looks.
Damp and frost. Temperature and humidity in the room itself. A basement creeping up in humidity after a gym or a shower room goes in is a ventilation problem you can still fix cheaply; the same reading ignored for two winters is a mould problem you cannot.
Power failure. Treated as an alert in its own right, and for a sump this is the one that matters most. A pump with no power is not a pump. The storm that produces the water and the cut that stops the pump tend to be the same event.
Fire, gas and unauthorised access. Raised off-site, so an alarm sounding in an empty house is heard by somebody.
A timestamped record. Every reading kept, so the condition of the property is evidenced rather than remembered.
A leak alert that also turns the water off
Where the plumbing suits it, an automatic shut-off valve can go on the incoming main. A leak is then not just reported — the supply closes behind it. On a finished basement, where the damage is done by volume rather than by the first cup of water, that is the difference between a call-out and a claim.
It is an option rather than a default, because it depends on the stopcock being somewhere sensible and the pipework being in a condition worth valving. We will tell you at survey whether yours is.
Fitted while the floor is open
The right time to do this is during the waterproofing works. The sump is accessible, the floor is not yet screeded, and cable routes and sensor positions can be chosen rather than worked around. Retro-fitting to a finished room is possible and we do it, but it is a worse job for a worse price.
If you are having a basement done, decide about monitoring before the screed goes down rather than after.
Where you actually see it
As standard it is a web dashboard: one view per property, a daily status email confirming everything is as it should be, and immediate alerts by email or SMS when it is not. You choose who gets told what — an agent, a neighbour and an owner abroad can all be on different alerts.
It does not have to stay in somebody else's app. If you already run Home Assistant, the sensors can be brought into it, so the basement sits alongside the rest of the house rather than in a separate login you forget you have. For a portfolio, or for anything unusual, NocNoc will build a custom app around it.
That flexibility is the part most systems get wrong. A monitoring system you have to remember to open is a monitoring system you stop looking at, which is why the alerts matter more than the dashboard and why the dashboard should live where you already are.
How the alert reaches you, and what it says
An alert goes out on two independent paths: a plain text message, and a notification to the app. The text matters more than it sounds — it needs no app installed, no smartphone and no account, so it works for an owner who wants nothing to do with software, and it works on a managing agent's duty phone that gets handed between people. Two paths also means one of them can fail and you are still told.
If you run Home Assistant, the serious alerts can be sent as critical notifications. Those are the ones iOS allows through the silent switch and Do Not Disturb — so a leak at three in the morning is not politely held back until you happen to pick the phone up. For the situation this whole system exists for, an alert that respects your silent switch is not worth having.
The wording is deliberate too. Alerts say what would innocently explain the reading alongside what would not — movement with no door opening beforehand is either somebody already inside or an interior false trigger, and the message says so. A system that cries wolf is one you mute within a fortnight, and a muted system protects nothing.
When the house is empty
This is where the system started, and it is a service in its own right — we will fit it to a property with no waterproofing work attached at all. An empty house is where small problems become expensive ones: a leak running for six weeks, a heating failure in January, a burst after a frost, a door left open by a contractor.
It suits overseas owners, probate sales, a refurbishment between trades and a let between tenancies. There is no broadband, Wi-Fi or phone line required — the gateway carries its own 4G, so it works in a house with the power on and nothing else. Around ten to twelve sensors suits a typical three or four bedroom property.
The hardware is yours outright. When the property is sold or re-let, it comes out and goes into the next one. You are not renting equipment you will never own.
What it costs
Installation is £400 + VAT, covering fitting the gateway and the sensors, testing every alert, and setting up who gets told what. That is our figure and it is the same whether it goes in with a basement job or into an empty house on its own.
The hardware itself is typically £300 to £450 for a three or four bedroom property, depending on how many sensors the building actually needs — it is specified at survey, not sold as a fixed bundle. Monitoring and the dashboard are £50 + VAT per property per month, which covers the mobile data, the alerts, the daily status email and ongoing support.
Hardware figures are indicative as at August 2026 and can move with availability; everything is confirmed in writing after the survey. Optional extras — automatic water shut-off, battery backup, solar power for a property with no supply, a Home Assistant or custom dashboard build — are priced once we know whether you actually need them. It all comes on one invoice from us.
Illustration · simulated readings
What you actually look at.
Sump — water level
Normal
Pump last ran 2 h ago, for 38 s
Pump — cycles / 24 h
6
Four to nine is normal for this site
Perimeter channel
All dry
Checked 42 s ago
Basement air
17.4 °C
Wall surface probe reading 13.0 °C
Relative humidity
72 %
Dew point 12.3 °C — only 0.7 K below the wall. Alert sent 09:14.
Mains power
On
Battery backup 100% · last outage 14 June
What goes where
Every sensor, and what it is there to catch.
The sensors are Zigbee — a low-power radio standard built for exactly this, where a battery has to last years and the device only has a few bytes to say. That matters more below ground than anywhere else in a house, and it is the reason the schedule ends with two devices that measure nothing at all. A basement gets what it needs rather than a fixed bundle, so not every line below appears on every job; the ones that do are decided at survey, and the reasons are written down.
S1
Sump level
A chamber filling when it should be emptying — the plainest evidence that the pump has stopped.
In the sump, above the normal water line
S2
Pump power monitor
The current the pump draws, so it is on record that it ran, how long for, how hard — and, the one that matters most, that it did not run when it should have. A blocked impeller pulls more current than a clear one.
On the pump's own supply
S3
Leak detection cable
Water anywhere along its length rather than at one point, which is what lets it follow the perimeter channel and the floor's low line.
Laid in the channel while the floor is open
S4
Leak sensors
First water at the places it tends to appear before anywhere else — the stopcock, the plant, under a boiler.
At the fittings, not spread evenly
S5
Air temperature and humidity
The slow problem. A room creeping up after a shower room or a gym goes in is still a ventilation fix; two winters later it is a mould one.
On the wall, away from the door and the plant
S6
Wall surface probe
The temperature of the wall itself, which is the missing half of the condensation question — what decides whether a wall wets is the gap between the dew point of the air and the surface it touches, not the humidity reading on its own.
Against the wall face, behind the finish
S7
Vibration
That the pump physically moved water rather than merely being switched on. Read alongside S2 it separates a working pump from a seized one that is still drawing power.
On the pump body
S8
Contact
That the chamber was opened, and when — which over a few years is the maintenance record a Type C warranty usually depends on.
Sump lid, or the plant room door
S9
Mains power
The cut itself, raised as an alert rather than inferred from silence. For a sump the loss of power is the failure.
At the consumer unit
S10
Smoke, gas and access
Fire, gas and an opened door in a building with nobody in it to hear the alarm.
As the property needs
GW
4G gateway and battery backup
Nothing — it is the only part that talks to the outside world, and the backup is what keeps it talking through the power cut that caused the problem.
Ground floor, where the signal is
RT
Mesh routers
Nothing either. Mains-powered relays that keep everything above in range of the gateway. See the note below — in a basement these are not optional.
Top of the basement stairs, and inside
Why the radio decides where this gets fitted
A basement is the worst radio environment in a house. Reinforced concrete both absorbs and reflects at 2.4 GHz and the rebar behaves like a Faraday cage, with the boiler, the tanks and the consumer unit making it worse. A sensor that pairs perfectly on the bench can be unreliable once the floor is down.
Only mains-powered Zigbee devices relay for the others; a battery sensor never does. So the mesh needs a router at the top of the stairs and a second one inside the basement, placed either side of a thick wall rather than trying to push a signal through it.
That is an argument for fitting this during the works, and it is the honest reason we push for it. We are on site with the floor open, the first fix reachable and the sockets not yet finished, so routers and cable go where they need to go. Someone arriving at a finished basement afterwards is choosing between the positions that are left.
What this is not
None of it is structural crack monitoring. A vibration sensor reports that something moved; crack monitoring means a tell-tale gauge read to a fraction of a millimetre over months, and the two get confused because the sensors are cheap and the words sound close. If movement is the actual worry, we will quote that separately as the different job it is.
And every sensor is a battery that will eventually go flat, faster in a cold basement than in a warm loft. We set the low-battery warning early rather than at the last minute, and the replacement visit is part of the service rather than a surprise — a monitoring system with three dead sensors in it is worse than none, because you think you are covered.
Common questions
What people ask us about basement monitoring.
Are these Zigbee sensors, and can I use my own?
They are Zigbee, which is the same standard most smart-home kit uses — so if you already run Home Assistant the sensors can join what you have rather than sitting in a separate system. Bringing your own is usually possible and occasionally a false economy: the parts are cheap, and what you are paying us for is knowing which ones a basement needs, where they go and what threshold turns each one into an alert worth reading. Tell us at survey what you already own and we will tell you honestly whether it is worth keeping.
Do I need broadband or Wi-Fi in the basement?
No. The gateway has its own 4G mobile connection, which is deliberate — a basement is exactly where domestic Wi-Fi is worst, and an empty property often has no broadband at all. It also means the monitoring does not stop when the router is unplugged or the account is closed between tenancies.
What happens if the power goes off?
The power cut is itself one of the alerts, which is the point — for a sump, loss of power is the failure. Battery backup keeps the gateway reporting through it, so you are told rather than left with a system that went quiet at the moment it mattered. For a property with no mains supply at all there are solar and battery options.
Will my insurer accept this?
It helps, and the timestamped history is the useful part — you can show the condition of the property over the whole period rather than arguing from memory. But be clear on what it is: monitoring supplements the inspections or conditions your policy requires, it does not replace them, and the terms of cover remain your insurer's decision. Ask them directly before assuming a discount.
Can you monitor a basement you did not waterproof?
Yes, and a fair number of the ones worth monitoring are somebody else's system that nobody has looked at in years. We will survey what is there first, because there is no sense alerting you about a system that already needs work — occasionally the honest answer is that the money is better spent on the pump than on watching it.
Will it wake me if my phone is on silent?
Every alert goes out as a text message as well as an app notification, so it reaches you without depending on an app being installed or a phone being unlocked. If you run Home Assistant, the serious alerts can additionally be sent as critical notifications — the type iOS allows through the silent switch and Do Not Disturb. Given that most of what this system catches happens overnight or while a property is empty, that is worth setting up properly at handover rather than discovering the first time it matters.
Can I see the sensors in Home Assistant?
Yes. The standard web dashboard suits most people, but if you already run Home Assistant the sensors can be brought into it so the basement appears alongside everything else in the house. For a portfolio or an unusual requirement a custom app can be built instead. Tell us at survey which you want, because it is cheaper to plan for than to add later.
Who do I pay, and who do I call?
Us, for both. We survey it, install it and invoice it, so there is one contract rather than two. NocNoc run the monitoring platform behind it — they are credited because it is their system and it would be dishonest not to say so, but they are not somebody you have to deal with.
Is there a long contract?
The hardware is bought outright and belongs to you, so what you are committing to is the monthly monitoring rather than the equipment. If you stop, you keep the kit and it can be redeployed to another property.
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Where we work
Across London and Surrey.
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Tell us what you're seeing and we'll tell you honestly whether it needs a full system or something much simpler.