Wi-Fi weak upstairs? Why floors block it and what helps
The signal that crosses two walls downstairs barely makes it through the ceiling. A floor is heavier than a wall, the signal crosses it at an angle, and router antennas point the wrong way. Each of those has a fix.
In short
- A concrete floor slab can cost 15 to 30 dB at 2.4 GHz, more than most walls, and a router in a downstairs corner reaches upstairs rooms at a slant, through even more of it.
- In a house on two floors the router should be near the middle of the house, close to the ceiling downstairs or low upstairs. The stairwell is the easiest way up.
- If the room directly above the router is fine and the far rooms aren't, move the router. If the whole upper floor is weak, you need a second access point upstairs, ideally on a cable.
- Lofts are hardest: two floors away and often lined with foil-backed insulation, which reflects Wi-Fi like metal.
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In houses on more than one floor this is the most common complaint of all: the router is downstairs, where the line comes in, the bedrooms and the study are upstairs, and the Wi-Fi that happily crosses two walls on the ground floor barely makes it through the ceiling. The router isn't faulty. Floors are simply the hardest thing in a home for Wi-Fi to cross, for three separate reasons.
Why a floor costs more than a wall
It's heavier. Most interior walls are plasterboard, light block or brick. Floors are joists and boards with insulation, or in many houses a concrete slab with steel mesh inside. In NIST's laboratory measurements, 10 cm of concrete cost about 15 dB at 2.4 GHz and 20 cm about 29 dB, compared with about 6 dB for brick and 1 dB for plasterboard. Every 3 dB halves the signal, so a slab can leave a small fraction of what reached the ceiling. Underfloor heating pipes or a foil-backed insulation layer make it worse.
The angle makes it thicker. A router in a downstairs corner reaches a bedroom on the other side of the house at a shallow angle. At 30° above horizontal, the signal travels through twice the slab's real thickness; at 15°, almost four times. The same floor that costs little straight above the router costs a great deal on the diagonal. This is why the room directly above the router is often fine while the far rooms aren't.
The antennas point sideways. Router antennas radiate in a ring around themselves, strongly outward and weakly along their own length. A router with every antenna standing straight up sends the least signal toward the floor above.
Find out which kind of problem you have
Take a signal reading in three places upstairs: the room directly above the router, the top of the stairs and the room furthest away. Wi-Fi not reaching one room explains how to read the signal on iPhone, Mac and Android.
If the room above the router reads well and the far rooms don't, the problem is distance and angle, and moving the router toward the middle of the house will help a lot. If the top of the stairs is good but the rooms around it aren't, the stairwell is carrying the signal and the slab is blocking it everywhere else; a second unit on the landing will cover them. If all three are weak, the floor is the barrier and the upper floor needs its own access point.
Where the router should go in a house on two floors
Picture the router's coverage as a rough sphere, squashed by every floor and wall it meets. You want it near the middle of the whole house, not just the middle of the ground floor. That leaves two good options: high on the ground floor near the centre, on a tall shelf or wall-mounted near the ceiling, or low on the upper floor above the centre, on a low shelf in a central room or on the landing. Either way the signal crosses the slab close to vertically instead of at a slant from a corner.
Which floor to favour depends on where the demanding use is. A home office or a games console upstairs, with the TV downstairs on a cable, points upstairs. A household that lives downstairs and only sleeps upstairs points downstairs. Devices on a cable don't care where the router is, so wiring the TV or the computer frees the router to move toward the wireless devices.
If the line comes in at the wrong end of the house, a long Ethernet cable from the socket, along the skirting boards and up the stairs, gets the router where it needs to be. Where to put the router covers the rest: height, cabinets, what to keep away from it.
Two free adjustments
Use the stairwell. It's the only opening in the slab, and signal travels up it far more easily than through concrete. A router near the bottom of the stairs, or a central router with the stairwell on its way to the upper rooms, helps the whole upper floor.
Tilt the antennas, if the router has external ones. TP-Link recommends keeping them vertical for one floor and angling them at about 30° when the signal needs to reach another floor. Tilting moves some coverage up or down at the expense of your own floor, so check the rooms on both floors afterwards.
When the router can't cover both floors
An access point upstairs on a cable is the fix that ends the problem. If a cable can go up beside pipes, inside a cupboard or along an existing conduit, an access point or a wired mesh node gives the upper floor its own full-strength Wi-Fi.
A mesh node on the landing is the usual answer when a cable can't go up. The landing still receives the router through the stairwell and sits close to the upstairs rooms. Don't put the node in the far bedroom: it would receive a weak signal and pass on a weak signal. Where to put a mesh node explains how to find the spot.
Powerline adapters can carry the connection upstairs over the electrical wiring. Upstairs rooms are sometimes on a different circuit, which can slow them down, so test before you rely on them.
A newer router in the same downstairs corner rarely helps. Regulations cap how much power any router may transmit, and concrete costs the same whichever router is in front of it.
Lofts and attic rooms
A loft conversion is often the hardest room in the house. It's two floors above a ground-floor router, at a steep angle through two slabs. The stairs up to it are usually narrow, so there's little of the stairwell effect. And many loft conversions use insulation boards or roof membranes with a reflective aluminium layer, which keeps heat in and reflects Wi-Fi like a sheet of metal. If the floor was insulated the same way, the room sits inside a metal-lined box.
What works: bring the router or the main mesh unit up to the first floor, close to the loft stairs, so the loft is one floor away instead of two; or, better, run a cable up and put an access point in the loft itself. During a conversion is the time to pull that cable. Afterwards, look for routes that already exist: service risers, an old chimney void, cupboards stacked one above the other.
What doesn't: an extender inside the loft, repeating a router it can barely hear through foil and two floors, or a stronger router downstairs. A foil layer doesn't care how much power arrives at it.