Wi-Fi Won't Reach Upstairs

Almost always: the router is on the ground floor, near a wall, low down, and the 5 GHz band cannot survive both the floor and the distance. The 2.4 GHz band does get upstairs, which is why you are still "connected" up there and nothing works properly.

Why this happens

Vertical coverage is genuinely harder than horizontal

A router's antennas radiate in a doughnut shape around their own axis. Vertical antennas therefore push signal outward strongly and upward weakly — the weakest direction is straight off the tip. A router sitting upright on a ground-floor shelf is optimized for exactly the floor it is standing on. Add a floor structure with joists, insulation and sometimes a layer of screed, and the upper floor is working with what leaks through.

The corner problem compounds it

Routers live where the cable enters, which is usually an outside wall. So the signal reaching your upstairs back bedroom has crossed a floorand the longest diagonal in the building. Either alone is survivable. Together they are not.

Your devices cling to the wrong band

Many phones and laptops hold onto a 5 GHz connection well past the point where it is useful, rather than dropping to a slower but healthier 2.4 GHz link. The result is a device showing full signal and moving almost no data. This is a client-side decision your router only partly influences.

How to tell it is this and not something else

1. Speed test at the bottom of the stairs, then the top. A big drop over that short distance is the floor, not the distance.
2. Check which band you are on upstairs. If you are on 2.4 GHz up there and 5 GHz downstairs, that confirms it — the fast band is not making it.
3. Stand directly above the router, upstairs. If that spot is fine and the far bedroom is not, it is distance on top of the floor. If even the spot directly above is poor, it is the floor structure itself, and there may be foil-backed insulation or metal lath in it.
4. Try one device sitting on the landing floor versus held up. A noticeable difference at waist height tells you how marginal the link is.

Fixes, cheapest first

1. Raise the router and move it toward the middle of the ground floor. Free. Gets the signal out of the furniture and shortens the worst diagonal.
2. Angle some antennas out to 45 degrees or flat. Free. Trades a little horizontal reach for real vertical gain.
3. Give 5 GHz its own network name and pin the upstairs devices to 2.4 GHz. Free, and counter-intuitive: a reliable slow link beats an unusable fast one for calls and streaming.
4. Relocate the router upstairs over one Ethernet run. The cost of a cable, and the best value fix on this list.
5. Add one mesh node on the landing. The standard answer when relocating is not possible. Put it roughly above the router, not in the far bedroom.
6. Add a wired access point on the landing or ceiling. If cabling is possible, this beats everything else outright — see using a real access point at home.

If you need hardware, pick by what you can cable

The decision is almost entirely about cabling, not about brands.

Sizing the mesh option properly is a square-footage question rather than a brand question: how many nodes do you need. And if your house is two full floors rather than one and a bit, read Wi-Fi for a two-story house as well — the layout advice there is more specific than this page can be.