Wi-Fi weak upstairs: why floors block more than walls

It's one of the most common complaints in two-story homes: the router is on the ground floor, the bedrooms are upstairs, and the signal that easily crosses two walls downstairs barely makes it through the ceiling.

Why a floor is worse than a wall

It's thicker and denser. An internal wall is often plasterboard or light brick. A floor is joists, boards, insulation and, in many homes, a concrete slab with steel mesh inside. Add underfloor heating pipes or a foil-backed insulation layer and the floor becomes a screen.

The angle is worse. A router in a downstairs corner reaches the upstairs bedroom on the opposite side at a shallow angle. At a shallow angle the signal travels through much more floor than the floor's actual thickness.

Router antennas favor sideways. Most routers use antennas that radiate like a flattened doughnut: strong outward, weak straight up and down. A router with every antenna pointing up sends the least signal exactly where the floor above is.

The free fixes first

• Raise the router. On a high shelf or on top of a tall cabinet, the router is closer to the ceiling and has a better angle upward.
• Move it toward the middle of the house, ideally under the upstairs rooms you use most, not in a far corner.
• Use the stairwell. A router near the stairs sends a lot of signal up the open space instead of through the slab.
• Tilt one antenna. If the router has external antennas, lay one or two of them at an angle or horizontal. That shifts some of the coverage from sideways to vertical. Try it and measure; the result depends on the router.
• Get it out of the cabinet. A router tucked low inside furniture loses a lot upward.

When the free fixes aren't enough

• One node at the top of the stairs. For a mesh system or extender, the landing is usually the best spot: it still hears the router well through the stairwell and covers the rooms around it. See where to put a mesh node.
• A wired access point upstairs. If you can bring an Ethernet cable up, an access point or wired mesh node upstairs gives the whole floor full-strength Wi-Fi. Many homes have a cable route next to pipes or in a cupboard.
• Upgrade the router only if it's old. A newer router doesn't pass through concrete better. Moving or adding one works; replacing one in the same spot rarely does.

For the bigger picture, see how many mesh nodes you need.

Measure both floors, not just the bad room

Upstairs problems are rarely one room. A map of both floors shows whether the whole upper floor is weak (the floor is the problem) or just the far corner (distance is). WiFi Heatmap lets you map each floor separately on your iPhone, move the router or the node, and compare the new map with the old one.