Wi-Fi won't travel through your house? It might be the wire in the walls

Older houses that mysteriously refuse to let Wi-Fi signals pass through their walls might have a hidden ingredient: wire in the walls that kills the signal

If you add wire like this, it makes the plaster stick better, but kills your Wi-Fi. Choices, choices... / Photo by Gnomedude on Flickr / CC BY licensed

Got an old house? Got Wi-Fi? Discovered you can't get the Wi-Fi signal to travel anywhere in the house, so that you have to resort to HomePlugs to send the signal via the mains? Then you've got plenty in common with people in San Francisco and other parts of the US who have just the same problem.

The culprit? Plaster-and-lath walls - specifically when the lath (or base structure) of the wall is chicken wire or similar corrugated wire, to which the plaster is added to create the wall. Such walls are sometimes internal, often external, but always death to Wi-Fi signals because the wire acts as a Faraday cage, killing the signal.

Hence a long and interesting piece at the Wall Street Journal - entitled Culprit in Wi-Fi Failure: Chicken Wire - which looks at the problem, particularly in San Francisco, where the combination of desire to use Wi-Fi and wire lath is particularly high. Plasterboard (which Americans call "drywall"), which doesn't have wire components, doesn't block it to anything like the same extent.

Mr. Pewtherer's 80-year-old building in the Mission District, like thousands of other old homes in the Bay Area, was built with the technological equivalent of kryptonite in its walls: chicken wire. Metal wiring inside old plaster walls blocks wireless signals, frustrating San Francisco residents as wireless-equipped devices like iPhones and laptops proliferate.


Often, lath in Victorian and Edwardian-era homes was made of wood stapled with chicken wire, a cheap fencing material that also doubles as lightweight support. The problem occurs in other cities too, but San Francisco has an unusually dense collection of old homes and gadget lovers.

"It's the old bumping into the new," says Mike Scott, a technical media manager for network gear maker D-Link Corp., who fields many questions about chicken wire. "How were people 70 years ago supposed to know that we were going to have all of these wireless gadgets?"

(By the same token, our present eagerness for double glazing is sure to frustrate all the people using zero-point energy beamed down from space to heat and light their homes in 2100.)

There's a paper with measurements of the comparative absorption at 2.4GHz of various building materials (PDF). If you have a look at figure 32 on p20, you'll see that wire-based lath has almost perfect absorption at 2.4GHz - the Wi-Fi frequency. Which is not what you want.

So is that an "aha" moment for you (as it is for me, realising why the room built outside the wire-and-plaster lath wall doesn't get any Wi-Fi)? Though, of course, it gives those worried about Wi-Fi a place to run to...