Client has fixed up an old building and has used solid insulation which has an aluminium foil backing that acts as a heat and vapour block. It also stops WIFI dead.
Normally this wouldn’t be a problem and all your signals would be under the roof but this client has a 3-story rustic building with the office at the top and a bedroom at the back on the ground floor with a new roof. Whilst the WIFI signals are fine from the top to the bottom of the main building, immediately you pass under the foil-insulation of the extension then the signals stop.
The most cost effective solution to get WIFI to this back room without running Ethernet cables through meter thick stone walls is to use powerline adapters. Recently I have seen the retail prices for these plummet to less than 50 Euros per pair (for TP-Link brand from Amazon.it or Amazon.co.uk). Currently testing these out and they are looking fine but there is one caution that you need to consider.
These units give off a high frequency audible noise. It is like the flyback transformer of an old style CRT or TV. From experience with different customers these high frequencies can be annoying and frustrating to remove. So you may need to use powerline technology to sneak through the building and then for the last few meters use a cheap switch plus long pre-made ethernet cables or another WIFI AP.