I would, if had an easy way to do it, put a booster just inside the wall nearest your deck or patio. A hard link (wired) from a router to an access point might be best. And no pringles can, just use the reject rate to tell you when you need a booster-- I use 25% loss as a good basic boundary as the loss is not straight line.

One class of things: electrical lines and metal pipes and metal heating ducts can dampen signals like you would not believe and also flourescent fixtures with ballasts in them (these last gen a radical FM interference and an AM interference field, as the hardware store chain I worked for found out-- folks had to be told they could bring clock radios back if they were not happier at home than with the demos as we could only get the closest stations inside the store (at home, with many fewer flourescent fixtures) those GEs worked like champs.

So, if feasible, the wireless gear should also be away from a flourescent fixture of older kind for much better range. The Pringles can cobbled induction coil antenna booster might be used at the WAP or wireless router end, instead, and help extend range also. Even mounting the router on a shelf close to lower level's ceiling should help a tib.

Red brick does not dampen as badly as metal, for the wavelengths we are talking about, either. Adn keep your wireless WAP or router 10-15 feet away from computer area if you have things in a corner, the computer gear in nice metal cases and generating fields itself can mess with signals.

A shielded (STP or Plenum) wire to computer gear from router or WAP will not act as much as an EFI antenna either. Shielding enhances both signal retention (less loss) AND erroneous field or signal noise exclusion-- in the latter case it keeps the signal from hitting the inner conductors better than unshielded cable.