I have a house awaiting settlement so I can't exactly back out! Anyway, the house has a paved patio at the back held by a retaining wall at the end as the property slopes downward in the backyard. When I first inspected the property I noticed that the patio wasn't level at the far end and thought I could just fix that myself later on. Many weeks later after doing another inspection I noticed that the retaining wall is bulging out and may actually give in at some point in the future.
From the looks of it, the wall wasn't properly designed to hold the patio, which held several outdoor furniture and presumably a lot of people during parties, etc. It seems that the wall was originally built to hold a garden and the previous owners decided to pave it with bricks without upgrading the wall. It is quite possible that it doesn't even have any mortar holding it together all.
Long story short I think I will need to rebuild the wall myself but need advice on materials to use. I plan to put a pergola over this patio in the next couple of years so I'll eventually be putting stuff in there that will put a lot of pressure on the wall. What are the general guidelines for building a patio retaining wall for maximum longevity? What sort of bricks and mortar should I use?
Also, are there other things I need to look out for when rebuilding retaining walls?