A crack appeared in my basement wall and I wonder whether its a sign of a foundation problem. I don't have a waterproofing system in place, at least since I've moved in. What would be the best option in terms of handling this problem? I've heard of a fair amount of companies and contractors that handle this problem (like this one), but don't know of any first hand. Any advice would be welcome, thanks!

A lot depends on how big the crack is and in what direction it's running. If you have a block foundation and it's a hairline crack that mostly follows your mortar line, then there is probably not too much to worry about. However, if the gap opens by 1/16" or so or especially if the wall is bowing inwards, then it could get serious.

Small, hairline cracks are usually caused by settling. They are fairly common and rarely cause any problems unless they start growing. Inward bowing of the foundation indicates a likely tree root growing up against the house. This can be a difficult and expensive fix.

If you are unsure as to what to do, get someone with some structural experience to take look and advise you.

I didn't even think to look for hairline cracks! Thanks for your advice, I'll definitely get someone who's more experienced than I to take a look at it.

first things first regardlesws of experiance or not you can save a lot of anxiety caused by every ones ideas of what is causeing the problem first step to solving the problem is to get a shovel and dig out to the footers tapering hole to the bottom to prevent cave ins if its atree root youl find out depending on age of house could be as simple as no drainage tile and with change of seasons and amount of rainfall diferance causeing ground shift and if wall is not bowed you will need some quickcrete hydralic mix and a masonry chisel and chisel a v along the crack wider at depth than at surface makeing sure to note wether the footers are not cracked if not procede to repaire and never assume the hydraulic concrete will seal allthough more often than not it will but instead of doing all that work again get a water proof membrain tar wall with a roller apply membrane and repeat makeing sure wall has been cleaned thourly before starting seal if you have no avertion to a little hard labor you could save yourself 10 to 20 thousand dollars and the satisfaction of knowing you did it yourself. good luck whatever your deciscion .