This could occur for a variety of reasons. Age of home? Drainage installed at the base of the footing of the home or business? Basic waterproofing installed at the time of home or business construction? What happens is that over time the block or concrete construction at the footer can cause a "Cold Joint" which allows water to find its way in. Water will travel the path of least resistance and find its way in at these cold joints. Concrete will expand and contract during the thaw and freeze cycle of the seasons contributing to the movement of the concrete and joints. All basements are built on a foundation and a slab that is poured into the footer. As time goes on this slab will shrink and pull away from the foundation. We may be only talking about a 1/4" but enough to allow water to come through the cold joint as the water builds pressure in a heavy rain thus pushing its way in at the base. Another issue is the normal shifting, movement, and settling of your home or business foundation. This is somewhat normal but can be expedited egregiously by standing water. It is imperative to keep standing water away from the perimeter of your home or business. Newer homes with monolithic concrete poured foundation walls are typically more sound but can crack and if they do water can come in through that crack.
The solutions vary. You can traditionally dig out the perimeter of your home or business, clean and wrap the foundation with a quality vinyl membrane, and add a french drain to the base of the footing. You can install a drain system within the inside of the basement by trenching the entire interior perimeter of the basement, add a sump pump system, and repour concrete over the trench or you can opt for a much less invasive option and have the problem areas treated by way of polyurethane injection. The first two methods are very intrusive and are heavy construction. In most cases for the exterior waterproofing option, the HVAC system must be disconnected for several days and reconnected. Your property will be for a lack of a better word, destroyed due to a great deal of dirt from the perimeter and heavy equipment and both those options are very expensive. The polyurethane treatment method is permanent, non-corrosive, typically less costly, and non-invasive and can usually be completed in one or two days depending on the size of the perimeter of the home.
Absolutely! Once all leaks have been stopped you should not have any issues. The only thing that can disrupt the repair and sealing is if some form of construction has been completed and it affects the sealing of the joints. Another potential issue but not a likely one is the major shifting of the foundation causing the joint to pull away from the bonding of the polyurethane.
Efflorescence. Efflorescence is the result of minerals dissolving as water evaporates on porous material such as basement concrete or block walls and or floors. The deposits are NOT harmful but a clear indication that moisture and or water penetration is present in your home or business.
Yes. By way of polyurethane foam injection at the base or walls or by a drainage system installed at the base only and only addresses the base/footing.
This can be tricky but typically yes with limitations being time and other circumstances as outlined previously in this Q and A. The time of warranty can vary.