Clay blocks were not fired long enough to have a hardened surface like brick, so they are vulnerable to the destructive effects of weather exposure. If the outside foundation walls become open to the elements, the blocks can become soft and porous, and will spall or deteriorate in a fairly short period of time. This can lead to voids in your foundation and water seeping into your basement. It’s important that you fill any voids where the block face may have broken away. Use some old bricks and mortar to fill the opening. You can use the same method to make a repair on the interior surface of the wall.
If your lawn has settled over the years, exposing the clay blocks, it is to your advantage to get it covered back up again as soon as possible. There are several ways to go about this. The easiest approach is to ‘ramp’ soil around the house so that the exposed blocks of your foundation are covered, sloping away from the house to the level of the rest of the lawn. The ramped soil will also direct surface water away from the foundation preventing water seepage into the wall. Another way would be to bring in a couple of loads of topsoil to raise the level of the lawn around the house to cover the clay tile. Then, you would have to plant new grass seed. This method involves a lot of labor—your own or paid help—and patience in tending the new grass. A third method would be to take some railroad ties or treated landscape timbers and enclose an area surrounding the foundation. The enclosed area, when filled with dirt high enough to cover the exposed blocks, will give you a raised bed perfect for planting shrubs or flowers. Keep shrubs a couple of feet or more away from the house.
There are some other simple ways of doing all this—but, however you do it, the object is to get the tile covered and protected from the weather. Like many smaller repairs, this situation has a way of turning into a bigger problem, if care is not taken. So, take a look around your home, see what is your situation, and plan your course of action.