Water entering a slab house
First determine if it is water coming in through the "weep" holes, or it is a roof leak running down the inside of the wall. If there is a plumbing vent in this outside wall, then that could be the source of a leak.

If you determine that surface drainage is allowing water in through the weep holes, then you should regrade around the house to establish swales which drain water away from the house.

I live in a neighborhood of 50-year-old tract houses on 10,000 sq ft lots in which the original swales have pretty much filled in. Our streets run E-W and the ground slopes down to the W from a N-S ridge on the E to a creek on the W. I personally know of 3 houses which have had water ingress in recent heavy rains.

Our lot (87' wide) has an elevation change of 2.5' down from E to W. When we bought our house in 1978 the swale on the E side (our house faces N) was 90% filled in. I used a tiller to loosen the soil and reestablished the swale. It needs it again. This time I will use a mattock, a shovel and a wheelbarrow to transfer soil to the W side of our lot. We have a sunken living room, but it is on the W side (downhill). 

A year ago a neighbor had water coming into her house on the E side due to the swale being filled in. Her house has a sunken living room on the E (uphill side of her S facing house); she asked my wife to have me take a look. In 6 to 9 hr of work with a mattock, shovel and wheelbarrow in 3 sessions I was able to redirect water away from the house, and that house has stayed dry in the year since, despite heavy rains. The swales need further deepening. I did this as proof of concept, and I may do more on that drainage. The clay soil is easily workable at the correct moisture content. If dry it is like concrete.

Some people in the neighborhood have had underground "French" drains professionally installed on the uphill side. Re-establishing surface drainage is much cheaper and I believe works better.