Water leaking into a basement after heavy rain is a common issue caused by multiple factors. Heavy rainfall can overwhelm drainage systems, leading to water pooling around the foundation. Cracked or damaged foundation walls allow water to seep through, while poor drainage can create a buildup of water pressure against the foundation. Addressing these problems requires a comprehensive approach, including exterior waterproofing to seal the foundation walls and slabs, improving drainage to divert water away from the house, and repairing any cracks or damage to the foundation to prevent further water intrusion.