If the downspout is too short water will not drain properly away from the home. This will collect next to the foundation wall, seep under the foundation causing the foundation to crack and transfer these stress movements throughout the house. Some evidence of these cracks are found near the corners of the house in a form of steps going up diagonally. Under window wells. When doors and windows do not open smoothly it could be evidence of structural damage. Just buy some extensions for your downspouts and protect your large investment.