Crawl space support posts (also called piers) are vertical columns – generally made of steel, wood, or concrete – that support houses with crawl spaces. Crawl space support posts hold up the girders (also called beams), and the girders hold up the floor joists. The crawl space support posts are installed vertically, perpendicular to the ground, and strategically located throughout the crawl space area. The entire structure supports the weight of the main floor. However, crawl space support posts can weaken over time for various reasons.