Most residential foundations in the Northeast are deep, with full basements. As a result, details for slab-on-grade foundations are less commonly known. Many builders simply apply the same details used in more southerly climates, where slabs are more prevalent. This isn't ideal, particularly now that energy concerns have led to the use of more insulation. Foundation details need to take into account the added insulation. This article is based on principles discussed in the Builders Foundation Design Handbook (University of Minnesota Underground Space Center, 500 Pillsbury Drive SE, Minneapolis, MN 55455, 349 pages; $33). Insulation: Where and How Much? Insulation may be located either inside or outside the foundation wall, and it may be positioned either vertically or horizontally. Insulated concrete masonry can