Remodeling
Success 101

Q: How do you excavate for a full, livable basement under an existing house?

A: First, a convenient location along the home’s perimeter is located to serve as the access point. Using a small excavator (e.g., a Bobcat), a sloping dirt driveway is excavated to the depth of the new basement foundation at the chosen location. Then dirt underneath the house is removed until the area is excavated according to the approved building plans and design. Along the way, the existing foundation and structural frame will be shored up until the structural elements of the new basement are complete.

If you've ever driven past a new subdivision just getting started, you've likely seen a fleet of earth-moving equipment, multiple colored stakes in the ground, and the beginnings of streets, sidewalks, and foundations. These are the tell-tale signs of the building site being prepared for construction.

While it's true that remodeling is a vastly different building process than new construction, there are often similar steps a professional contractor must take to prepare a site for a remodeling project. That's especially true if new space will be added, whether it is adjacent to the existing house, above it as a second level, or underneath it as a livable basement.

Simply put, whenever a remodeling job calls for some change in the home's structure, remodelers are usually required to check and confirm a variety of site conditions before construction begins.

Site preparation includes several steps. A survey comes first. Topographical features -- trees, streams, rocky outcroppings, relative elevations, and open areas -- must be accurately located when space is to be added. Property lines must be located precisely to confirm setbacks (the allowable distance between a structure and a property line) in compliance with local codes. Then the surveyors stake out the location of the various underground utility conduits so that the remodeler can assess their capacity to serve the new space and house. A soils test should be made to help determine the type and design of the foundation construction. Finally, the builder makes an assessment of the home's existing structural integrity to make sure it is adequate to carry the weight (or load) of the addition.

Most, if not all, of these tests and studies are mandated by the local building authority. When plans and construction drawings are submitted for permits or approvals by that authority, the tests and studies must be attached, usually signed and stamped by a registered professional engineer.

Once those steps are taken and the plans are approved by the building department, the remodeling contractor may take a few more "site prep" steps before beginning an addition. The location of the foundation or footprint of the new addition is staked to provide a guide for excavation. Typically, the stakes and batter boards (which demarcate every corner or turn in the layout) are connected by nylon strings to outline the exact perimeter of the foundation to be built.

The last steps of site preparation take place when the backhoe or excavator arrives. Ditches are dug to extend existing or new utility conduits -- for electrical, plumbing, natural gas, etc. -- to serve the new room. Finally, foundations are excavated using the staked-out lines as a guide. Plans for new space will call for footings and -- according to individual designs -- a crawl space, full basement, concrete slab, and/or perimeter foundation walls in preparation for concrete forms, blocks, or other materials to support the main floor.

For a second-story addition, of course, there's no need (or opportunity) to stake out the perimeter. Nevertheless, to guide both demolition and framing crews, marks are made to identify the sections of the existing structural members, such as the roof trusses, that will be cut away to make room for the new space above.

Similarly, "excavation" for a second-story addition involves shoring or temporarily supporting the existing structure while other sections are demolished and removed in preparation for framing the new section. In other words, the existing structural members are 'excavated' in preparation for new construction.

To be sure, not all remodeling projects require these steps. A particular project may not require any semblance of site preparation in the classic definition of the term. Because it is so often necessary, however, it is important for our clients to understand this phase and prepare for a week or so of noise, dust, and demolition mess. Site preparation is soon forgotten as the client's vision for a renewed home takes three-dimensional form.

Warm regards,

info@highcraft.net
www.highcraft.net

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