Elevation Options for Non-Slab Houses

Jack Elevation

Jahn’s Unified 16 Jack System

Lifts the entire house with floor attached and builds new piers or a foundation wall Steel Beams are placed under the floor framing. Next, the house is raised in small increments with hydraulic jacks. “Cribbing” (normally stacked oak beams) is placed beneath the steel beams to provide a support for the hydraulic jacks and a safety backup to prevent a catastrophic collapse of the house. This process is repeated until the desired height is reached. When the required elevation is reached, the original foundation piers are removed and a trench is dug around the perimeter of the house and at other locations where a foundation system (piers) will be required. Next, rebar (steel reinforcing) is laid in the trench, and cement is poured in the trenches of the foundation system to form a (steel-reinforced) chain wall. Finally, new piers are built below the raised house. Foundation walls can be constructed below the living space, with vents/openings for the entry and exit of future flood waters, to create a new underhouse garage or storage area (non-habitable space). This technique is generally considered the most cost-effective for houses that are already partially raised or already restored after having been damaged, although repairing already restored interior walls is not covered under HMGP funding.

Jahn’s Unified 16 Jack System

Although jack elevation is the most widely used elevation technique for non-slab houses, other techniques exist:

• Second Story Add-on and Wall Extension. The Second Story Add-On technique converts the existing first floor of the house to “non-habitable” space and builds a new second story living area. (This is often called a “raised basement” house).
• The Wall Extension technique extends the existing walls of the house upward and raises the lowest floor.

With both techniques, an engineer should be consulted to determine if the existing foundation can support the additional loads imposed. A new foundation system may be required. These techniques are only appropriate for masonry houses.

Elevation Options for Slab Houses

Slab Separation

Lifts the house by detaching the entire structure from the slab foundation. Exterior siding must be removed, but may, in some cases, be reinstalled later. The house is braced, and beams are placed through the house to support it as it is raised (which means interior walls must be redone). Next, the house is raised in small increments with hydraulic jacks.

Slab Separation Lowered on New Subfloor

“Cribbing” (normally stacked oak beams) is placed beneath the steel beams to provide a support for the hydraulic jacks and a safety backup to prevent a catastrophic collapse of the house. This process is repeated until the desired elevation height is reached. Piers are constructed for support on top of the existing slab.

Foundation walls, which add extra support to the elevated structure, can be constructed, with vents/ openings for the entry and exit of future flood waters, to create a new under-house garage or storage area (non-habitable space).

Slab Elevation

Lifts the entire house with slab floor attached,  and places it on a new foundation higher off the ground. First, trenches are  dug immediately below the slab to expose the slab footing. Then, tunnels are  dug under the slab to allow for the insertion of steel beams. If pilings are  present beneath the slab (common in Metro New Orleans) the pilings will be  detached from the slab. Next, the house is raised in small increments with  hydraulic jacks. "Cribbing" (normally stacked oak beams) is placed  beneath the steel beams to provide support for the hydraulic jacks and a safety  backup to prevent a catastrophic collapse of the house.

This process is  repeated until the desired elevation height is reached. Next, rebar (steel  reinforcing) is laid in trenches around the perimeter of the house and other  necessary areas, and cement is poured in the trenches of the foundation system  to form a (steel-reinforced) chain wall. Finally, a new foundation wall is  built below the raised slab with vents/openings for the entry and exit of  floodwaters.

This technique is generally considered the most costeffective for houses that are already restored, although repairing restored walls may not be covered under the current public funding options available. Plumbing repair is potentially more difficult with this option than with others. The slab elevation method is relatively new to the New Orleans area, so long-term stability of structures elevated with this technique has yet to be proven.

Second Story Add-On

Second story add-on

Converts the existing lower area of the house to “non-habitable” space and builds a new second story living area. (This is often called a “raised basement” house.) The roof is removed and the framing for the second story is constructed . On the ground floor, vents/openings are required to be added to allow the entry and exit of future flood waters. Electric and plumbing outlets are not allowed by code . Next, the original or rebuilt roof is installed with hurricane straps and the second story siding is added. Finally, the lower floor is converted into a non-habitable space for storage, parking, and/or building access. The lower floor must meet the FEMA guidelines and will not be insurable by the National Flood Insurance Program as living space. An engineer should be consulted to determine if the existing foundation can support the additional loads imposed. A new foundation system may be required.

Wall Extension

Extends the existing walls of the house upward and raises the lowest floor.  In this option, the roof is removed and the structural framing members supporting the roof are extended upward (less than one-story). New bricks or other siding material are then added to complete the exterior renovation. Then, a new wood frame lowest floor is constructed above the original one and above the flood level with vents/openings underneath to allow entry and exit of future floodwaters. Finally, the roof is re-installed with hurricane straps and all necessary structural modifications, to meet the new wind code. An engineer should be consulted to determine if the existing foundation can support the additional loads imposed. A new foundation system may be required.
*These techniques are appropriate for masonry houses.

Generally, non-slab-elevation is less expensive than elevating a slab home. The following list of factors typically affect the cost of elevating a house:

1. Size– The larger the house, the higher the cost.
2. Siding– Generally, houses with brick veneer cost more to e.Jevate than those with wood siding or stucco. For jack elevations, interior and exterior wall damage may result, although the brick wall may survive. The wall extension option is a way of retaining brick veneer, by adding more bricks.
3. Chimney– Fragile masonry requires extra time to dismantle and/or brace during elevation. Non-masonry chimneys would not add significant cost to the project.
4. Interior– The inside walls of homes (sheetrock, plaster, etc.) may be damaged by any method of elevation
5. Proximity to Other Structures – The greater the distance between the house and adjacent structures, the easier it is for contractors to move equipment on and off of the site, which is reflected in the cost.
6. Height of House Elevation – Higher elevation results in more expense for materials/labor. In addition, engineering concerns become more critical as the height of elevation increases, given the added potential vulnerability of the structure to high winds. Second engineering opinions are particularly worthwhile in cases involving significant elevation.
7. Additions– Existing additions tend to increase the complexity of the elevation job, and thus the cost.
8. Utilities– Must be brought up to code after your home is elevated. This should be considered in your total cost.