Home Elevator Construction
An elevator project consists of far more than an elevator. Think of it like a complex kitchen remodel. There is far more to it than kitchen cabinets. The fact of the matter is that before an elevator can be installed, structural surgery to your home has to take place. The holes or elevator shaft going from floor to floor involves cutting joists the bones of your home to make a proper hole on each floor. This may be a simple matter.
There are generally two approaches inside of your home, elevator shaft or through the floor elevator no shaft, sometimes called shaftless elevator.
Through the Floor Shaftless Elevator Projects
No shaft “holes only” involves cutting back the joists in the proposed location of the elevator and then supporting the cut joists with headers and then supporting the headers on LVL beams sister-ed to the joists which are outside of the proposed hole. Doubling joists is generally considered to making a beam. These new beams, like the joists they are sister-ed to, must run from load transfer to load transfer points. Load transfer points are the front and rear walls of your house and the steel beam which runs through the middle of your home.
An excellent example of this is your basement stairwell. Your basement steps are in a hole in the floor. Often the top of those steps are loaded right on top of the steel beam running through the center of the house. On each side of the stair-case the joists are doubled creating beams. These two beams run from the steel beam to the front wall of your house. Above the bottom of the steps you can see the header which is carrying the load of the one or two joists which had to be cut to make the stair way hole. The header distributes the weight of those cut joists to the beams and the beams transfer their weight along with other weight to the steel beam and the front wall of the house.
To complicate matters there is often infrastructure such as duct, waste and supply plumbing lines, electrical lines as well as gas line and sprinkler line. This infrastructure passing through the joists usually has to come down temporarily so the LVL’s can be sister-ed to the outside joists. Once the combination becomes a beam the infrastructure may be put back in. Sometimes it cannot be put back in and has to be rerouted.
This description is relatively accurate for a house built before the mid 1990’s. New construction is often more complex. The advent of engineered framing products such as TGI’s (plywood with 2×4 top and bottom caps), LVL’s compressed wood fiber (think super thick super dense plywood) and truss floor systems can make the sistering of joist to make a beam very challenging. There are rules for engineered framing which often precludes allowing anything to pass through them or limits the size of the holes.
Elevators which might go into a No Shaft or “Hole Only” projects would be Stiltz Lifts Home Elevators, Pneumatic Vacuum Elevators and Pollack Elevators. These residential elevators generally are not pulling on the walls. All of their forces are in compression.
Shaft Elevator Projects
Most people, when thinking of home elevators, think of them in an elevator shaft. There is usually a pit and framed walls on each floor completely enclosing the elevator. The pit is built by cutting out the floor, then excavating, then building a rebar cage, inserting concrete forms, getting inspected and then pouring concrete. All of which create a very strong yet relatively small sunken floor big enough for the elevator cab. The pit allows the superstructure under the cab to descend below the basement floor for a smooth unobstructed entry and exit. No ramp is necessary.
Forces in Tension
The walls must be built in a very strong way because the elevator is hanging on one of them which we call the rail wall. This wall must withstand forces in tension, about 2,000 pounds pulling on it for the rest of time. An easy way to understand forces in tension is to think of a tree 30 or 40 feet tall. Then imagine attaching an elevator cab filled with 1000 pounds of people to the tree 30 or 40 feet above ground. The force of that weight pulling on the tree is tension. Do you think that force will pull the tree down? The answer is yes. It may happen right away or take a few days but eventually 2000 pounds in tension is going to pull the tree to the ground. How well the shaft is built and how well it is tied into the structure of the house is how it withstands the forces in tension. A structural engineer determines how this is done. We provide the engineer with a forces diagram and he determines how to tie the rail wall into the house.
Types of Elevators We Install
At Signature Elevators, we do all the construction and installation of our home elevators ourselves so we know the job is done correctly. We work with the industry’s top manufacturers to provide the highest-quality elevator systems for homes, including:
We install hydraulic, pneumatic, and traction elevators, and we can recommend the ideal solution for your home and your unique needs.
Learn which elevator is the best option for your home. Call 301-251-1658 to speak with our experts in the DC or Maryland area today.
