Good Ways to Reinforce a Floor

Building Code Requirements

• For safety purposes, states impose certain building code requirements for new home constructions and renovations. When building a flooring system, building codes list the types of floor supports that must be in place. For example, building codes specify that joists, or floor supports, must sit anywhere from 12 to 16 inches apart for areas of up to 20 square feet. While these requirements provide a certain measure of safety, these safety measures have more to do with preventing plaster ceilings from cracking than they do with constructing non-bending flooring.

Two-by-Fours

• Over time, sub-flooring materials may begin to weaken, causing the floor to bend or become springy. Reinforcing the underside involves placing 2-by-4's alongside the joists. The two-by-fours should be the same length as the joist supports. Securing them in place involves using adhesives and nails to bond 2-by-4's to joist pieces. This method works well in cases where plumbing pipes or wiring lay between joist sections, though joist edges must remain clear of any wires, pipes or ductwork.

Joist Doubling

• Joist doubling—also known as “sistering”—aligns sister joists alongside existing ones. In effect, doubling-up joist supports provides added strength and durability by increasing the thickness of each joist support. Sister joists have the same length and width as the existing supports. Another “sistering” method involves using a flitch beam, which bolts onto an old joist using a steel plate. With both approaches, areas between joist supports must be free of any ductwork, wiring or plumbing fixtures.

Beams & Columns

• When floorboards bounce in response to walking or moving about, floor joists flex with the added weight and movement. Inserting beams and installing columns provides the added support needed to counteract joist flexing. This method involves positioning beams at perpendicular angles, so they branch out from the center of each joist. The beams provide an overhead framework for placing columns underneath. In effect, the columns stand inside the bottom floor room and support the beams from underneath, so they take up area within a room underneath. The combined support from beams and columns provides the most effective method for preventing floors from sagging or bouncing.