How to Reinforce Floor Joists for Plumbing: 4 Easy Steps

A joist hole reinforcer is a straightforward product that allows you to reinforce a floor joist that actually has plumbing running through it. While there are several brands of these plates, and some of them even come as kits, they all generally work the same way. 

Joist reinforcement plates come in standard sizes, usually including 2” x 8”, 2” x 10”, and 2” x “12”. To strengthen the joists: 

  • Prepare the area for installation.
  • Position the plate at least one foot from the bearing point.
  • Fix it with a clamp to hold it firm.
  • Fasten it in place, using the included fasteners.

How to Use a Joist Reinforcement Plate

Joist reinforcement plates let you strengthen the joists with steel supports, so you can fix any damage or strengthen holes and notches to meet the plumbing code.

Things You’ll Need

  • Cordless or Corded Drill
  • Socket or Nut Driver
  • Construction Adhesive
  • Floor Joist Repair Kit (includes: fasteners, driver, and instructions)
  • “C” Clamps (optional)

1. Prepare The Area For Installation

Gather everything that you will need to install the joist reinforcement plates. 

Your kit should include two plates, an eighth-inch drill bit, a Robertson screw tip, all of the fasteners needed to attach the plates to the joist, and installation instructions. 

Unpack these items and add them to your drill, socket, driver, and construction adhesive. 

2. Placement of the Joist Reinforcement Plate

The center of the hole that you are reinforcing must be at least one foot or 12 inches from a bearing point. This includes places like walls or columns, where weight is concentrated and can be redistributed to the foundation. 

You may only legally use one hole reinforcer per joist. However, you may use them in as many joists as you like, allowing you to run drain pipes and utilities through multiple beams. 

3. Fix The Plates In Place

Line up the plates so that they match with the edges and center of the hole. You will be placing one plate on each side. 

When you are sure of the alignment that you want, use the construction adhesive to attach the plates. 

You can also use the “C” clamps to make sure that the plates are held in place while you are screwing them in. 

4. Attach Floor Joist Reinforcement Plates

Attach floor joist reinforcement plates using the fasteners included. You will need your drill for this. 

Once the plates are glued and screwed into place, the job is finished and you can rest assured that your floor joists are secure, even with plumbing running through them. 


Other Methods for Strengthening Floor Joists for Plumbing

Floor joist reinforcement plates, also called plating, are often used when a drainpipe runs through the floor joists. 

While this is sometimes necessary there are many times that floor joists need to be repaired because of damage due to plumbing or because of a need to bear extraordinary weight such as that imposed by large bathroom appliances and fixtures. 

There are many types of plumbing that require floor joists. One of the most popular home improvements right now is a bathroom remodel. 

From adding a spectacular clawfoot bathtub to installing a new shower, reinforced floor joists are likely to be needed. 

Scabbing

The simplest way to reinforce floor joists is with the scabbing method. 

Things You’ll Need:

  • Lumber or Plywood (appropriately sized)
  • Nails
  • Nail Gun or Hammer

1. Place Lumber Over Area of Concern

Place the piece of lumber over the exact area that is of concern. It is very important that the piece of lumber covers the entire area of concern and at least a few inches beyond.

2. Attach the Lumber to the Floor Joist

Using either the hammer or the nail gun, nail the lumber directly to the floor beam. If extra security is needed, you may add lumber to both sides of the joist. 

Scabbing works best to handle a small problem. There are many other methods for reinforcing food joists for plumbing. This guide will teach you about other methods that can be used in more specific situations. 

Sistering

Sistering is a process that is very similar to scabbing, but the pieces used for reinforcement are significantly longer and usually found on both sides of a joist. It is also important that the pieces of lumber used for the sistering are the same type and width as the joist.

Things You’ll Need:

  • Bricks
  • Wood Clamp
  • Lumber for Repairs
  • Bolts
  • Corded or Cordless Drill
  • Nail Gun or Hammer
  • Nails

1. Prepare the Area

Place bricks underneath the joist for extra support during your work. Use a wood clamp to hold the pieces being sistered to the joist in place.

2. Attach the Sistering Pieces

Attach the Sistering Pieces to the joist directly with nails. Drill holes appropriately for the bolts. Bolt the sistering pieces to the joist to secure them permanently.

3. Finish Up

Remove the wood clamps. Remove the bricks. The sistering pieces should be firmly in place and provide extra support and the job is finished. 

Blocking

Blocking does not run parallel to floor joists like scabbing or sistering does. With blocking the supports run perpendicular in between the joists. 

Things You’ll Need:

  • Lumber for repairs
  • Nail gun or hammer
  • Nails

1. Place the Lumber Supports

Using appropriately sized pieces of lumber or plywood, fit the blocking piece between the floor joists needing support. It should be at a 90-degree angle to both floor joists. 

2. Attach the Lumber Supports to the Joists

Using a nail gun or hammer, nail each side of the block piece to the joist. 

Bridging

Bridging runs perpendicular to floor jousting like blocking does. However, two supporting pieces are used to create a crisscross pattern. 

The method for attaching them is slightly different depending on the material you use. This is most often done using metal which can simply be nailed into the wooden floor joist.

Things You’ll Need:

  • Metal Bridging Pieces
  • Nail Gun or Hammer
  • Nails

1. Decide on Bridge Placement

Divide your floor area that needs reinforcement by three. You will want to place a bridge at every third interval. 

2. Nail Metal Reinforcement Pieces

Nail the notches of the strengthening pieces directly to the floor joists. Nail each end to opposite joists to create a crisscross pattern


To End

Having strong bathroom and kitchen floors is fundamental to a sound home. Reinforcing the floor joists with metal plates is easy. Simply decide where to place the plate, drill a hole, and fix it with the fasteners included in the pack. Otherwise, you can use any of the alternative methods above.