What is the difference between a rim joist and a band joist?

They are the same thing — the term varies by region. Both refer to the perimeter joist that caps the ends of the floor joists.

Should rim joists be insulated?

Yes. Rim joists account for up to 15% of heat loss in many homes. Rigid foam cut-to-fit and caulked is the most effective method.

Rim Joist Calculator

Calculate the number of rim joist boards needed for your floor framing perimeter.

Ad — 728x90 — Leaderboard

Enter Your Measurements

Ad — 336x280 — Rectangle

How to Use This Calculator

1Measure your floor frame perimeter in feet.
2Enter the board length you'll be using.
3Click Calculate for your rim joist count.

Ad — 728x90 — Mid-Page

About This Material

Rim joists (also called band joists) run along the perimeter of the floor frame, capping the ends of the floor joists. They are typically the same dimension as the floor joists (2x8, 2x10, 2x12).

Installation Tips

•Install rim joists flush with the top of floor joists.
•Nail through the rim joist into each floor joist end.
•Consider insulating rim joists — they are a significant heat loss area.

Common Mistakes to Avoid

Not blocking or insulating the rim joist cavity in conditioned spaces.
Using the wrong lumber dimension — match your floor joist depth.