Hey folks, I'm Andy, co-founder of BEEST, and my family makes spray foam for people who fix their own houses.

Every November the same calls come in.

“My kitchen floor is freezing. I turned the heat up. I put rugs down. Nothing works.”

So I'm going to tell you what I tell every one of them.

Your floors aren't cold because your furnace is weak. They're cold because of a strip of bare wood you've never looked at.

It's called the rim joist. And it's the leakiest seam in your whole house.

Give me five minutes. I'll show you where it is, why nobody fixed it, and how one kit and one Saturday takes care of it.

Why Everything You've Tried Hasn't Worked

If your floors are cold, I'd bet you've tried most of this:

• Turned the thermostat up. The bill went up. The floor stayed cold.
• Put down rugs and wore slippers. Covers it up. Doesn't fix it.
• Ran a space heater in the kitchen. Treats the symptom. All day, every day.
• Pushed batts into the basement ceiling. Batts slow heat. They don't stop moving air.
• Caulked the windows. Good idea. Wrong spot.

None of it worked. And here's the part nobody told you: none of it touches the root cause.

The Hidden Root Cause: Your House Breathes Like a Chimney

Here's what's happening under your feet.

Warm air rises. It leaks out the top of your house, through the attic hatch and every gap in the ceiling.

That air has to be replaced. So the house pulls cold air in at the bottom.

Where does it get in? The rim joist. That's the band of wood sitting on top of your foundation, all the way around the house.

Go down to the basement and look up at the edge. You'll see it. Bare wood, 8 to 12 inches tall. Gaps where it meets the foundation. Gaps where every floor joist lands.

Cold air pours through those gaps all winter. It runs across the basement ceiling. Right under your kitchen floor.

That's why your floors are cold. Not the furnace. Not the windows. The rim joist.

Why Nobody Told You This

I'm not going to tell you contractors are crooks. They're not.

But a foam crew has a truck, a rig, payroll and insurance. They need jobs worth the drive.

A rim joist is about 128 square feet. That's one kit of foam. Most crews won't come out for a job that small. The ones who do price it like a big one. We've seen rim joist quotes of $1,200.

The hardware store won't tell you either. The cans on the shelf are made for a door frame, not 160 feet of rim joist. You'd empty one before you finished the first corner.

So most people never fix it. They live with cold floors and a bill that climbs every winter.

The Fix Is Simpler Than Anyone Let On

The gap and the bare wood are one problem. So the fix has to do two jobs at once.

Seal the gap. Insulate the wood. In one pass.

That's what spray foam does. It expands into the crack where the air comes in, then it sets into a layer of insulation on the joist.

And that's why we built FullStop as a 12-can kit with a real metal gun, not a single can.

• 12 cans and a metal gun. Enough foam for a typical rim joist at 1 inch. No compressor. No rental.
• R-4.12 per inch. Two 1-inch passes get you R-8.24 at 2 inches.
• DualCore foam. A closed-cell outer skin with a flexible center. People ask us open or closed cell. It's a blend of both.
• Class A fire-rated. Cured FullStop tested ASTM E84 with a Flame Spread Index of 0.* Your local code still decides whether it needs an ignition or thermal barrier, so check with your inspector.
• Gloves, goggles and a coverall in the box. Plus a metal gun and cleaner. Bring your own respirator.

How One Saturday Goes

Here's the job, start to finish.

1. Warm the cans to 68F. Leave them in the kitchen overnight. The basement surface and air need to be 41F or warmer.
2. Check that it's dry. Never spray a wet surface. Damp basement? Put poly sheeting on the wall first.
3. Suit up. Respirator, gloves, goggles, coverall. Every time.
4. Practice on cardboard. Five minutes with the gun and you've got it.
5. Spray each joist bay in a 1-inch pass. Hit the seam at the foundation and the seam at the joist first. Let it set. Come back for a second pass if you want 2 inches.
6. Air it out. Keep the basement ventilated. Give it 24 to 72 hours before you spend time down there.

Keep flames, sparks and pilot lights away while you spray and until the vapors clear. In tight bays, the extension tube on the gun helps.

How Many Kits Does a Rim Joist Take?

This is the first question everyone asks. Here's the honest math.

One kit is 12 cans, rated 240 sq ft at 1 inch on paper. Real use runs about 70% of that. That's our estimate, not a lab test.

A typical rim joist runs about 160 feet around the house and 10 inches tall. About 128 sq ft.

Real use, rounded up. Overhead work uses more.

Round up, never down. One buyer put it best: “Covers less than you think it will, plan ahead.”

Bigger house, or doing the crawl space walls too? Use the calculator.

Use the calculator →

What Happened in Other People's Basements

“I used this to fill in the sill plate voids in the basement between the floor joists and the outside wall.”

“Surprised how easy this was. I had never used spray foam before this but it really was pretty simple after about 5 minutes.”

“Used in crawlspace area. Extremely easy to use even when cramped on your belly.”

“Was nice to be able to speak with someone.”

FullStop customer reviews, Judge.me. Verbatim.

We asked our customers what changed after the job:

Customer-reported, individual experiences vary. Not a promise of savings from BEEST.

The Questions I Get Before People Buy

Will it trap moisture and rot my joists?

FullStop is a vapor resister, not a vapor barrier. In a damp basement, put up poly sheeting first. Never spray wet wood.

Is it flammable?

While you spray and before it cures, yes. Keep flames, sparks and pilot lights away until the vapors clear. Cured FullStop is Class A fire-rated (ASTM E84), Flame Spread Index 0.* Your local code decides whether it needs an ignition or thermal barrier.

Can I spray upside down into the sill plate?

Tight, overhead bays are the normal job for this kit. Ask us about inverted spraying before you order and we'll set you up.

I've never sprayed foam. Can I do this?

Plenty of our buyers had never touched foam before. Practice on cardboard, spray thin passes, let each one set, and you'll be fine.

Isn't it cheaper somewhere else?

The kit comes with a metal gun, cleaner, gloves, goggles, a coverall and video help. And a person who picks up the phone when you have a question halfway through the job.

Is this a real company?

We're BEEST, a family-owned company. Call us before you order and a real person answers: 1 (800) 540-4671.

Here's What I'd Do This Weekend

Go down to your basement tonight. Look up at the edge. Feel for the draft.

Then do it before the cold really sets in. FullStop needs 41F or warmer, surface and air. In most of the country that window is closing.