The subject of Fire Blocking a basement seems to be surrounded by mystery and secrecy. This is an area that seems to be very confusing for a lot of DIY’ers finishing their own basement!
I know how you feel…I have been finishing basements for 27 years and in the “old days” nobody ever heard of Fire Blocking. But nowadays this has all changed…or has it?
Depending upon where you live the rules for fire blocking are quite different. I live in Pennsylvania and I can go just 10 miles in any given direction and the requirements for fire blocking a finished basement can swing 180 degrees.
It seems some areas require it…others could care less if it’s done? Hmmm? I’m not sure exactly why this is because this is an international BOCA (Building Officials and Code Administrators International) world wide requirement. Meaning, it should be required everywhere on the planet…but it’s not.
The best way to determine if you need to be fire blocking your basement exterior walls is to simply ask. I always call ahead to the permit code office and ask the code official in charge if I need to do it as part of the permit inspection process.
What does Fire-blocking a basement wall involve?
Fire blocking is a “blocking” device inserted between the top plate of your exterior wall and the Exterior masonry wall. It’s purpose is to prevent the spread of smoke and flames from reaching the bottom of the 1st floor of your home from the basement area, thereby burning through and spreading to the 1st floor of the home.
This blocking typically is made of either wood or drywall. Wood and drywall by themselves will burn so why can this be used as a fire blocking device? Well the real purpose of the blocking is to create an “air-starved” environment that will minimize the amount of combustible oxygen available and thereby starve a potential fire from spreading.
Fire blocking is required by most local building code departments when a home owner finishes their basement. Whether you hire a contractor, do it yourself, get a permit, choose not to get a permit, the truth is that installing the fire blocking is just a good idea. It might raise the overall cost of your project a little, but the peace of mind knowing that if a fire occurs in the basement wall, you and your family will have ample time to exit the house.
The block is nothing more than a 2″ x 6″ or fire-rated drywall turned flat and attached to the bottom of the first floor joists. It acts as a cap at the top of your framed basement wall to contain any fire in the wall long enough to alert the smoke alarms in the basement (see illustration at bottom). Without this blocking installed, your basement wall would actually act as a chimney and allow a fire to spread very quickly to the first floor of the house.
Most home owners finishing their basement don’t realize what this is or what it does. It can be a pain in the neck to install properly because the installer has to cut around pipes, electrical wiring, exhaust lines, etc. Any penetrations through the block have to be scaled with caulk or fire rated insulation. This means to install it correctly can be time consuming.
If you decide not to get a permit and not go through the inspections of the local building inspectors, I would still recommend installing the blocking. These two drawings below show what the framing of your basement walls would look like with and without the blocking installed:
What materials are needed to fireblock a basement?
In addition to the “blocking it’self there will be “cracks” around the blocking as well as “Holes” where wires and pipes have been installed through the top plates of the wall and through the studs in the exterior wall that will also need to be filled.
There area a lot of different code approved fire-caulks and fire expansion foams and special retardant insulation’s that you can purchase to fill these voids to pass your inspection. Some of these can be purchase at your local Home Depot. Below are a few examples:
“ALL OF THESE PRODUCTS WILL PASS CODE!”
So… I hope I have cleared up the topic of fire blocking a little bit for you. It’s an area of the basement project that stirs-up a lot of questions.
I have a quick video below where I discuss some fire blocking techniques that might answer a even few more questions weighing on your mind.
Good luck with your fire-blocking project. I’m always here if you have any questions about your basement project! Just leave me a comment below and respond the same day!