Installing a Basement Window - Cutting Concrete Block Foundation

Basement Egress Window - Cutting Concrete Block To Install A Window
Typically we would hire a concrete company to cut foundations for us, but that can get costly at rate of $1600 a day. Using a gas cut off saw was also an option, but this house is occupied and we thought it best to avoid the exhaust from the engine.
We finally settled on using a Husqvarna 9-inch cordless cut off saw. This saw runs on batteries and does not pollute the house with fumes. Click here to read the tool review on the Husqvarna 9-inch Cut Off Saw.
Because this saw has a 3-inch depth of cut we knew we would need to make these cuts from both-sides of the wall.
Measuring The Windows - Layout
We were going to install the windows side by side with a 2x4 between the two for a nailer and to accommodate a small amount of trim. The windows would be installed within a frame of 2x8 pressure treated framing lumber.
To determine our framing rough opening, we placed the windows on the floor, with a 1-1/2” space between the two and measured the width and length, adding 1" to the width and ½” to the height measurement, for plumbing and shimming. Once we had this measurement the next steps was to figure out the framing measurements.
We added 6 inches on the width of the opening to accommodate two 2x8 jack studs on each side. We decided to cut the bottom of the window on a mortar joint that would allow us to install a 7-1/4 inch header on top of the window. Adding these measurements to our rough opening measurement gave us the total concrete block to cut.
Preparing - Cutting Concrete Block To Install Window
With the total measurement figured out we transferred this measurement to the concrete block wall, and leveled and plumbed out marks on the wall with a permanent marker. The marker does not wash off like chalk does, and is darker and easier to see over pencil.
Once the window was marked out on the inside we used a Makita hammer drill and drilled through holes in the concrete block at all corners. These holes were then used on the exterior of the wall to locate our cut lines. We repeated the step above on the outside.
We then set up a water hose to our saw for a concrete block wet-cutting operation and had a wet vacuum ready to collect the slurry.
Cutting the Concrete
When cutting an opening in an existing block wall, try to align it with existing mortar joints.
We used the saw to score the line and then to make a 3-inch deep cut on both sides. Once complete we used a sledge hammer to break the concrete blocks at the score line.
Once you've opened up the wall, you'll have a number of partial concrete blocks that will need to be filled in with mortar or replaced.
We brought the window opening lower than needed to be able to break the opening at a mortar joint, and to allow for a 7-1/4” header above.
Repair the opening as required, adding wire mesh to the cavities to give your mortar something to hold on to, or install a pressure treated ”wood buck” and secure it in place with Tapcon masonry screws.
NOTE - we installed a 2x6 pressure treated "wood buck" into one cavity and secured it in place with concrete screws. We were then able to nail our framing to this buck.
Fastening The Framing To The Concrete
We used pressure treated lumber in all areas that contact the concrete. 2x8 pressure treated lumber was used, and the first piece installed was the rough framing sill. We chiseled as needed, leveled and installed a 2x8 sill plate in the opening. The sill was then fastened to the concrete block with 3-inch Tapcon concrete screws and a hammer drill.

[@gregcolegrove3366]

Thans Rob! I was going to help my son cut a hole in a cinder bloc wall for window and door. I wanted to see how real contractors did this, and as soon as I saw a video with how YOU did this, i knew i'd get the real info on how to do it correctly-- Thankyou!

[@hior12israel49]

I'll need to watch a few times to build confidence, but I appreciate this video

[@larrysherman5254]

As a firefighter for many years, with technical rescue training, we were always taught, when breaching a block wall, to start breaking out the blocks from the bottom and work up. If you start at the top, all the debris falls into the voids of the lower block, and by the time you get to the bottom, you're trying to break out what is almost solid concrete. It wouldn't have made a big difference in this particular situation because of the small amount of actual block removed, but someone cutting an opening for an egress window or door in a wall with no previous openings, starting at the bottom would make the job easier. Plus, I've seen instances where starting at the bottom, gravity becomes your friend, mortar joints will crack from the vibrations, and some blocks will fall out without being touched.

[@ConcordCarpenter]

Larry Sherman great tip sir thx for your service

[@Jesus-Santana]

Ií😮😮😮😮66h7c44e4,

[@fjeinca]

Great comment, thank you! 💙

[@FinishCarpentryTV]

The wife wants me to do this to our house. looks like I'm gonna need some more tools! Good work guys!

[@zrafferty]

Only reason we can buy tools !!

[@NB-Philly]

I plan to replace my standard door in my basement to a siding glass door or two French doors, and potentially adding a larger window as well. Should the main support where the door is currently be strong enough to put in a door frame double the width minus the blocks I’ll be removing?

[@NB-Philly]

@Finish Carpentry, I love your channel! I’ve learned so much from both this and your amazing content!

[@JB-ez2jz]

Great video for those (even pros) who are wary about cutting block or rock. I know I was intimitated the first time I did it and a video like this then woulda been awesome!

[@ConcordCarpenter]

Joey DaFish thx

[@michaelkubert8522]

This video is perfect for my project. Thank you! You gave great info and I am able to envision my own project more clearly now.

[@brent7261]

What about affecting the structural foundation of the house? How do you know if you cut a hole too big the house could collapse?

[@funkybasstrix]

Thanks Rob, you are so detailed in your description of your work I feel like I can do that job by myself.

[@peterjackson2115]

Do you require a jack post on each side with a temporary support beam until the header is installed ? What’s the maximum width you recommend for a basement window for egress and natural light

[@hotsaucehimself]

Thanks. Inspired and informed me so I can diy the cutting! Thanks!

[@Amara6]

Wow, you guys nailed it. Good job.

[@throwerr]

Would of been nice to see an actual video of cutting and the installation

[@MNCasaPro]

Good work. I'm surprised you didn't have king studs at the outside to stabilize the header and tie everything together. I've never seen jack studs used without kings before. Thanks for the video.

[@ConcordCarpenter]

Great point - probably should have

[@emmarestrepobloise9959]

I would love to see the final installation.

[@benchippy8039]

So different to how we do it in the Uk. We use either a concrete lintel, catnip or rsj, the cill might have a brick course with plastic cavity closers up the sides then window fixed directly to the block work but not spanning the cavity. Great vid as always happy Xmas

[@ConcordCarpenter]

Ben Chippy we do that too but not in this situation

[@benchippy8039]

Do you have many block and brick houses where you are? If I was gonna build a house for myself I’d make it timber framed, it just seems like a good balance between longevity and affordability

[@brodacious5850]

For marking longer saw cut lines in concrete use red chalk then spray clear paint over top. You can squeegee the slurry away from on top of the line and it won’t wash the line away.

[@ConcordCarpenter]

brody moore great tip!!!

[@jounoiwon2020]

Thanks for the video. I have a question: when cutting with a circular saw, there will be overcuts on four corners. How do you go about filling the overcuts? thanks

[@olgajoachimosmundsen4647]

How come you did not support the above meanwhile cutting the hole? How important is it that the preassure-treated wood in this instance is dry?

[@ConcordCarpenter]

Olga & Joachim Osmundsen pt wood is code so we use it- not sure how important it is in this particular situation

[@paulvisschedyk9177]

Thanks, Rob. Very useful. I tore down a brick-fireplace wall, which exposed the rough, oversized, concrete opening of the basement window. The blocks were all 'rough-smashed' and very uneven. I chipped the mortar away to a semblance of 'more-level', but am reluctant to start chipping away at the blocks. Your video gave me the idea to lash a piece of 2x lumber to the wall to build a 'mortar-bed', on which to set the rough-sill, and go from there with the framing.

[@Dave_Simmons]

What do you do for squaring off the corners? I'm looking into cutting an opening in a solid concrete brick wall.

[@BlackfeatherAlexander]

Bro you always have the best videos. Super enthusiastic!

[@Froggerty]

Is it possible to cut the block without water? We have rooms already built in our basement and we need to install two egress windows. Yikes!

[@jerryjohnsonii4181]

Very interesting an thanks for the knowledge !!!!!!!! Also have a Happy Merry Christmas !!!!!!!!!!!!!!!!

[@brettbenson563]

Fantastic, great information. Thank you.

[@sfuchs]

Which windows sets did you eventually install? Those blck Anderson at 5:00? What's the point fitting different set first?

[@nateg5915]

Great video. Very helpful. Now can you use that same concept to add a whole door to a basement nd turn it into a walk out basement? Of course the outside would have to be excavated nd concrete stairs be added...is that something that is possible?

[@ConcordCarpenter]

Nate G we cut a door in too, that’ll be another video

[@NRB_75]

Why do companies leave the cutout concrete on bottom of hole before backfilling

[@gomake1939]

Hey Rob, I’m going to do this job this week. What’s the labor rate for a job like this?

[@7205buttas]

I have a cement walkway around my entire house. How can I install a egress window? Do I need to cut not just threw the brick foundation but also the walkway?

[@ConcordCarpenter]

not sure

[@jeffcoolhd]

It's called an extension jamb. That's my tech tip for the day. Peace brother

[@ConcordCarpenter]

Lol proper nomenclature got it.... - I got tongue tied

[@jeffcoolhd]

@@ConcordCarpenter I knew you knew that was the extension jamb. I thought you would get a good laugh out of me correcting you. Hey you and your family have a great Christmas and thank you for a great year of videos. Peace brother

[@ConcordCarpenter]

Makita man merry Christmas brother

[@rbondy008]

Another great video. How did the cutter hold up in the "real world"?

[@ConcordCarpenter]

rbondy008 it’s slow cutting but we knew that going into it, and saves $$$ from sub contracting it out or renting a faster, larger too. It took 2 batteries to cut both sides

[@robroby10]

Thank you, very informative

[@lennysantucci2177]

You could also use a 14in electric demo saw

[@ConcordCarpenter]

Lenny Santucci didn’t want to rent it

[@ethanupton8375]

how do you finish out the exterior

[@musichound1974]

In the video, How did you support the buck board into the supporting brick foundation. Any Suggestions to have it fastened securely. Sorry if this question has been asked/answered. Be safe.

[@ConcordCarpenter]

Large Tapcons

[@kiwdwks]

Awesome...thank you!

[@carlosvids7473]

Solid work!

[@OthmanAlikhan]

Thanks for the video =)

[@ConcordCarpenter]

You’re welcome thank you for commenting and supporting the site please consider subscribing

[@EM-fi2qg]

2:05 I'm curious why you overcut the 2x6 so much? Was there sag when you cut out the block?

[@ConcordCarpenter]

E30 M3 there was a gap between and sill beam and we wanted header tight to the sill, on

[@sfuchs]

@@ConcordCarpenter there was a gap between. ..... and sill beam. What was the first part?

[@j.ericsmith]

How to finish the header on the outside wall? Stucco?

[@ConcordCarpenter]

We trimmed it with pvc flat stock casing and a sill

[@andrewgoldin6905]

Is a concrete block wall load ever bearing?

[@ConcordCarpenter]

Yes

[@mehardeepsingh5190]

Where’s the lintel?

[@matthewcatalani4088]

block wall is a joke to cut , can use skill saw with concrete blade , but great video, for diy folks

[@davidkeele2679]

How did you build your header?

[@ConcordCarpenter]

Four 2X8 header

[@nelson1tom]

Is the pressure treated lumber used because its dimentionally stable?

[@ConcordCarpenter]

Tom Nelson masonry contact

[@nelson1tom]

A Concord Carpenter / ToolBoxBuzz Thanks!

[@MrTooTechnical]

Where was the temp wall while cutting so the house didn’t cave in? Nice vid

[@ConcordCarpenter]

dave daved if you look at what was there prior 0:34 you’ll see the old window was up tight to the 6x8 sill, directly above that is a triple wide window with a modern LVL header spanning past this window left and right.

[@nateg5915]

Wait. Is that even possible for the house to cave in by just removing a couple feet of the block foundation?

[@MrTooTechnical]

I want to see the temp wall. Enough said

[@ConcordCarpenter]

Nate G not really, and definitely not in this situation

[@alexdavidson7785]

👍

[@guitarplayerdonald7546]

Come to my house.👍

[@RobertGSolomon]

Funny you didn't fill the cider block with concrete and wire mesh like you talked about, What a joke when people talk about how to do something but video themselves not even doing it!!! Can you answer as to why this was not done?>