When you’re adding a new space to your home, what’s under your floor is just as important as what’s on it. For our master bedroom addition, we’ve been laying the groundwork, literally. From pouring concrete piers to installing a smart French drain system, we’ve been focused on building a strong, dry, and long-lasting home addition foundation.
Concrete Piers & Perimeter Beam Walls
We kicked things off with a classic pier and beam foundation, which is ideal for homes in our area. This setup gives us a handy crawl space underneath the new bedroom, which helps with future access and airflow. We poured concrete piers and built a perimeter beam wall that will carry the weight of the entire room addition 
Drainage is Key – Inside French Drains and River Rock
With the structure in place, we turned our attention to drainage, because keeping water out is one of the most important parts of a successful foundation drainage solution. We installed French drains inside the perimeter wall to prevent water from pooling under the house.
Then we covered those drains with river rock, carefully grading everything so that water naturally flows toward a central collection point.
It’s one of those systems you’ll never see again, but trust me, when the rains come, you’ll be glad it’s there!
It Looked Like a Swimming Pool!
Next came the moisture barrier: we rolled out a thick 60-mil membrane liner across the entire crawl space. I joked with my husband that it looked like we were lining a pool!
But this liner plays a big role in moisture control in the crawl space, keeping things clean and dry underneath the addition.
Bonus? It makes future access way easier if we ever need to get under the house again.
Termite Shields: Fact or Folklore?
Another must-have in our area is termite shields, metal caps that sit on top of each pier.
Some say it’s solid science, others call it good building folklore. Either way, it’s a step we never skip. We topped it off with treated base plates for extra durability, giving those wood-to-concrete connections extra protection from pests and moisture.
A Smart Drainage System
One upgrade we’re especially excited about is our new French drain collection system: a 24-inch-wide, 5-foot-deep central drain that gathers all the water from inside the perimeter. It pumps directly into our septic system, which means no more standing water under this house, ever.
Starting the Framing
With the foundation sealed, drained, and termite-resistant, we were finally ready to prep for framing. We installed termite shields on the perimeter beam wall and laid down our treated base plates.
This sets the stage for floor joists and subflooring, which we’ll dive into in the next blog.
Stay Tuned!
We’re just getting started with this master bedroom addition. The foundation work may not be flashy, but it’s one of the most important parts of any home remodeling project. We’ll share how we built the subfloor, picked our framing materials, and tackled a few unexpected surprises along the way (because there’s always something, right?).
👉 Planning your own home remodel or room addition project?
Drop your questions in the comments. I’d love to hear about your plans and help where I can!
That’s a lot! I would have never guessed that there was that much in a foundation! Looks great!