How to Frame a Basement
1. Use good lumber for the studs.
The framing for your new finished space is one of the most important components. The new drywall will conform to the framing, so it must be plumb, level, and straight. You definitely don't want to use old or bowed studs that will deform your walls.
2. Keep all untreated wood away from concrete surfaces.
Since most basements are inherently moist, you need to keep all untreated wood away from concrete surfaces. Moisture below the slab can wick up into the concrete and get to the base plates of the wall. This is why you need to use treated lumber for the bottom plate of the wall.
3. Make sure wall studs don't come into contact with the foundation wall.
The cool concrete of the foundation wall will collect humid air, which will condense on its surface. This moisture will wick into any lumber that comes into contact with it. So make sure the framed wall has a gap between it and the foundation wall.
Check out our video at the bottom of the page for frame-quality-check details when finishing your basement.
4. Use the right vapor barriers.
A common question people have when finishing a basement is "Should I use visqueen or plastic sheeting on one side or the other of the framed basement walls?" The answer is no. Plastic will prevent moisture from moving through the wall. As we mentioned earlier, the basement is naturally humid because of its lower location. So moisture can and will get inside the wall. If you use plastic, the moisture will be trapped inside, which lead to damage to materials and even mold.
5. Use the right type of insulation at the band joist.
The band joist—sometimes called the rim joist—is the wood framing that runs along the outside perimeter of the first floor framing. We want to make certain this area is properly insulated properly. Make sure the band joists above the walls have either fiberglass insulation batts or foam insulation covering the entire space.
The photo below shows foam insulation used at the band joist on a finished basement in progress. Foam insulation is preferred over fiberglass as it has a higher R-value, is resistant to moisture, and creates better air seal.
6. Cover all wall cracks first.
Obviously, you will want to repair any structural problems with the foundation walls prior to covering them up. You will also want to repair any water leaks. But what about cracks in the wall?
Before starting a basement finishing project, every square inch of the walls should be reviewed for cracks and leaks.
Cracks in the foundation wall? A poured foundation wall crack may or may not go all the way through the wall. Even if the crack does go all the way through the wall, it may still be dry. Newer waterproofing materials are more pliable and will many times span cracks to keep groundwater out. Unfortunately, there really is no way to tell if the crack is finished moving.
If a foundation wall crack continues to move and the waterproofing seal on the outside is broken, water can enter. This could be disastrous for a finished basement wall. The leak may go undetected for a period of time which can cause damage to materials and possibly mold. So it's always a good practice to repair any foundation cracks prior to covering the walls up.
Common Questions About Framing Your Own Basement
Should there be a gap between the basement wall and the framing?
Yes, there should be a gap. Make sure wall studs don't come into contact with the foundation wall to prevent moisture damage.
Should I use visqueen or plastic sheeting on the framed basement walls?
No you should not, as plastic will prevent moisture from moving through the wall and will lead to mold and damage.
What kind of lumber should I use?
For the studs, use new lumber to ensure flat walls. Use treated lumber for the bottom plate of the wall (where the stud meets the floor).
What is the best insulation to use at the place where the basement wall meets the floor above?
This area is called the band joist, and you can use either foam or fiberglass—but foam is better, as it has a higher R-value, is resistant to moisture, and creates better air seal.
Do I need to worry about cracks in the basement wall?
Yes, you should fill all cracks before you start putting in the studs.
Tips for Building a New Home With a Finished Basement
So if you're building a new home, there are some items to incorporate into the foundation that will make for a better finished lower level:
- Install visqueen under the complete basement slab and tape the joints.
- Consider adding insulation to the outside of the basement wall—this can serve as protection for your waterproofing also.
- Waterproof the outside of the foundation wall. Don't just use the code minimum damproofing.
- Consider installing an interior and exterior drain tile connected every eight feet through the footer, as this will add redundancy to your drainage system.
- Add a battery backup to your sump pump.
- Use the best sump pump you can find (Zoeller makes a good pump).