How to Dig Down for Extra Living Space
No room for a ground-level addition? See if a finished basement is a good idea for you
When you're adding space to your home, there are usually three options: down, out or up. Knowing which is right for you means weighing a number considerations — from cost and design, to function and feasibility.
If you're thinking of adding a basement to your home, there's plenty to consider. Safety and stability precautions are different underground than they are on a house's main floors. These eight tips can help you figure out if digging down is your home's best option.
If you're thinking of adding a basement to your home, there's plenty to consider. Safety and stability precautions are different underground than they are on a house's main floors. These eight tips can help you figure out if digging down is your home's best option.
How deep do you need to dig? Basements generally require foundation walls with footing drains and a ceiling that is at least a little more than the height of a standard door (about 7 feet). Many homes with existing basements have ceiling heights lower than this and may have areas where ductwork hanging below the joists makes the ceiling even lower.
Digging down a few feet means removing dirt and concrete, making new concrete footings below the existing ones and pouring a new concrete slab floor. If you are making a new basement where there is only a crawl space, or if your existing foundation is not structurally adequate, it may require lifting your house while the new foundation walls and slab are poured. Even a few inches goes a long way toward making the space feel comfortable. If you can manage 8-foot ceilings, you can use surface-mount light fixtures instead of can lights.
Digging down a few feet means removing dirt and concrete, making new concrete footings below the existing ones and pouring a new concrete slab floor. If you are making a new basement where there is only a crawl space, or if your existing foundation is not structurally adequate, it may require lifting your house while the new foundation walls and slab are poured. Even a few inches goes a long way toward making the space feel comfortable. If you can manage 8-foot ceilings, you can use surface-mount light fixtures instead of can lights.
How do you create egress? Egress simply means an exit in case of an emergency. Building codes determine how big this needs to be and where, but an egress can generally be a large window with a low sill that most people can use to climb out. It can also be a door, which either means digging a concrete stairwell or installing a new door if your home is on a sloped lot. Consult your local building codes for the specifics in your area.
How do you connect to the sewer line? Knowing how deep the sewer line is as it leaves your home will help determine whether you can drain your new basement bath by gravity or need a pump to push it uphill. Even if your waste stacks go down through the concrete slab, you may still need a new pump if you lower your slab by just a few feet.
Your local plumber can help connect the sewer line
Your local plumber can help connect the sewer line
Will there be enough light? Often, installing an egress window means digging a window well. You’ll have more light in that location, but installing additional windows can make your basement feel more open.
There are other tricks, too. Exterior glass doors let light in, while interior glass doors funnel window light into a dark hall. Relites, or interior windows, allow light to filter through to darker interior rooms.
There are other tricks, too. Exterior glass doors let light in, while interior glass doors funnel window light into a dark hall. Relites, or interior windows, allow light to filter through to darker interior rooms.
Where to put the stairs? If you already have a basement, you probably have interior or exterior stairs for access. But just because that’s where someone else put it doesn’t mean that’s where you need it. Relocating the stairs will take up main level space but could free some up as well. Your architect or designer can walk you through the options.
Where will you put the mechanical room? Older homes tend to have 80 percent (or less) efficient furnaces and hot water heaters. These gas and oil-fired appliances need to vent vertically, which means that many of them are clustered around a mechanical chimney or other masonry chimney.
Switching to new 90 percent efficient (or better) appliances comes with two perks: lower utility bills and the ability to place them pretty much wherever you want. These furnaces and water heaters vent horizontally with PVC pipe. That means you don’t have to be near a masonry chimney and will have more layout flexibility.
Consult an HVAC company for your options
Switching to new 90 percent efficient (or better) appliances comes with two perks: lower utility bills and the ability to place them pretty much wherever you want. These furnaces and water heaters vent horizontally with PVC pipe. That means you don’t have to be near a masonry chimney and will have more layout flexibility.
Consult an HVAC company for your options
How will you heat the space? Digging down affords you the opportunity to install insulation under your new concrete slab, greatly improving the basement's energy efficiency.
That new slab also adds the ability to install radiant heat tubes in the concrete. They can be part of a whole-house radiant system or self-contained to heat only the basement.
This system can also supply hot water to the bath and laundry at that level. If you switch to radiant heat for your entire home, you have the potential to gain lots of ceiling height when you remove all that old ductwork.
More:
Contractor Tips: How to Finish Your Basement the Right Way
More Living Space: Making Room for Family
That new slab also adds the ability to install radiant heat tubes in the concrete. They can be part of a whole-house radiant system or self-contained to heat only the basement.
This system can also supply hot water to the bath and laundry at that level. If you switch to radiant heat for your entire home, you have the potential to gain lots of ceiling height when you remove all that old ductwork.
More:
Contractor Tips: How to Finish Your Basement the Right Way
More Living Space: Making Room for Family
Find a good general contractor to manage your basement project