Your Guide to Daylight Basements

Is a daylight basement right for your log home? We examine the key factors to consider.

Written by Dan Mitchell

Photography by Iriana Shiyan

It’s not uncommon for a log home to sit on a rolling, sloping piece of property. Though this kind of land typically comes with spectacular views, it also can create some construction challenges — especially when it comes to digging and laying the foundation. But one huge advantage this kind of topography has is that it often affords having a daylight basement in the home.

If you find that a daylight basement is a possibility for you, take advantage of it! Will excavation cost you a little bit more? Yes. Will it cost more for your foundation materials than a slab or a crawl space would? Yes. But the square footage and functionality that you gain can be far more valuable than the price tag.

As an example, let’s use a standard appraised value of $100 per square foot that a finished daylight basement could give you. If you leave the basement unfinished, the value would be approximately $55 per square foot and it would drop to $35 per square foot for a crawl space with a slab. Of course this all depends on how elaborately you finish the space, but the point is that your value (and overall enjoyment of your home) can increase tremendously for just a little extra investment.

So You Want a Daylight Basement … Now What?

First, you have to examine your soil conditions. For instance, if your site is very rocky or the bedrock is close to the surface, the cost of excavating (even blasting) that lot to create the basement could be far more expensive than any dollar value you’d add to the house by creating that extra square footage (i.e., return on investment).

Next, take a look at the actual slope of your land. The slope sweet spot for daylight basements is 6+ feet in grade elevation from the front of the house to the back. This has to do with the ultimate height of the basement and how far down you’ll have to dig. For a finished daylight basement, you’ll want a minimum of an 8-foot finished ceiling, so if your slope is less than 6 feet, you’ll either have to dig a much deeper foundation hole or it will be sticking out of the ground quite far, which could look unappealing. The more you have to dig, the more it will cost.

Advantages & Disadvantages

Full-height, daylight basements have a number of advantages over their slab and crawl-space cousins, but for all their good points, there are a handful of disadvantages to consider, too. Weigh the pros and cons:

Pros:

The ability to push guest bedrooms down below, allowing you to save money on a smaller overall footprint (just make sure each bedroom has a point of egress, like a door or window well, as required by code).
More space for game rooms, home theaters, gyms and other entertainment areas.
A practical place for a mechanical room, so you don’t have to sacrifice square footage on your main living area to a water heater or furnace. It also affords a “safe room” for natural disaster emergencies.
Space to stash your stuff — and we all have stuff — that’s much more convenient to access than if it were stowed in a crawl space or an attic.
Increased overall square footage/increased home value.

Cons:

Potential property-tax increases.
Risk of a leaky basement (depending on material, proper construction and waterproofing), which could lead to mold growth or water damage.

A way to save money on daylight basement costs is to install a three-sided foundation against the walls that are touching the earth (these are retaining walls) and frame out the exposed wall, which only has to bear the load from above, with 2-by-4s or 2-by-6s.

Material Options

Concrete is the standard material for foundation/basement construction, but there are several concrete options to consider.

Concrete Block.

Also called concrete masonry units (CMUs), this is the least expensive material you can use for a daylight basement; however, it takes the longest to install, which could drive up labor costs. Also, since each individual block is held together with mortar, CMUs have the greatest chance to shift and/or the mortar could be breached. It also will have to be waterproofed, insulated and enclosed, and conduit will be necessary to prevent electrical hazards. It’s a very good value if you’re not planning to finish the basement as livable area.

Pour-in-Place Concrete.

This technique involves installing aluminum forms into the ground, then pouring liquid concrete into them, allowing it to cure and removing the forms. (Think of it as a sidewalk that’s turned on its side.) Cost-wise, it’s a middle-of-the-road option, but once installed, it will still have to be waterproofed inside and out. And, if you want to finish it, like CMUs it will have to be insulated and enclosed to be livable. This can drive up expense. It also can be a slow process, requiring as much as 30 days to set the forms, pour the concrete and allow it to cure before you can build on it.

Precast Concrete.

In this system, concrete is poured into reusable forms at an offsite location, trucked to the job site and hoisted into the prepped ground with a crane. This can be a challenge — even impossible — for some sites, as the crane may not have a place to operate safely. Precast is similar in cost to pour-in-place, but it’s by far the fastest installation. No onsite curing time is needed, so you can start laying your subfloor right away.

Insulated Concrete Forms (ICFs).

If your intention is to have a finished basement that’s comfortable and dry, give ICFs serious consideration. Comprised of reinforced concrete sandwiched between thermal insulation that stays in place as part of the finished wall system, they are the most expensive option upfront, but they also offer the best value, because they save time on construction and no additional insulation is required, reducing finishing costs dramatically. Plus, their insulation capabilities and energy-saving properties are exceptional, which could save you a considerable amount money down the road.

So as you can see, not only can a daylight basement bring you years of enjoyment, it also can increase your property value. Weigh your options carefully, and you’ll see the light.

Dan Mitchell is a builder, Log & Timber Home University professor and the 2018 President of the Greater Knoxville Home Builders Association. He owns Eagle CDI in Tennessee.