Turning a Crawl Space Into a Basement? Read This First!


Ever wonder what it might take to turn your crawlspace into a livable, usable space? While it could create a whole new space for your family, carving out a basement from a crawl space is an undertaking that requires more than just a weekend and a couple of friends.

When turning a crawl space into a basement, follow these steps:

  1. Plan your project and ensure you have an engineer’s approval.
  2. Get approval/permits from your municipality.
  3. Dig around the outside of the foundation down to the footings
  4. Raise the house structure with hydraulic jacks, i-beams, and cribbing
  5. Pour a new foundation wall or lay a new block wall for the basement
  6. Pour a concrete slab for the new basement floor
  7. Lower the house onto new foundation walls and remove cribbing
  8. Waterproof interior and exterior basement walls
  9. Backfill against exterior basement walls
  10. Complete interior finishing with framing, drywall, etc.

In this article, we’ll go over all the considerations you need to factor into a job, like converting a crawl space into a usable area. We’ll also go over the time and cost it will take to complete this job and other options for changing your crawlspace into something more practical.

Turning Crawl Space Into Basement

Can You Turn a Crawl Space Into a Basement?

You can turn a crawl space into a basement. You will have to dig up your foundation, raise your house, pour a new concrete wall and concrete slab, then finish it off by waterproofing, backfilling the exterior, framing, and interior finishing details.

But why change a crawl space into a basement? For starters, it adds an entire new floor of living space for your home. Yes, you could add a floor to your house, but many homes are not engineered to have another floor on top of it, making your only choice raising the house.

Also, having another floor adds tons of value to your home, as you would then be able to add a bedroom and bathroom, at a minimum, to your existing home. In that case, you are adding tens of thousands of dollars to your home’s value, if not more.

Another thing to keep in mind is that many homeowner insurance policies treat crawl spaces differently than basements – meaning that damage to crawl spaces due to water is often not covered. Basements, as living spaces, are often covered for various types of water damage.

Pros Cons
  • Increases value of your home
  • More living and storage space for your family
  • Covered by home insurance
  • Easier to access utilities such as pipes and furnace
  • Huge Cost
  • Messy, time-consuming job
  • May have to leave house temporarily for the job to get done
  • Permitting and approvals may take time
  • Yard will be completely torn up

Do You Need a Permit for Crawlspace to Basement Conversion?

You will need a building permit from your municipality, along with the signature of a professional structural engineer stamped onto the building plans. Your local utilities may also need to come out to mark out utilities indicating where the contractor can dig or not.

Municipalities require building permits from homeowners to ensure buildings are safely constructed and renovated. Converting a crawlspace to a basement has massive ramifications for your house, and the work must be done carefully by trained professionals.

DIY CrawlSpace Conversion

Can you convert your crawl space into a basement yourself? It is possible, but you’ll need some heavy equipment and lots of friends to help. The hardest part will be raising the house, as you’ll need industrial hydraulic jacks and beams that span the width of the house. Then you’ll have to operate the jacks – carefully – ensuring your house is raised evenly on all sides.

This type of project isn’t typically considered a DIY operation. Even after the house is raised, you’ll then need to pour a new foundation wall and marry it to the existing wall. Creating the forms, laying the rebar, and pouring requires know-how that most DIYers simply don’t have.

How to Convert a Crawl Space to Basement – Step by Step

Crawlspace to basement

Like any renovation that adds significant value to a home, a crawl space conversion will temporarily turn your home into a construction site. The amount of equipment and manpower needed to do the job means that your house will be unusable for some time.

Step 1: Plan and Get an Engineer’s Approval

Your first step in the process will more than likely be consulting with a contractor to get a quote for the job. The contractor may or may not ask if you already have plans for the new basement. If not, the contractor may have an engineer to do the work for you.

You can seek out a structural engineer separately to get them to draw up plans for your crawlspace conversion. They will need to come out to your house and take detailed measurements and see any pre-existing plans. Be prepared to pay, however, as this will cost anywhere between $500 to $2000.

Once you have certified plans from the structural engineer, you can bring them to any general contractor. They will give you a quote, and then the job begins. Get many quotes, as bigger jobs will have a greater variance in estimates than smaller jobs.

Remember, check the references of contractors – just because they “specialize” in foundation repair does not mean they specialize in raising houses.

Step 2: Get a Building Permit

Once you have a contractor in place with plans and approvals from a structural engineer, you can apply for a building permit. While this process is different depending on your municipality, most will require a stamped building plan, a very detailed lot diagram, a properly surveyed lot, and information about the contractor.

Permits are another cost, and they can be anywhere from $50 to $300 – or more – depending on the municipality.

Some jurisdictions may not allow homes to be raised for whatever reason, so be prepared to have some back and forth with the building inspectors before you get approved.

Step 3: Dig and Expose the Exterior Foundation

When the work begins, the first step will be to dig out the exterior of the foundation. Depending on your lot’s geography, this may require very little to quite a bit of digging. The entire foundation must be exposed, all the way down to the footings.

You must dig to the footings for two reasons: the first is that when the wall is completed, you’ll need to waterproof the entire foundation wall, down to the footings. Secondly, sections of the crawl space wall may need to be removed to anchor the jacks that will raise the house.

It is recommended to backfill with ¾” gravel when the job is complete, as this will help drain water away from the new foundation.

Step 4: Raise the House

The most invasive part of the job is lifting the house. There is no uniform height of a crawl space, but most range from 2’ to 5’ high. Ideally, you want to raise the height of the building to have a basement with a 7’ clearance when complete.

Remember that you’ll be pouring a slab after the house is raised, so you must account for the slab thickness – at least 3”.

The contractor will place a series of hydraulic jacks in key places beneath the home to lift the house. If your crawl space has a dirt floor, they’ll first have to pour temporary concrete footings for the jacks to rest on.

All electrical and plumbing that extends into the crawlspace will have to be detached at this point and any fasteners holding the house framing onto the crawl space wall. The jacks will then move up a few inches at a time, all controlled by one operator on a truck.

The large beams will be placed on top of each other in alternating directions – called cribbing – up to the bottom of the house. As the jacks move house up, the cribbing also is raised so that it eventually supports the house temporarily as the new walls are built.

Step 5: Make a New Foundation Wall

Convert crawl space to full basement

To build a new foundation wall, you can either pour a new foundation atop the old one or use cinder blocks to create a new wall.

If you opt to pour a new foundation wall, the contractor will build forms from plywood or styrofoam, lay rebar in the forms, then pour. A concrete mixer will come to your house and deliver the concrete.

If you opt for a block foundation wall, the process will take much longer as several people have to lay the blocks.

Step 6: Lower House and Remove Cribbing

Now it’s time to lower the house back onto your new basement exterior walls. The contractor will slowly lower the hydraulic jacks and cribbing until the house is resting on the new walls.

Once the house is affixed to the new foundation walls, re-install any plumbing, electrical, and HVAC removed before the lifting. This will require an electrician and plumber, as the building inspector will want to see who completed the work before he signs off on the completed project.

Step 7: Pour a New Basement Slab

Crawl space conversion

While this might be done before the walls are complete, allowing for easier concrete delivery, it would be difficult with all the cribbing and jacks beneath the house. Instead, pouring a new slab through an opening – like a window – in the foundation wall is ideal.

Slabs should go up to the level of the footing or just above. It should be a minimum of 4” thick. At this time, any type of sump pump or waste pump should be installed before pouring the slab.

The contractor will ensure that the slab is finished to a smooth surface. Drying will take several days, so during this time, no interior work can be completed. Exhaust fans may be used to speed up the process.

Step 8: Waterproof Interior and Exterior Walls

Waterproofing Exterior Walls

Waterproofing foundation walls should begin from the exterior. You’ll need a protective membrane that adheres to the exterior walls. This can be accomplished with bitumen-based foundation self-adhering wraps. Many require primers before installing and should cover the entire wall.

At the base of the footing, perforated drains should be installed – weeping tile – that wrap around the perimeter of the footing. At one corner, the drain will go under the house to connect to a sump pump.

After the membrane and tile are installed, the contractor should install a dimpled membrane that is fastened to the walls with concrete screws. This provides a final layer of waterproof protection for your foundation.

Step 9: Backfill Exterior Basement Walls

Backfill with clear ¾” gravel provides ideal drainage for your basement walls and allows your weeping tile to operate without the risk of clogs from silty soil.

The last 6” or so of the earth should be topsoil, which sits above the gravel.

The ideal grade is at least ½” per foot of distance away from the house. This should be the rule for at least the first 10’ of distance from the house.

Step 10: Complete Interior Finishing

Now it’s time to move inside and finish off your brand new living space. For starters, you’ll have to frame the perimeter of your basement and insulate.

While there are many options for insulation, such as spray foam, you can stick to standard 16” fiberglass insulation.

How Much Does it Cost To Turn Crawlspace Into Basement?

When broken down into individual components, it isn’t surprising that converting a crawlspace into a basement can push six figures.

Plans, Permits, Approvals

The permit and planning can cost as little as $500 if you live in a rural area. Those who live in large metropolitan areas with more rigid building codes and a higher cost of living, expect to pay somewhere in the neighborhood of $3000 to get your crawl space reno off the ground.

Excavation

The shallower your crawl space, the cheaper the job. However, the entire perimeter of your house must still be dug out, and any deck or patio must be moved. Therefore the absolute minimum for this job will be around $5000. If lots of decking must be removed and you have a deep crawl space, you will look at $20000 if you also want the dirt removed.

House Raising

If your house is larger, with two stories, then the house raising costs are much greater as more supports and jacks will be necessary. Since you are raising the house significantly to create a finished basement, then your house raising costs will be in the neighborhood of $100 a square foot, and possibly much more.

Concrete

The cost of concrete will be roughly $140 per cubic yard. Some areas may be slightly cheaper. This translates to roughly $18 per square foot of concrete if the poured walls are 6” thick.

If the walls are 8’ high and you have a 40’ length of the wall, then the cost of the concrete for that wall is $320. Multiply that times two and you get $640. You are then looking at roughly $1000 in just concrete for the poured walls.

Add an extra $10 per square foot for labor costs, plus $150 per hour for the concrete truck to deliver and mix. Add another $3-$4 per square foot cost for miscellaneous items, such as rebar and other forms. This adds another $3000 to the job, at a minimum.

Finally, don’t forget about the 4” thick concrete slab. This will be around 14 cubic yards of concrete, adding another $2000 to the final tab. Overall, you are looking at a minimum of $7000 for a 30’x40’ house with 8’ poured walls.

Waterproofing

Expect the cost to be closer to $40 per linear foot. If you have a 30’x40’ home, then you can expect to pay somewhere around $5000.

Partial Basement With Crawl Space

If the cost and commitment of a full crawl space conversion to a finished basement don’t suit you, then you can opt for a partial basement. This conversion will look different depending on the type of house you have, although the process is identical to the process mentioned above.

Homes with large grading variations on their exterior are ideal candidates for partial basements, as one end of the crawl space may be deeper than the other. In that case, creating a partial basement on end makes sense.

You may pay a little less if creating a partial basement instead of a full one, but you should still be prepared to pay tens of thousands of dollars for even a partial basement.

Conclusion

Doing a crawl space conversion is no easy task, and it cannot be emphasized enough that your most valuable ally in this renovation is a contractor specializing in this type of job.

The costs listed in this article are only estimates, and as time passes, costs will likely only increase. Make some phone calls to suppliers in your area to get a better idea of costs for materials near you, and you may find that the job is a bit cheaper than you thought.

Remember, a full basement is far more valuable than a bungalow with a crawlspace and you are certain to recover your costs when it comes time to sell.

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