FHB Logo Facebook LinkedIn Email Pinterest Twitter X Instagram Tiktok YouTube Plus Icon Close Icon Navigation Search Icon Navigation Search Icon Arrow Down Icon Video Guide Icon Article Guide Icon Modal Close Icon Guide Search Icon Skip to content
Subscribe
Log In
  • How-To
  • Design
  • Tools & Materials
  • Restoration
  • Videos
  • Blogs
  • Forum
  • Magazine
  • Members
  • FHB House
  • Podcast
Log In

Discussion Forum

Discussion Forum

Crawl space height

alfie | Posted in General Discussion on August 15, 2007 12:43pm

For a crawl space, what would be a suitable clearance height from slab to bottom of floor joists above?

New construction. Due to site conditions, I had to give up the desired basement. Was thinking of building on slab, but am concerned about the loss of future flexibility. Thought about a trench in the slab, but future flexibility would still be limited. Going with a crawl space would enable access for all the usual things now and in the future. It would be conditioned space (see Building Science Corp. web site for more on that), insulated and with a slab.

What would be a reasonable crawl space clear height that one could actually get around in, for those infrequent (hopefully) occasions that something needs to be done? I was thinking something like 36-42 inch min. Comments?

Reply
  • X
  • facebook
  • linkedin
  • pinterest
  • email
  • add to favorites Log in or Sign up to save your favorite articles

Replies

  1. Hiker | Aug 15, 2007 01:01am | #1

    I would make the space as tall as you can bear to.  We recently completed a house with a similar strategy and installed all the mechanical in that space.  Worked out real well and allowed for cathedral ceilings throughout the house and infinite flexibility for additional wiring, moving plumbing and not bad storage area either.

    1. alfie | Aug 15, 2007 01:09am | #2

      I hear you. Ideally I would make it 7 or 8 feet tall and turn it into a basement. The problem is water, and ledge. So the question is really to get to the optimal trade-off between go deeper and invite problems (and expend $'s), or go shallower and regret it every time I have to go in there to do something.

  2. JohnSprungX | Aug 15, 2007 01:37am | #3

    16" = Minimum allowed by code

    24" = Easy crawling on hands and knees

    36" = Easy to sit on you butt and work on things at joist level

    42" = More of a stretch from sitting down

    48" = Definitely bring a 5 gallon bucket to sit on.

  3. calvin | Aug 15, 2007 01:52am | #4

    alfie, remember to deduct headroom for any known mechanicals that might pass under the joists and any beam.  I've had just enough room to work in some, but not being able to get under that trunk line makes it difficult.

    After you get done, buy a creeper with long rope to leave down there.

    A great place for Information, Comraderie, and a sucker punch.

    Remodeling Contractor just outside the Glass City.

    http://www.quittintime.com/

     

    1. alfie | Aug 15, 2007 03:17am | #6

      Thanks for the responses. 36 sounds like a reasonable min to shoot for, don't know about mechanicals yet. What's the rope for? OK, I've never used a creeper.

      1. calvin | Aug 15, 2007 03:24am | #7

        Mechanics creeper-lay on your back and roll around.  The rope, so you can load up the creeper and pull it across that beautiful concrete crawl floor.  And of course so you can pull it back to the entry in case you forgot.

        And lights................

        with a switch.

        And an outlet.

         A great place for Information, Comraderie, and a sucker punch.

        Remodeling Contractor just outside the Glass City.

        http://www.quittintime.com/

         

        1. alfie | Aug 15, 2007 03:31am | #8

          Thanks. I had figured out the creeper in my head. Thought one just kind of paddles it around. Now I can see that the rope would be handy. Will probably put several strategically located outlets down there, and at least a couple of lights that can be switched on right from the access.

          1. alfie | Aug 15, 2007 03:33am | #9

            check out this v-drop creeper:
            http://classic-motoring.stores.yahoo.net/vmecr.html
            Seems to me that the extra comfort might be welcome.

          2. calvin | Aug 15, 2007 04:33am | #10

            On occasion there's creeper repair in my shop.  My buddy and mechanic ships one home with every so often........when one gets run over.A great place for Information, Comraderie, and a sucker punch.

            Remodeling Contractor just outside the Glass City.

            http://www.quittintime.com/

             

    2. JohnT8 | Aug 21, 2007 06:48pm | #33

      After you get done, buy a creeper with long rope to leave down there.

      Why the He!! didn't you mention something like that a year ago?!  The hundreds of hours I spent in the current crawlspace ... creeper wouldn't work, but one of those garden deals would (seat with wheels for moving along flower borders).  I never even thought of it.

       jt8

      "Democracy is two wolves and a lamb deciding what to have for dinner, liberty is a well armed lamb protesting the vote."  -- Benjamin Franklin

      1. calvin | Aug 21, 2007 07:12pm | #34

        John, we can't be all things for all people.............

        Have a hard enough time thinking of that kind of thing for my own benefit.A great place for Information, Comraderie, and a sucker punch.

        Remodeling Contractor just outside the Glass City.

        http://www.quittintime.com/

         

  4. Dave45 | Aug 15, 2007 02:20am | #5

    Sixteen inches is the minimum and more is usually better.  I'm working on a remodel and addition right now that will have ~18" - 20" below the floor joists.  The HO and I both agreed that 16" was ok 25 years ago, but that's just not enough anymore.

    My house has 16" (max) and when we moved here in '79, I was all over the place under there running TV antenna wire, stereo speaker wires, additional phone lines, etc.  I only had to scoop out one place to get under a heating duct. 

    About five years ago, I needed to rerun some phone lines, home run the cable TV, and clean out the dryer vent.  I found that my house had settled quite a bit over the years!!  It was a chore getting anywhere under there!!

    When I finished and came back out, I mentioned the settling to SWMBO.  She gave me "the look" and sweetly asked what size jeans I was wearing that day - and what size I wore in '79. - lol

  5. User avater
    popawheelie | Aug 15, 2007 07:12am | #11

    Our last house had 40" with sand on the ground. Very nice!

  6. User avater
    loucarabasi | Aug 15, 2007 01:10pm | #12

    Go 40inches, About nine years ago we did this large project, The crawl was 12 inches. My guys had to start at the opening with buckets a small shovels and take out 10inches of dirt. It was brutal. It was like 1800 sqr ft. I took 5 days if I remember. The BI said we were crazy. He suggested lifting the house. We were the talk of the bi department, but i saved a boatload of $. The job came out perfect. I'm good friends with the BI now and he'll bring it up on accasion (he says- What were you thinking?).

    -Lou

    1. alfie | Aug 15, 2007 05:14pm | #13

      Thanks. This is the the kind of fine tuning I am looking for. For new construction, going from 36 inches to 40 inches will hopefully not make much of a difference unless we run into any conditions. But for something, someday I'll likely be glad for the extra inches. At construction time, if possible, I'll be looking to increase even more if I can.

  7. renosteinke | Aug 16, 2007 04:30am | #14

    An interesting catch-22 ... too deep, or not deep enough, and it will be a PITA to work in. So....

    Assume the 'crawling' position. How high are your shoulders? Take that measure, add a foot, and ther should be enough room to move about, even under the ducts.

    In some places, such as near the sewer line, I'd make it deep enough to easily slide under the line.

    Three things are, to me, more important than simple depth.
    ACCESS: Access holes typically require the body to make too many turns, in too small a space. The well ought to be large enough for you to assume the crawling position, and be even with the inside.
    FLOOR: ought to be firm, level, and dry. Make sure it drains away from working areas.
    LIGHTING: Don't be cheap.

    1. alfie | Aug 16, 2007 01:22pm | #15

      Thanks. I take your point on access, which was the worst part of the crawl space in the last house I had. I'm going with an insulated slab, so that solves the floor problem. On lighting so far I am thinking anything that projects below the bottom of joists above would be in the way. Thoughts on type and location of lighting?

      1. renosteinke | Aug 16, 2007 04:20pm | #16

        I agree with placing the lights between the joists. Personally, I use 'keyless' fixtures, with spiral fluorescent bulbs. They ought to all be controlled by a single switch near the entry- and get an illuminated switch! I locate one near the entry, one positioned to light every piece of equipment where it will be serviced, and perhaps others to light the path (if it's of any distance".

        Edited 8/16/2007 9:21 am ET by renosteinke

        1. alfie | Aug 16, 2007 04:30pm | #17

          Thanks. Those are useful suggestions.
          PS: what's a keyless fixture?

          Edited 8/16/2007 9:40 am ET by alfie

          1. renosteinke | Aug 17, 2007 12:39am | #23

            For some reason, lost in the mists of time, the cheap porcelain fixtures that simply hold a bulb and attach to junction boxes have been called 'keyless.'

          2. alfie | Aug 17, 2007 01:32am | #24

            Thanks. I've met those fixtures. Just didn't know that's what they are called.

          3. DanH | Aug 17, 2007 01:47am | #26

            Because they don't have a switch, which used to look a bit like a key, I suspect.
            So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin

          4. alfie | Aug 17, 2007 01:50am | #27

            I was thinking of that too. Sounds plausible.

  8. IdahoDon | Aug 16, 2007 04:55pm | #18

    Wow, a 4' crawlspace with a slab.  Can't imagine the cost vs benefit works out on that, but not a full basement.

     

    Beer was created so carpenters wouldn't rule the world.

    1. alfie | Aug 16, 2007 05:18pm | #19

      First of all, 3-foot-ish, not quite 4. A highly technical spec there! The problem is ledge and water. Go to the depth of a basement and I will be dealing with water issues from surrounding wetlands, as well as ledge. The choice is between building on slab for a lower cost and lesser future flexibility and maintainability, or building with a crawl space. A reasonably comfortable crawl space height is a wish. So the cost vs. benefit analysis should really be between 16" height (folks indicate that is the absolute min) and 40" which seems to be desirable. What are your thoughts?
      Regarding the slab, if I do a crawl space, it will be conditioned space. Read Building Science Corp's web site http://www.buildingscience.com for some great material on construction. No need for me to reproduce that here.

      1. IdahoDon | Aug 16, 2007 06:19pm | #20

        I'm very familiar with conditioned crawl space and that's definitely the way to go over venting.

        I'd base the crawl space height on how often you'll be down there (seldom), what's code (18" as per IRC with an 18" x 24" access), and what's going in the space.  If duct work is hanging all over then more room is better to get around the ducts, but if most ducts are upstairs then the extra room probably doesn't matter much.

        If storage is tight in other places, an extra deep crawl, conditioned and  with a slab is pretty handy.  If long-term storage of rarely used items is considered then the deeper the crawl the better.  It frees up valuable space in other parts of the house.

        You can also use crawl space for your mechanicals, again freeing up valuable space upstairs.  Gaining a modest 20 sqft of floor space on the main floor, at $200 a sqft in value, is likely to increase the appraisal of your house by $4,000.

        Personally, I'd go with a slab on grade for the whole house and simply preplan for some future additions.  It's dirt cheap to put in some extra water and plumbing lines for future use.  Conduit of all sizes can also be placed for cheap.   The money saved over a crawl will pay for a cruise for you and the mrs.

        Good building

          

        Beer was created so carpenters wouldn't rule the world.

        1. alfie | Aug 16, 2007 07:00pm | #21

          I expect that I won't be down there very much, particularly after the first year or two when things settle down. That said, I seem to always be tinkering, pulling cables and generally trying to alter the state of affairs.Once I reconciled, painfully, to abandoning the basement, it seemed the slab was the smart/least-expensive way to go. Two things that impacted my thinking on a slab were future adaptability/maintenance, and the health code. What if the stuff you buried in the concrete, say the sewer lines, has a problem and you have to get it out and replace. On flexibility there are a couple of future possibilities and yes extra plumbing lines ahead of time could address that. What if I want to pull cables for an elaborate sound system, or stuff like that. and who knows what else. I agree that conduits and stuff don't cost much up front. Things have a way of not being where you want them when you need them!Re. extra plumbing lines, the health code (CT) says that any stub-outs etc. that could create a bathroom and a bedroom will be included in the bedroom count toward occupancy supportable by the septic system. I am interpreting from memory, not a literal quote. I kind of like the future flexibility, particularly adapting to aging. My interest is long term.I may change my mind on the resolution of slab vs. crawl space, and welcome comments. Every time I think it is settled, new information or perspective opens it up again.

          1. michaelindc | Aug 17, 2007 12:21am | #22

            I don't know if it's usual or not, but in my house the main water shut-off valve is in the crawl, which is a huge PITA. I recommend a remote-control for the valve if that's the case.

          2. alfie | Aug 17, 2007 01:52am | #28

            I wouldn't want any controls in a crawl space. I like to be able to get stuff like that readily. An expedition to the crawlspace does not qualify for that.

          3. IdahoDon | Aug 17, 2007 01:46am | #25

            ...count toward occupancy supportable by the septic system...

            That would make sense!  No reason to build an undersized septic system from day one.

            As for the cost, if you pencil out the crawl vs slab, especially if using a frost protected shallow foundation, the cost savings are significant.  You're talking about saving $2000 in slab cutting down the road with a crawlspace vs. many times that in savings today with a slab.  Truth be told, if the saving were invested in mutual funds today, the capital gains alone would easily pay for the cost of cutting the slab down the road.

            Nope, it doesn't pencil out anyway other than your piece of mind to be able to tinker, not that that's not important.  If you just like being in a crawlspace, more power to you.

            best  

            Beer was created so carpenters wouldn't rule the world.

          4. alfie | Aug 17, 2007 02:04am | #29

            I share the view on not undersizing things. In this case, I would do a swap. Suppose I wanted to add a bedroom for single floor living in the future, I'd take one away from elsewhere.For the record, crawl spaces are not amongst my favorite places to be in.The slab is again beginning to look better. I reviewed the design drawings and it looks like a couple of strategically placed trenches/channels in the slab could address the most likely future scenarios. If some really odd needs arise, that would be the time to start cutting up the slab. Keep in mind though, that besides cutting the slab, one would have to deal with restoring finishes, and there would be a quite a mess.The desire for tinkerability may turn out to be rather expensive to cater too, as you point out.

          5. JohnSprungX | Aug 21, 2007 04:09am | #30

            >  For the record, crawl spaces are not amongst my favorite places to be in.

            But this is a *conditioned* crawl space, 40+ inches high, with a slab floor, lights, and plugs.  Hell, I'd stick a mini-fridge in there for  beer, maybe hang a flat screen TV from the joists....  ;-)   This is one posh crawl space.

             

            -- J.S.

             

          6. DanH | Aug 21, 2007 01:13pm | #31

            Yeah, OK until you need to take a cr*p.
            So convenient a thing it is to be a reasonable Creature, since it enables one to find or make a Reason for everything one has a mind to do. --Benjamin Franklin

          7. alfie | Aug 21, 2007 05:22pm | #32

            There's an idea. A keg or barrel might work well too. Then, one could crawl up to it, open the tap, and simply let gravity do the trick.Not clear where the plus in the 40+ came from. Perhaps it is the space between the joists. I'd find it hard to raise a glass to my lips, wedged in between joists 16" OC. Also, with 36-40 inches from slab to joist, one might have to squeeze a bit to get past ducts etc. Some care might be necessary to minimize spillage of beverages.Personally, I am all for posh.

  9. Rockford | Aug 21, 2007 11:27pm | #35

    I think you need to also consider your overall building hieght restrictions (if there are any).  Where I live I'm limited to 26' grade to ridge so I kept my crawlspace to a minimum, which for me was about 24", or about three 2X8s on the footing forms.  Of course, you can always excavate the entire area, so it doesn't have an effect on building height, but that can be pretty costly.  You'd be surprised how quickly the cubic yards start adding up when they start digging.

    This has worked out just fine for me and I'm pretty big and didn't really have a problemmm getting around.

    1. alfie | Aug 21, 2007 11:37pm | #36

      Thanks. For us it is 35'. Usually there so any factors suggesting one thing or another. I am hoping that as the project comes together, the course of action will become clearer.

Log in or create an account to post a comment.

Sign up Log in

Become a member and get full access to FineHomebuilding.com

Video Shorts

Categories

  • Business
  • Code Questions
  • Construction Techniques
  • Energy, Heating & Insulation
  • General Discussion
  • Help/Work Wanted
  • Photo Gallery
  • Reader Classified
  • Tools for Home Building

Discussion Forum

Recent Posts and Replies

  • |
  • |
  • |
  • |
  • |
  • |
View More Create Post

Up Next

Video Shorts

Featured Story

FHB Summit 2025 — Design, Build, Business

Join some of the most experienced and recognized building professionals for two days of presentations, panel discussions, networking, and more.

Featured Video

How to Install Exterior Window Trim

Learn how to measure, cut, and build window casing made of cellular PVC, solid wood, poly-ash boards, or any common molding material. Plus, get tips for a clean and solid installation.

Related Stories

  • Fight House Fires Through Design
  • Making the Move to Multifamily
  • Custom Built-ins With Job-Site Tools
  • An Easier Method for Mitered Head Casings

Highlights

Fine Homebuilding All Access
Fine Homebuilding Podcast
Tool Tech
Plus, get an extra 20% off with code GIFT20

"I have learned so much thanks to the searchable articles on the FHB website. I can confidently say that I expect to be a life-long subscriber." - M.K.

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Fine Homebuilding Magazine

  • Issue 332 - July 2025
    • Custom Built-ins With Job-Site Tools
    • Fight House Fires Through Design
    • Making the Move to Multifamily
  • Issue 331 - June 2025
    • A More Resilient Roof
    • Tool Test: You Need a Drywall Sander
    • Ducted vs. Ductless Heat Pumps
  • Issue 330 - April/May 2025
    • Deck Details for Durability
    • FAQs on HPWHs
    • 10 Tips for a Long-Lasting Paint Job
  • Issue 329 - Feb/Mar 2025
    • Smart Foundation for a Small Addition
    • A Kominka Comes West
    • Making Small Kitchens Work
  • Issue 328 - Dec/Jan 2024
    • How a Pro Replaces Columns
    • Passive House 3.0
    • Tool Test: Compact Line Lasers

Fine Home Building

Newsletter Sign-up

  • Fine Homebuilding

    Home building tips, offers, and expert advice in your inbox.

  • Green Building Advisor

    Building science and energy efficiency advice, plus special offers, in your inbox.

  • Old House Journal

    Repair, renovation, and restoration tips, plus special offers, in your inbox.

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters

Follow

  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X
  • Fine Homebuilding

    Dig into cutting-edge approaches and decades of proven solutions with total access to our experts and tradespeople.

    Start Free Trial Now
    • Facebook
    • Instagram
    • X
    • LinkedIn
  • GBA Prime

    Get instant access to the latest developments in green building, research, and reports from the field.

    Start Free Trial Now
    • Facebook
    • YouTube
  • Old House Journal

    Learn how to restore, repair, update, and decorate your home.

    Subscribe Now
    • Facebook
    • Instagram
    • X

Membership & Magazine

  • Online Archive
  • Start Free Trial
  • Magazine Subscription
  • Magazine Renewal
  • Gift a Subscription
  • Customer Support
  • Privacy Preferences
  • About
  • Contact
  • Advertise
  • Careers
  • Terms of Use
  • Site Map
  • Do not sell or share my information
  • Privacy Policy
  • Accessibility
  • California Privacy Rights

© 2025 Active Interest Media. All rights reserved.

Fine Homebuilding receives a commission for items purchased through links on this site, including Amazon Associates and other affiliate advertising programs.

  • Home Group
  • Antique Trader
  • Arts & Crafts Homes
  • Bank Note Reporter
  • Cabin Life
  • Cuisine at Home
  • Fine Gardening
  • Fine Woodworking
  • Green Building Advisor
  • Garden Gate
  • Horticulture
  • Keep Craft Alive
  • Log Home Living
  • Military Trader/Vehicles
  • Numismatic News
  • Numismaster
  • Old Cars Weekly
  • Old House Journal
  • Period Homes
  • Popular Woodworking
  • Script
  • ShopNotes
  • Sports Collectors Digest
  • Threads
  • Timber Home Living
  • Traditional Building
  • Woodsmith
  • World Coin News
  • Writer's Digest
Active Interest Media logo
X
X
This is a dialog window which overlays the main content of the page. The modal window is a 'site map' of the most critical areas of the site. Pressing the Escape (ESC) button will close the modal and bring you back to where you were on the page.

Main Menu

  • How-To
  • Design
  • Tools & Materials
  • Video
  • Blogs
  • Forum
  • Project Guides
  • Reader Projects
  • Magazine
  • Members
  • FHB House

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Podcasts

  • FHB Podcast
  • ProTalk

Webinars

  • Upcoming and On-Demand

Popular Topics

  • Kitchens
  • Business
  • Bedrooms
  • Roofs
  • Architecture and Design
  • Green Building
  • Decks
  • Framing
  • Safety
  • Remodeling
  • Bathrooms
  • Windows
  • Tilework
  • Ceilings
  • HVAC

Magazine

  • Current Issue
  • Past Issues
  • Magazine Index
  • Subscribe
  • Online Archive
  • Author Guidelines

All Access

  • Member Home
  • Start Free Trial
  • Gift Membership

Online Learning

  • Courses
  • Project Guides
  • Reader Projects
  • Podcast

More

  • FHB Ambassadors
  • FHB House
  • Customer Support

Account

  • Log In
  • Join

Newsletter

Get home building tips, offers, and expert advice in your inbox

Signing you up...

This site is protected by reCAPTCHA and the Google Privacy Policy and Terms of Service apply.
See all newsletters
See all newsletters

Follow

  • X
  • YouTube
  • instagram
  • facebook
  • pinterest
  • Tiktok

Join All Access

Become a member and get instant access to thousands of videos, how-tos, tool reviews, and design features.

Start Your Free Trial

Subscribe

FHB Magazine

Start your subscription today and save up to 70%

Subscribe

Enjoy unlimited access to Fine Homebuilding. Join Now

Already a member? Log in

We hope you’ve enjoyed your free articles. To keep reading, become a member today.

Get complete site access to expert advice, how-to videos, Code Check, and more, plus the print magazine.

Start your FREE trial

Already a member? Log in

Privacy Policy Update

We use cookies, pixels, script and other tracking technologies to analyze and improve our service, to improve and personalize content, and for advertising to you. We also share information about your use of our site with third-party social media, advertising and analytics partners. You can view our Privacy Policy here and our Terms of Use here.

Cookies

Analytics

These cookies help us track site metrics to improve our sites and provide a better user experience.

Advertising/Social Media

These cookies are used to serve advertisements aligned with your interests.

Essential

These cookies are required to provide basic functions like page navigation and access to secure areas of the website.

Delete My Data

Delete all cookies and associated data