Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
Thank you both for sharing your info, Brian and talman. I have bookmarked this thread for future reference. After reading about crawls, I would much prefer having a slab over a crawl or a basement.
All of the foundation options have their pros and cons.
The biggest advantage to a slab is a lower cost of construction. The biggest disadvantage I would cite is that it's hard to get to the things beneath the slab when needed. A simple plumbing leak can turn into a major job involving tearing up the floor to get to the pipes. Parts of the HVAC often ends up in the attic, creating an opportunity for the same types of problems you could have in a crawl (leaks, condensation), yet in a more perilous place (where water can leak onto the rest of the house causing damage), and of course in the event of flooding or drainage problems, water on the main floor is a much more costly problem to have than water in the crawl.
That's not to say slabs are bad or unmanageable, they are just a more value oriented option where a crawl space is a more premium option at time of build. Basements could be considered a "premium plus" option, however they can become more of a liability if located in areas where the water tables are too high, and because the cost of adding a basement is much higher than a crawl, the return on investment is rarely there. Again fixing a drainage problem that's impacted a crawl is typically a lot less expensive than dealing with significant water damage to a basement and the foundation problems that can occur.
My personal preference is for crawl in southeastern climates. I might take a basement farther north. If a liked a home and it was on a slab and the rest of the conditions are right, I would give it fair consideration.
What these guys say is what echos what folks I know in the construction industry have said. The accessibility of a crawl makes many things easier.
While I can certainly appreciate the argument in favor of crawls, my education and experience has led me to quite different conclusions in these matters. I speak to some of my distastes for them in Donna's recent crawlspace encapsulation thread. There are many great links on this subject and the problems with crawlspaces in general.
I disagree that slab equates to any price or budget orientation. To me, it equates with the most value regardless of price: its the easiest method of controlling ground moisture, bulk water and soil gases, including Radon. Almost all basements include slabs. While up north, they are often justified for frostline considerations, here they are more topography related. A well built daylight basement has little risk of flood concerns as long as its not in a floodplain.
I would rather spend more money to have a slab. Like on a typical crawlspace lot (sloping 1-7' across corners) fill the stepped stemwall with clean gravel and pour a slab opposed to any type of crawlspace. This give you awesome subslab drainage and easy areas to keep depressurized with a simple plumbing stack, minus the fan that you have with an active system, more often needed with crawls.
The cost to properly encapsulate and provide conditioning can approach basement costs depending on the details. The air in these spaces are never as good as the air above and the on-going costs to condition and monitor it should be considered just as much as the accessibility concerns.
Accessibility is the best reason but I think its importance is over-blown. HVAC is accommodated in floor truss systems and soffits when necessary. Most new homes are insulating the roof deck and even with attic floor insulation, burying the ducts can be a good solution so the attic is easily available if needed.
The "comfort" air distribution arguments are mute to me as we use very efficient envelopes with third party engineers sizing the system and best practice duct installation. With modern homes it just doesnt take that many CFM to condition spaces so any distribution near a window is the main concern, not whether it comes from above or below. As triple pane windows become common, we wont even need to get the ducts near the window. With a new well-performing home, you should barely feel any air from the supply registers.
Plumbing supply comes from underground, just like it does from the meter, very little need to ever access the supply line from meter to shutoff in house. Waste lines are the main thing that cause the most disruption to change or repair. This kind of work makes DIYers and handymen shutter as its usually beyond their scope. I think its these types that seem to dismiss slabs for those reasons. Hire a professional and this is typical light construction work. Most commercial buildings are on slabs as are most homes in this country. Its really not that big of a deal should you ever need to change that stuff, especially since youre likely involved with major renovation anyway.
I argue that crawls are INaccessible. Show of hands for all those who have crawled to the far corners of their crawlspaces lately? Do you think that electricians, plumbers and HVAC techs are doing their best work in these spaces? The cramped conditions lead to crap work that lends itself to needing access because it was done poorly!
Health relating to joint pain? A common complaint yet no one has ever shown me any research lending validation. I think the closest thing is studies pointing to dog's toenail problems and all such concerns should be applied to other hard surfaces like tile. I strongly disagree that wood or wood framed floors make much of a difference. Orthopedic insoles should be the main strategy for this concern as it relates to all floor finishes. The only finish I notice a big difference is carpet with thick padding and thats probably the worst thing you could pick for indoor air quality concerns.
Cold floors? We include R10-R14 foam under our slabs which makes them very close to the same temperature as the indoor air, reducing chances of condensation, and creating another redundant barrier to soil moisture and gases like radon.
As in most things construction, all people have opinions on the details. Those are some of mine for whatever its worth.
I guess we've heard two different opinions here on slab vs. crawl, and like I said there are pros and cons to each. A slab can be more expensive to fill on a slope as you pointed out, as a general rule throughout NC a crawl will cost more. All of the crawls I've been in throughout my lifetime were fairly easy to access everything, or at least things that needed to be accessed. Usually the important systems to work on are not placed in the hardest to reach corners, so that part I will disagree with. I go to every corner of my crawl (some of the areas I must be on my stomach and parts I can almost walk standing up) so I could show my hands there. 95% of the things I would need to work on are in the easy-stoop range.
I don't agree that getting to the plumbing in a slab is light construction work from the perspective of a homeowner. If someone has installed expensive hardwood floors, its going to be very painful for the homeowner to tear them all up to get to the plumbing, and I don't mean from the perspective that the labor itself would be hard since that is likely to be handled by professionally anyway -- I mean simply watching and incurring the cost and inconvenience of the floor tear up. That reason alone is why I have a slight bias against slabs, but I do still see the pros and cons of each. As you mentioned basements have slabs but they typically have pipes, duct work, electrical and such in easy to reach places.
So, like I said, one man's opinion only and there are no shortage of opinions. As evidence of that, just get on Youtube and search for crawl vs slab to get a feel for all the varied opinions. Some folks like the ability to add heating elements to slabs. Some people think they feel too hard on the feet with a lack of "give" when walking.
Anyone that's in a crawl or slab home should not feel the need to change where they live because they've talked themselves out of liking their foundation choice. Pros and cons to each its just a matter of forming an unbiased opinion based on research. I admit personal bias -- I like accessibility. Builders that specialize in slab homes will tell you those are better, builders that specialize in crawls will tell you those are better. Better to form our own opinions we are happy with.
Great points and well spoken for team crawlspace. I do encourage people to read the opinions and recommendations of building scientists and researchers studying these issues. I think you may be hard pressed to find these types that prefer crawlspace to slab. Bottom line for me: slab typically has better indoor air quality.
Why not? I saw in the other thread that you were considering this for a brand new house -- that means you're way on top of matters compared to most homeowners. Most people often don't even start to consider crawlspace humidity until decades later or think about radon until they're already terminal with cancer. You have plenty of time to assess, shop around, and act. Monitor it for a year or so if it takes some stress off.
And don't pay $5k-8k for these items, I saw those quotes in another thread. Nuts.
Great points and well spoken for team crawlspace. I do encourage people to read the opinions and recommendations of building scientists and researchers studying these issues. I think you may be hard pressed to find these types that prefer crawlspace to slab. Bottom line for me: slab typically has better indoor air quality.
I would agree that indoor air quality becomes simpler with a slab, I don't know about better though. Is the indoor air quality of a standard slab home better than a home with a sick crawlspace? Yes, but I am suggesting that sick crawlspaces be remedied. Indoor air quality can be solved a number of ways, some of which are quite inexpensive (UV lights installed in the HVAC system, etc). If a crawlspace is moldy that needs to be addressed, but mold can occur in slab homes from flood water which has sat against the home as opposed to having the opportunity to seep through vents in the crawl, so mold risk doesn't go away and termite risk escalated with a slab (harder to inspect).
Ack! Here I go again getting off topic The debate of slam vs crawl really is timeless, and I'm well aware there's no clear cut answer or the industry would have just gone one way or the other long ago.
Just curious though, aside from mold and radon (common to all foundations), what indoor quality issues would you be most concerned about?
It is a fun topic that brings out a lot of passion in folks. How our homes are attached to the ground beneath has been agonized over for millennia. Donna, dont despair you really are ahead of the game by being wise to these issues.
Those prices for crawlspace encapsulation are market average for an average size house I think. Its a lot of work in awful conditions and its tough to get all the details right. The high expense is why its a difficult proposition to do in the first place. Like I say, better to fill er with gravel or build a basement.
It depends on the details but I think its safe to say that an average crawlspace is more at risk of mold/mildew and overall humidity problems than a slab. Pick any vented crawlspace with a few years on it, the amount of issues you are likely to find will be exponentially higher than a home on a slab.
Our region's humidity does not play nicely with the wood framing and finishes in cave like environments (cool and damp). Seal the vents up, do your best to separate the ground with plastic, and do whatever it takes to condition it appropriately which includes monitoring and possible adjustments. This is out of most homeowners comfort zone or level of giving a damn which means most crawlspaces are doomed for the same issues that so many building researchers are finding problems with.
Iam not sure I follow why a slab would be more at risk for flooding. Problems (which are usually small leaks) can be more quickly diagnosed. Subfloors and framing are more at risk of rot than concrete. Leaks getting past the slab drain harmlessly through the gravel, leaks past a subfloor pool or soak in the crawlspace area which increases the humidity levels and associated problems there. Higher groundwater from heavy rain events are easier avoided with a raised gravel layer drained to daylight. In a crawlspace, it can be trickier getting the correct drainage to daylight (because of sub-grade conditions) and getting the water to flow out instead of soak the ground that surrounds and more heavily influences the indoor air.
As for the relative hassle of replacing finish flooring I dont know why you would need to be changing anything under there. If you are moving plumbing waste lines, then you are probably rearranging walls or doing other things that will require the finished flooring be fixed or updated anyway. Many commercial spaces undergo far more changes than residential yet you wont see any new commercial foundations on crawlspaces.
I agree that there are many ways of improving indoor air quality, namely the fresh outdoor air exchange required by international building codes but not yet enforced locally. There are many methods of reducing indoor air pollution. Crawlspaces contribute to higher humidity, higher chances of mold/mildew and more risk or tougher remediation of radon and other soil gases. They also contribute to higher energy costs which is not good for outdoor air quality either.
All that being said, we are getting close to starting a home with a crawlspace. You better believe it will be un-vented and well detailed to deal with the myriad of risks and concerns that come with it. While I made my case to the homeowner, an UN-vented crawlspace seems to be the best fit for the site and their needs. Had I been involved in the design stage, we probably could have ended up with a different design on a walk-out basement. This would have been a better fit for the attached cave concerns, a good fit for the site and the space created would be far more useful.
Thanks everyone,
Sometimes I just get overwhelmed with this house. I lived in a condo for the majority of my life and did not have any of these issues to worry about. I argued with this builder many times about their method for installing finishes in my house. Their answer was, "this is not a custom home". I started researching vented crawl spaces back in February, but it would have been too late to change the foundation. I am all about "green living" and that is my number one priority in my house. My plan is to encapsulate my crawlspace.
This move has caused a lot of changes in a short period of time. I have not driven a car in many years and had to get used to driving in the mountains. I have never had grass to cut, gutters to clean or snakes to avoid. It is a little overwhelming at times. I am trying to take one step at a time.
I moved here without knowing anyone and have no one to turn to for advise or support. I am a strong person, but we all need help sometimes. Thanks to all of you, I don't feel alone.
Donna
BK & talman could charge for this tutorial thread...
Remarkable collection of good info, imo.
Our crawl, though 8 mil covered way back when it was built, is on my list of Stuff to Do/Fix here at our Mtn joint.
Thanks to both for very good, informative threads.
GL, mD
Please register to post and access all features of our very popular forum. It is free and quick. Over $68,000 in prizes has already been given out to active posters on our forum. Additional giveaways are planned.
Detailed information about all U.S. cities, counties, and zip codes on our site: City-data.com.
Please register to participate in our discussions with 2 million other members - it's free and quick! Some forums can only be seen by registered members. After you create your account, you'll be able to customize options and access all our 15,000 new posts/day with fewer ads.
The debate of slam vs crawl really is timeless, and I'm well aware there's no clear cut answer or the industry would have just gone one way or the other long ago. 
