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With regard to list of approaches to managing humidity do you feel a " raised slab" is preferable to an "encapsulated crawlspace with a dehumidifier". It appears so on your list. Almost all the "custom builders" will do the encapsulated approach and claim the benefits of future access and softer flooring outweighs the "raised slab" approach. ( seems that the semi custom guys with lower price points go raised slab) Also your flooring options are limited to engineered wood or tile as you cant nail down real wood floors to " raised slab". There are a few old, but very well established builders ( with 30+ years) that claim a well vented crawl space is the only way to build as humidity balance and letting the structure and floor breathe is the best long term solution. I know this issue has been debated elsewhere on the blog but curious about thoughts
Everything can vary. Economy, cost of labor, cost of material and so on can play a part.
Cost: A raised concrete slab is about ¼ the cost of a crawl space. Ask a builder if they want to build a 250-thousand-dollar house or a million-dollar house. Most all will want to build bigger. Builders profit margins run anywhere from 15% and up or they would not be in the business. Every dollar you spend is money in their pocket.
Soil Condition: Wet? Dry? Height above sea level? Flood zone? Most coastal areas are going to be wet, somewhere between 10 and 30 feet above sea level and probably in one class of flood zone or another. In St James there are marsh lands (flood plains), ponds, the Intra Coastal Waterway (ICW) and the soil is generally sandy. Water drains but in many areas, this takes time from a few hours to days. The ground is most likely wet and may be prone to flooding even if it’s only once every 100 years. This brings in the issues of flood insurance and flood vents. Flood water can have tremendous pressure that can literally push a house off its foundation. Flood vents allow water to run under and through a foundation, relieving the pressure and preventing or reducing foundation damage. They are generally required in garages and crawl spaces if the house is in a flood zone.
Crawl Space
Pros
Easier to route heating and cooling ducts and plumbing.
Easier to remodel heating and cooling ducts and plumbing. (How often is this done?)
Floors are warmer. (Perhaps, generally not an issue in areas where the temperature seldom reaches freezing for more than a day or two at a time)
Cons
Can allow for entry of roaches, spiders, snakes, mice, and mold/mildew.
Additional construction techniques and mechanicals needed to reduce/prevent moisture and humidity possibly including:
• Foam encapsulation
• Heavy vinyl ground cover with forced ventilation under (requires constant electrical demands).
• Dehumidifier (requires constant electrical demands and drainage for water it collects)
• Sump pump(s) (requires electrical).
In addition to the added cost of building the crawl space, now these services are added increasing the cost further plus continued electrical costs and maintenance.
An added benefit of crawl space encapsulation is less dust inside the home, cleaner air, no insulation in floor joists (HVAC warms and cools crawl space just like the rest of the house which actually reduces heating and cooling costs).
(If cost is not an issue, then it is debatable as to whether encapsulation is the best long term solution. It is certainly a viable solution).
Clearance from grade to floor joists. Though some contractors like to sell a crawl space they will then make it minimum height. After all the services are installed it can almost impossible to navigate in a crawl space to do anything unless there is at least 24” or more clearance.
Raised Slab
Pros
A solid space of dirt and concrete, no vermin, no mice or insects.
No place for mold or mildew to grow.
No maintenance.
No flood vents, no water under house.
Also, keep in mind there are some remarkable concrete finishes today that can make bare concrete look like wood, tile, and other finishes. This may not be the thing to do in a living room but porches, decks and patio areas can be made very attractive with the proper finish.
If the home is in a flood zone, then almost all mechanical's go high into attic spaces for 'top down' construction. Should moderate flooding occur, then very little gets wet. This will reduce flood insurance and ultimately, damage in the event of a flood.
Cons
Floor comfort. Concrete is hard and has less give. However, good quality carpet padding, engineered woods etc. give some flex back. Some people are more sensitive to hard floors than others. Many people spend their working careers on concrete floors, or walking on sidewalks, in Walmart etc. and never pay it any mind. You do not walk that much in your home. The most time is spent sleeping and sitting and the mile or so you may walk inside your house each day is trivial and you will probably never notice the difference. Also, note that hardwoods can be added to raised slab during design and construction. Joists (called sleepers) can be placed over the slab, then plywood, then hardwoods. The trade-off is perhaps a bit of ceiling height. Instead of 10 foot now they are 9.5 foot.
Maybe be cooler but generally not an issue in warm climates.
I have discussed this issue with several St. James builders during the the interview process and have heard several options of foundation design. As DitchOC mentioned in his previous post, the most important factor in determining the type of foundation for a home is the presence, or the possibility of standing water on your lot.
IMHO, if standing water is an issue, the raised slab would seem to be the best option as it would alleviate the possibility of water interacting with the structure.
The lot that we purchased does not appear to have any water issues (we were down for a week over the summer, and I drove over to the lot at the end of a very heavy rain, and no water present).
In our case, we are having an encapsulated, non-vented, crawlspace with a supply line of conditioned air to the crawlspace. This eliminates the need for floor insulation as the crawlspace air has the same properties as the air in the living space. It also eliminates the need for a commercial type dehumidifier that would need to be constantly monitored and eventually replaced. From the research that I have done, this method is recommended for the Energy Star Certification.
I'm not a big fan of engineered hardwood floors or walking on a concrete slab for the next 30 years (hopefully!) so that's another factor that steered us toward the sealed crawlspace
Another consideration is the the material that will be placed on the crawlspace floor (with a slab on grade or raised slab this would obviously not be a factor). From my understanding 10 mil plastic is the typical application to seal the floor. To provide a greater barrier to moisture, a rat slab can be poured basically creating a little basement. Obviously, this would add to the cost but would provide additional room for storage as well as the benefits of further reducing moisture penetration.
Once you have determined if water is an issue on your lot, then it is just a matter of researching the various options to determine what is best for you and you new home.
With regard to list of approaches to managing humidity do you feel a " raised slab" is preferable to an "encapsulated crawlspace with a dehumidifier". It appears so on your list. Almost all the "custom builders" will do the encapsulated approach and claim the benefits of future access and softer flooring outweighs the "raised slab" approach. ( seems that the semi custom guys with lower price points go raised slab) Also your flooring options are limited to engineered wood or tile as you cant nail down real wood floors to " raised slab". There are a few old, but very well established builders ( with 30+ years) that claim a well vented crawl space is the only way to build as humidity balance and letting the structure and floor breathe is the best long term solution. I know this issue has been debated elsewhere on the blog but curious about thoughts
NJCali,
Here is the link to the Energy Star Standards. I believe the foundation info. can be found on page 4
I visited my lot a few days after the big Hurricane in October and there was no puddling or evidence of erosion from run-off. . Also my elevation is about 26ft over sea level and not in the flood plain map. My thinking is the moisture issue may be manageable but not simple or fool proof decision. . My builder ( and several I've spoken too) are highly recommending encapsulated crawl space( with dehumidifier ) for the softness and access issues. We are still in planning stages and we are leaning towards a hard ceramic/porcelain floors in most the first floor area so if i dont have the benefit of a softer floor then should i still be thinking of poured foundation?
Ill ask about the Energy star approach and/ rat slab , neither option did i see in prior discussion
If comfort under foot is not an issue, the slab would probably be a more economical choice as compared to an encapsulated crawlspace. The slab would also provide an excellent substrate for the tile you are planning to install. However, areas of concern regarding the slab relate to the loss of additional storage (probably minor) and the fact that future modifications to plumbing and electrical could be difficult as these utilities may run through the slab.
If you decide to go with a slab foundation, whether it be raised or on grade, it will be important to give critical thought during the planning process to the placement of plumbing (and possibility electrical) runs, otherwise you risk the possibility of having to break up the slab to reroute the lines.
I would think if you wanted the flexibility of joists to make the floor give with the benefit of having a raised slab, the builder could simulate joists by running a 2x4 frame on the slab and laying the flooring on top. It is a little unconventional but it would probably work.
Also, note that hardwoods can be added to raised slab during design and construction. Joists (called sleepers) can be placed over the slab, then plywood, then hardwoods. The trade-off is perhaps a bit of ceiling height. Instead of 10 foot now they are 9.5 foot.
Here is one link to some detail (you can find others, just google "sleepers over concrete slab")
The main disadvantage is cost. You saved money by putting in a slab but then put a 'traditional' framed floor on top of it which will add cost. The final finish of tile, hardwoods/parquet, carpet would pretty much be the same except now you have a wooden floor between you and the concrete.
Reminds me of the area where I built my first house. It was on a rural, 2 lane numbered road. The road was widened to 4 lanes, then a shopping center went in, then another. Other businesses sprang up, then an industrial park along with 3 or 4 new stop lights. All this took place over about 15 years and the rural area I had built in turned into a business corridor. I moved on but I have to say my home value roughly tripled during the time I had it. Depending on your view point, that may all be a good thing or a bad thing but change is inevitable. Brace yourself.
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