Replacing a crawl space with concrete slab

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First, re-grade & sculpt the yard as well as possible. Mound-up the front to create a dam effect & also create relief gullies along the house sides so surface water can flow readily around the house & can't sit to soak-in. Like, your front door may be a step up from the front walkway, you'd re-grade up to the door threshold & do a flush new walkway. And/or, install a high street curb. And/or, install a Storm Drain with surrounding catch basin or swale that the Town won't...on your property with a large diameter pipe to the back yard or wherever.

Otherwise, I'd have to say totally fill-in the crawlspace & only do gravel & the concrete slab within the joist height. Get the house out of the new "water table" entirely. You won't have joists to ever get damaged again & you'll have an easily replaceable floating wood floor as the only future concern. This would also address any Radon issues you may have.

Of course, institute whatever permanent technologies of waterproofing...

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Suspended slab under construction, with the formwork still in place

Suspended slab formwork and rebar in place, ready for concrete pour. On reinforced concrete blockwork supporting walls

A concrete slab is a common structural element of modern buildings. Horizontal slabs of steel reinforced concrete, typically between 4 and 20 inches (100 and 500 millimeters) thick, are most often used to construct floors and ceilings, while thinner slabs are also used for exterior paving. Sometimes these thinner slabs, ranging from 2 inches (51 mm) to 6 inches (150 mm) thick, are called mud slabs, particularly when used under the main floor slabs[1] or in crawl spaces.[2]

In many domestic and industrial buildings a thick concrete slab, supported on foundations or directly on the subsoil, is used to construct the ground floor of a building. These can either be "ground-bearing" or "suspended" slabs. For Double-storey or Multi-Storey buildings, the use of a few common types of...

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Did You Know?
Termites can build long tunnels in crawl spaces, sometimes as long as 4 feet long, in order to reach timber.

A house foundation, though not one of the most glamorous of parts, is still one of the most important. In fact, it may be THE most important part of your house. After the house is complete, you can repair the walls, paint, and roof with relative ease, but where the foundation is concerned, things are not so simple.

Apart from basement foundations, the other two types of foundations are concrete slabs and crawl spaces. The main difference between these being; while the former involves laying a flat slab under the house, in the latter, the house is raised higher on support beams, resulting in a space below the house that you can 'crawl' into. While concrete is generally used for slabs, for constructing crawl spaces, other materials like timber also have to be used. But when choosing a foundation, you have to go into certain details. Check out...

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All my houses are slab on grade, and generally 2 story.

I do footing - stem - slab. Makes a better job than a monolithic, though both are common around here. Underground plumbing goes in after the stems and isn't a problem, but around here that's the way it's done so the plumbers know what they are doing.

Stem has a step in the top. It's a 6" stem with a double 2X4 blocked to the inside of the form creating a 3" X 3-1/2" step in the top of the stem. 1" styrene is placed in the step and down the inside of the stem to the footing. This isolates the outside of the stem from the slab to diminish heat loss.

4" is plenty strong, in fact much stronger than a framed floor. You don't get a whole lot of deflection in a slab. Bearing locations without stems are handled by thickening the slab, generally over an area about 18" wide, to 12" thick, with 2 @ #4 rebars in the thickened area. This creates a foundation for interior bearing walls that adds nothing but a little...

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The concrete floor

In this design a concrete pad called a “mud pad” is poured on the crawl space floor. This is essentially a concrete barrier meant to help control moisture in the crawl space. This is done several ways; with and with out a vapor barrier. The traditional mud pad is a poured concrete pad over a roughly graded dirt floor. There is little prep work done to flatten the area so the concrete thickness can range from 2” to 6” thick. The final grade of the concrete will appear flat.

A good contractor will install a vapor barrier on the floor prior to pouring the mud pad. This is done because the concrete itself is not a good moisture barrier. Water and moisture will pass through a concrete slab that does not have a vapor barrier with little trouble. The reason this is important is because if a vapor barrier was not used then closing the vents will cause other issues unless a dehumidifier is used. But if a barrier was used, then you will have more...

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The best materials for a crawl space floor are gravel, crushed stone or concrete, with the best of those choices being concrete. Concrete will keep out moisture and bugs. Construction work that might need to be done in the crawl space will be much easier with a finished concrete floor. The concrete should be poured after the footer installation and the foundation walls are in place. Concrete crawl space floors will be difficult to install after framing has begun.

Even though the best crawl space floor is concrete, most crawl space floors are not. The typical floor is simply dirt. The main reason for building a home over a crawl space is to save money. The full basement is a better option, but the additional cost might not fit in to the builder's budget. Crawl spaces are adequate if a proper vapor barrier and ventilation are installed.

To install a concrete slab in a new construction, various steps need to be taken. After the footers and foundation walls are complete,...

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If you want to build your house on a foundation with better curb appeal and resale potential than a monolithic concrete slab, you have three choices. You can go all out and treat yourself to a full basement, save some expense and build over a crawl space, or choose a raised concrete slab. The biggest factor that's likely to influence your decision is money, but it shouldn't be the only one.

1. A Place for Everything

The one unquestionable advantage of basements is the reason that they were invented in the first place: They add usable space to your home. At the very least, they provide a place for items like your furnace, water heater, electrical boxes and other household items. A basement that's properly designed and finished can even add a significant amount of real, practical living space. While some crawl spaces may provide storage space, their use is usually limited, and a house built on a raised slab has no usable under-floor space.

2. Can't Get There...

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Every building has a foundation for that building to rest upon. Basically put, a foundation is the construction that is below the house and ground that supports the weight or load of the house. The type of soil in the region where the home is being built will generally determine what foundation the house will have.

Types of House Foundation

Generally there are three different types of home foundation. The house foundation types are basement, crawl space and slab.

Basement

Generally a basement is partially underground and has a walk-out. Sometimes basements will house the garage. They will have a concrete floor and walls then have steel and wood beams supporting the house. Treated plywood and lumber can be used in constructing the joists and ceilings of the basement. Many times basements are finished into usable living space allowing a home’s living space to be expanded without having to build onto the existing structure. If a basement is not sealed...

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Slab foundations and crawlspaces are two of the most ideal types of home foundation, especially if you live in a place that has a warm climate. To determine which of these two will best suit your home, consider factors like the type of soil, frost line, depth of water tables, slope, and even water drainage in the area where you will build your house. Take into account the building codes in your state or locality. Here’s a basic comparison of these two types of foundation to help you decide which one is appropriate for your home.??

Slab Foundation?

?This type of foundation is created using and 8-inch thick concrete slab. The slab is where the house will sit, while the utility and piping systems will be set underneath the slab. Installing drainage pipes and electrical wires should be done correctly because it will be hard to fix and repair such systems once the house has been constructed above the slab.??

One of the advantages of slab foundations is their low...

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The IECC energy code is part of the great International Building Code. It pretty much applies to all residential construction and its compliance is required just like the plumbing, electrical and structural codes.

I disagree that a well designed building should not be equated with minimum prescriptive R values (at least!!!) from the most recent IECC. The other compliance paths are good because of design flexibility but they introduce an abuse factor.

The alternatives are based on the prescriptive levels which are the intent of the code. In my experience, most designers will use the total UA path when making building envelope tradeoffs. I think using true simulated performance in most residential projects is rare and from my understanding, additions are not allowed to use it.

Alternative compliance is meant for innovation, creativity and unique design. You can skimp in certain areas and details but it MUST be made up for in others to obtain equal baseline...

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Crawl Spaces: The Downsides of Basements With Few of The Benefits

Bird's eye view

CRAWL SPACES ARE LIKE MINI BASEMENTS. If you don't need the subterranean living space, you can save money on excavation and foundation walls. Crawl spaces should be sealed, insulated, and passively kept warm if mechanical equipment, ducts and plumbing are left there. A crawl space is less likely to have moisture problems if the crawl space floor is higher than the exterior grade.

Crawl spaces should be insulated and sealed

Many building experts recommend against crawl spaces because they have the water problems of a basement with almost none of the storage space, at much higher cost than a slab.

Still, sometimes a crawl space makes sense. Crawl space walls should be insulated with rigid foam or closed-cell spray polyurethane foam, and should be sealed rather than vented.

Crawl spaces should be treated as if they were miniature basements, which is exactly...

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Until the 1970s, building a home usually meant beginning with a crawl space structure or a full basement where possible. Since then, however, concrete slab 1 foundations have become more popular. The decision of to build a home on a slab or over a conventional crawl space is not merely a matter of preference. Many factors go into making this “foundational” decision. With the information below, we strive to make the choice easier for you.

Geography and Climate Considerations

A crawl space works especially well on a sloped lot where the footers 2 can be designed to level the home’s flooring. This type is also preferable in areas prone to earthquakes since any shifting in the earth can permanently damage a concrete foundation. Soils like red clay almost always require the use of crawl spaces since they are not stable enough to support a cement slab.

Crawl space foundations are recommended for dryer climates since moisture can accumulate there, and they are also...

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Here in east Texas, we’re blessed with mild winters. Due to this, it’s rare for homes to be built with full basements. However, the old debate of “slab vs. crawl space” is alive and well. This article will look at the pros and cons of both types of foundations.

Slabs: the Good and the Bad

A slab is created by digging into the soil several inches, pouring in concrete, and reinforcing it with metal rods. The house is built directly on top.

This is a simple method of construction that allows house building to continue, without waiting days for footings or other foundation components to cure. Heating and air ducts are usually run through the attic, and the water heater and furnace are located in the home. Electric, sewage, and water lines run under the slab and enter the home at certain points.

Perhaps the biggest advantage of using a slab is cost. As much as $10,000 can be saved when building a slab vs. crawl space. This is especially true in areas...

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Summary: Which is better, a crawl space foundation or a concrete slab foundation, depends on several factors besides cost.

Carl,
Cost of 2800sq feet crawl space vs. concrete slab, which is best overall beyond cost?
Amos

Hi Amos,

Concrete slab foundations built on grade (level land) are easy to excavate and are installed quickly, speeding up the construction project. After all, when the slab is finished, you already have the 1st floor done and you are ready for wall framing in a day or so.

If the land is not level or the water tables are high, a raised slab foundation can be utilized.

But concrete slab foundations have their drawbacks. Slab foundations are considered by many as "cheap" and this can and will affect the homes' market (resale) value.

Concrete slab foundations are also hard on the human body, walking or standing. They are also cold.

Unless you install a radiant heat system in the concrete slab,...

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Give us a call today for a free home inspection and price estimate. We work with homeowners and businesses in Des Moines, Ames, Waterloo and all Central...

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Posted by : Ecohome | Emmanuel Cosgrove, Mike Reynolds

TECHNICAL GUIDE : Slab-On-Grade Construction, an affordable and durable alternative to starting a home with a basement.

Starting your home with a slab-on-grade instead of a conventional basement foundation can greatly reduce your environmental impact during construction, and has the potential to offer significant financial savings as well.

By replacing concrete with lower-impact and better performing building materials, you can eliminate many tons of greenhouse gas emissions from your building materials as well as during the future operation of the home.

Slab-on-grade construction is a somewhat uncommon method of home building that replaces the conventional foundation wall and basement with a concrete slab that rests directly on grade. The technique lends itself to most types of terrain, with the exception of heavily sloped sites.

New: check out our step-by-step video building guide starting...

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A correctly designed and properly installed foundation holds the weight of the house in place while insulating against the cold, keeping out moisture and resisting the movement of the surrounding earth. There are three basic types: a concrete slab on grade (least expensive); a crawl space foundation with short walls supporting the house; or a full basement foundation (most expensive) with 8'-10' walls. Which type is best for a specific location depends on soil and groundwater conditions. Typical costs:Foundation costs vary significantly by region. Other factors include the thickness and psi (pounds per square inch) rating of the concrete, and the type of steel reinforcement used. Clearing, grading the land and digging may be included or billed separately. See Land Clearing, Land Grading and Excavation.A slab foundation for an average 1,600- to 1,800-square-foot family home might cost about $7,000-$16,000 or more, while a slab foundation for a 3,000- to 4,500-square-foot home...
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