The Dirt on Below-Grade Insulation – Insulfoam
It also discusses installation procedures for below-grade and under-slab insulation. Rigid foam insulation. Two common rigid foam insulations specified for below-grade applications are expanded polystyrene (EPS) and extruded polystyrene (XPS). EPS. An easy way to recognize EPS on the jobsite is that it is commonly white.
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Should vapor barrier in slab be under 4 in. of gravel or on top of
2-part question: 1) I'm building a 2-car garage with upstairs apartment in zone 4, 26′ x 28′. getting different opinions on whether the vapor barrier -6ml plastic- should be under the 4" of gravel or on top of the gravel directly under slab? Some are saying it is not good to pour concrete right on plastic, although this seems to be the ...
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Slab on Grade or Grade Slab | Types | Construction procedure
2. Monolithic Slab on Grade. Supported Slab on Grade / Grade Slab: Supported grade slab or slab on grade foundation is chosen when the traditional footings are already framed on site to raise the columns. From the below fig, it is clear that the wall stands on a footing and The grade slab is resting on a layer of gravel and moisture barrier.
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Crush and Run Instead of Gravel Under Slab
Malcolm, I had assumed 4" was sufficient. If it needs 6", I will comply, but at $675 per 22ton load, it hurts. :) Also, when you say - [top dress the 6" below the slab with a drainable fill] - you are talking about the 3/4" gravel between the ground and the concrete, or in my case between the ground and Fomular 250 25 psi foam and then concrete.
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Gravel under concrete slab? is it absolutely required?
What happens if you don't put gravel under concrete? Because concrete is a very porous material, it will absorb any moisture that it contacts. This can cause pooling. ... No, rebar is not required for a 4-inch slab of concrete on grade. A 4-inch-thick slab cast on the ground and in constant touch with it will float, with no need for rebar ...
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Q&A: Frostproof Slab-on-Grade | JLC Online
To adequately drain a slab, you need lots of compacted gravel below the slab, with sloping drains that lead to daylight. Gravel must be placed under the entire slab, extending below frost depth in an unheated building. You don't want one part of the slab pinned to the ledge, while other areas float on the gravel bed.
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why sand under concrete?
Here in Southern Calif. where there is hard clay dirt, sand will give tree roots a easy time, so it can pop up the patio or sidewalk. Sand on top of visqueen help remove the water in concrete so it sets faster. Sand does provide a homogeneous surface so the concrete will cure evenly (not crack).
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Should vapor barrier go above or below gravel? (2024)
However, the current practice recommended by the American Concrete Institute is to apply a heavy-grade, non-penetrable vapor barrier (or retarder) with the lowest possible permeance for the application over a layer of granular fill (crushed rock, gravel, etc.). The concrete slab is then poured on top of it.
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Sand or Gravel Under Concrete Slab? Let's End the Debate!
Gravel is required beneath a concrete slab. Gravel, which may be compacted, provides a solid base for your concrete. The driveway's base may need to be 4 to 12 inches deep, depending on its purpose. Most driveways should have a minimum of 6 inches of crushed stone or gravel. Let's dive into the discussion to clear all of your doubts.
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Curling of Slab Over Vapor Barrier
A.: A slab on grade deflects upward because of a variation in moisture content throughout the thickness. This is the result of more rapid drying from the top than the bottom. The drier top therefore shrinks faster than the bottom, causing curling. When there is a vapor barrier directly under the concrete it creates a greater difference in ...
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A Slab-On-Grade Foundation for Cold Climates
Proper drainage (lots of gravel) is the key. Synopsis: This article describes the construction of a slab-on-grade foundation that is capable of resisting the severe temperatures of northern climates. A thick layer of compacted gravel plus rigid-board insulation are two of the author's secrets for this low-cost alternative to full basement walls.
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Why Put Gravel Under Concrete?
What happens if you don't put gravel under concrete? Because concrete is a very porous material, it will absorb any moisture that it contacts. This can. ... No, you do not need rebar for a 4–inch slab of concrete on grade. A 4–inch-thick slab cast on the ground and in permanent contact with it will float and rebar is not required.
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What Type of Gravel Under Concrete Slab Is Best To …
Why Do You Need Gravel Under a Concrete Slab? Adding a gravel foundation may seem unnecessary, considering the strength of concrete. However, this process is crucial for maintaining the structural …
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Subgrades and Subbases for Slabs
The subbase, according to ACI 302.1, "Guide to Concrete Floor and Slab Construction," is a layer on top of the subgrade of "compactible, easy to trim, granular fill that will remain stable and …
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Why You Should Place Rocks Under Your Concrete Slabs And …
Eric. //. Concerts. There are many benefits to placing rocks under concrete slabs and footings. The rocks help to improve drainage and prevent soil erosion. They also add stability to the structure and help to resist wind and seismic forces. In addition, rocks can help to insulate the ground and keep the concrete from freezing in cold weather.
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Gravel vs. Sand Substrate for Sub-Slab Rigid Foam
Im doing a slab on grade with: 2″ foam insulation + 15mil vapor barrier and wire mash. For the base my excavation guy put compact sand but I been reading that most use gravel or 3/4 crushed rock. Are there any disadvantages of putting the foam directly on top of compacted sand vs gravel ? Im in a colder area by the way. Vermont
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Q&A: Frostproof Slab-on-Grade | JLC Online
This could be challenging under a slab connected to ledge, since groundwater often follows the contour of ledge. To adequately drain a slab, you need lots of …
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4+ Reasons Why You Need the Right Size Gravel …
To Get a Leveled Surface When preparing to lay concrete for your driveway, patio, or any other structure you are building, you must use the correct size gravel to ensure a level surface. Different types of …
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YES! You Need Gravel Under Concrete: Here's Why and How Much
Using gravel for a base under concrete is important for several reasons, which contribute to the overall durability, stability, and longevity of the concrete structure. Here are some key reasons why gravel is essential: 1. Improved drainage: Gravel serves as a permeable layer that allows water to drain …
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Proper Subgrade Prep| Concrete Construction Magazine
With slab-on-grade foundations, an alternative to native soil material may be used to restore grade. These imported fills may include granular materials such as sand, gravel, or crushed stone. These high …
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Understanding Gravel Size Under Concrete Slab: A Guide
When properly installed, gravel acts as a solid foundation, improving drainage, distributing weight evenly, providing stability, and protecting against frost …
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Concrete Vapor Barriers: The Pros & Cons of Getting The Vapors
The American Concrete Institute states that a vapor retarder should be placed directly under a concrete slab on grade if now, or in the future, a low permeable membrane (floor finish) will be installed upon the slab. Personally, I would follow their guidance. Thanks, Jason. ... We excavated the old floor and dirt put in a layer of gravel ...
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Should I Use Sand or Gravel Under a Concrete Slab?
You should put gravel that is 3/4 to 1 inch under a concrete slab. However, depending on the project, local building codes may dictate the proper gravel size and shape. Some concrete slabs that do not hold significant weight may have a subbase of sand. Also, keep in mind that the subbase you choose will affect the cost of your concrete patio ...
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Compact Fill Under Slab
If un-compacted, or poorly compacted, soil or fill sinks under a slab you end up with a hollow spot. If you drive on this concrete and apply pressure to it, the concrete tries to bend or stretch to conform to the hollow spot. The result is almost always a crack and the concrete slab drops down. I see photos of this unnecessary damage all the time.
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Capillary Break Beneath Slab
Pour the concrete slab directly over the polyethylene (see Figures 5, 6, and 7) or install rigid foam and then pour the concrete slab (see Figure 4). Figure 4 - Polyethylene sheeting works with the gravel as a capillary break under the slab and serves as a capillary break between the footing and the stem wall to prevent wicking of water from ...
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SLAB-ON-GRADE UNDERLAYMENT LITERATURE …
This section states that a 4-inch-thick base course of clean graded sand, gravel, crushed stone or crushed blast-furnace slag passing a 2-inch sieve shall be placed on the prepared subgrade when the slab is below grade. The Portland Cement Association (PCA) EB001.13T, Design and Control of Concrete Mixtures.
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Often asked: Why Put Gravel Under Concrete?
A concrete vapor barrier is any material that prevents moisture from entering a concrete slab. Vapor barriers are used because while fresh concrete is poured wet, it's not supposed to stay that way. It needs to dry and then stay dry to avoid flooring problems. This is why a vapor barrier under concrete is essential.
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Gravel under Concrete Slab | Pilots of America
If you pour four inches of concrete, place control cuts every 12' or less. Rebar, wire mesh, fiber mesh, et al is also dependent upon soil types, moisture content, environmental extremes. Again, concrete will crack. The metal will hold it all together and keep it from separating vertically.
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Proper Placement of Vapor Barriers
It is also possible that too much water or cement paste would be absorbed from the concrete by the sand, but probably not under most circumstances. ACI 302.1R-11 "Guide for Concrete Floor and Slab Construction," doesn't advocate universal use of vapor barriers but does make recommendations for their proper use. This guide says, in …
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Best Fill Under Concrete Slabs
Energy Efficient Building Network. The only layer that is absolutely required is the subgrade—you have to have ground to place a slab on ground on top of. If the …
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