Three tips for choosing the right material for your project
- CONFIRM LONG-TERM THERMAL PERFORMANCE. Two of the rigid foam insulations most commonly used below grade and under slabs are expanded polystyrene (EPS) and extruded polystyrene (XPS).
- ENSURE MINIMAL LONG-TERM MOISTURE ABSORPTION. In addition to R-value stability, rigid foam insulations differ in their rates of moisture absorption and their ability to dry.
- TARGET AN APPROPRIATE COMPRESSIVE STRENGTH. One of the best ways to save money on rigid foam insulation installed under concrete slabs is to ensure the material is not over-engineered.
- CONCLUSION. With building owners’ growing desire to save money on heating and cooling costs, and increasingly stringent energy codes, contractors will be installing below-grade and under-slab insulation on more of ...
What kind of foam do you use under concrete slab?
- Drill at least four holes through the slab at a point that's centered on the void beneath.
- Connect a hose to a slabjacking pump, then run the hose to the holes leading to the void.
- Mix the fill material in a wheelbarrow, using a spade.
- Fill the pump with the fill material and set it to a pressure of 10 psi.
How do you fasten a 2x4 to a concrete slab?
- Cut nails (aka masonry nails)
- Concrete nails
- Concrete screws
- Wedge anchors
- Construction Adhesive
What are the problems in using foam concrete?
Workmanship problems:
- Not properly supporting the forms when the concrete is poured, often from being in a rush or to save costs. ...
- Common large voids left under window or door sill plates. ...
- Many builders use the wrong recommended aggregate size and slump by the manufacturer of the ICF forms which contributes to many problems.
Which cement is good for slab?
- PPC is normal cement avaliable in market which gives minimum compressive strength of 33 (Mpa or N/mm2) on 28 days of curing.
- This cement is suitable for normal construction works.
- This cement concrete requires normal curing as heat of hydration is lower.
- Initial strength is low but final strength is similar to that of OPC 33
Should you put foam under concrete slab?
Putting rigid insulation under the concrete slab is a great way to ensure that your new space will be energy-efficient for as long as it stands! It's required for many new structures to meet code, and it can also protect the concrete from water damage.
How thick should foam be under concrete slab?
Because concrete is solid, heat or air won't escape as easily as other floors. Therefore, when adding insulation, keep it at least two inches thick, depending on the type of insulation you use.
What is the best material to put under concrete slab?
Most concrete contractors want a mix of coarse and fine aggregate to create a compactable base that is going to be safe for settlement and drainage. Crusher run (a mix of crushed stone and stone dust) is one of the best base materials for concrete flatwork.
What is the best base under concrete?
What is the Best Base for a Concrete Slab? Most people build a driveway or a patio so in that case, a good choice would be a mix of coarse and fine aggregate which will create a compactable base. Overall, a mix of crushed stone and stone dust is the best base material for any concrete flatwork.
Why do they put Styrofoam under concrete?
They reduce the effects of soil movement, decrease the amount of concrete required, and have thermal insular properties making them a cost effective component for any home, building or complex.
Will Great Stuff foam lift concrete?
0:063:01Lifting Concrete with Spray Foam - YouTubeYouTubeStart of suggested clipEnd of suggested clipThis foam can rise and restore uneven pavement to a stable and elevated surface the foam naturallyMoreThis foam can rise and restore uneven pavement to a stable and elevated surface the foam naturally fills any air pockets that it finds. This means that it can give pavement a nice even lift.
Do you need rebar for 4 inch slab?
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. For concrete that is 5–6 inches thick, rebar is suggested. The thicker the slab, the more durable it will be.
How do you prepare the ground for a concrete slab?
2:176:18Pouring a concrete slab: Prepare the Ground & Drainage - YouTubeYouTubeStart of suggested clipEnd of suggested clipThe first thing you want to do is bring in a backhoe or a skip loader and scrape off any organicMoreThe first thing you want to do is bring in a backhoe or a skip loader and scrape off any organic material or topsoil from the area where the slab will be poured topsoil.
Can I pour concrete directly on dirt?
Long story short, yes you can pour concrete over dirt.
Do I need a sub-base for a concrete slab?
Subbase for Concrete Slab The subbase placement is optional and it serves as a work platform for construction of the slab and provide more uniform support for the slab.
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. Without crushed stone, pooling water will settle under it and erode your slab. Adding a layer of crushed stone will add proper drainage, as well as create a barrier between your slab and the ground.
Can I pour concrete over gravel?
Cement mix might work in some cases over an existing gravel driveway. Laying a concrete driveway over an existing gravel one is possible, but it is not generally recommended. The kind of gravel that is intended to go under cement is typically a smaller grade than what is used for gravel driveways.
What kind of foam is used to lift concrete?
Polyurethane foam is strong and permanent. It is used in many major commercial projects to lift and stabilize extremely heavy structures and surfaces with much heavier traffic than residential concrete, including roads, bridges and industrial buildings.
How much does it cost to raise concrete with foam?
Mudjacking costs $3 to $6 per square foot, and foam jacking is $5 to $25 per square foot. The average cost of slabjacking to raise a concrete slab is between $511 and $1,790, with most spending $830. Mudjacking Cost.
Can you use spray foam under concrete slab?
Insulating under foundation and basement slabs using SPF ( spray polyurethane foam ) offers certain advantages over the more common method of using rigid foam board. Only closed-cell SPF can be used in a subslab installation; the open-cell foam does not have adequate compressive strength.
How do you fix a sunken concrete slab?
The least expensive way to raise a sunken slab is to inject a combination of dirt, aggregate and Portland cement through holes in the surface. This process is called mud jacking, and it’s a job best left to pros with the equipment to do it, because the material has to be injected under pressure to do the job.
Does expanding foam set hard?
Nearly everyone has heard of expanding foam, or “expandy foam ” as I call it. It has a long tube that screws on to the top, and when you squirt it out, it usually looks like a thick, solid yellowish foam that expands over time as it dries and hardens.
Do it yourself foam jacking?
So, how do you raise a concrete slab with foam? Locate the dips, Get the right equipment and fo am., use 5/8-inch masonry bit to drill a hole through the concrete, and spray the foam into it. The foam will expand and harden, filling the void in the ground and leveling the driveway.
How long does concrete jacking last?
In fact, most homeowners report that their repairs last about 8 to 10 years.
What Kind of Insulation Goes Under Concrete Slab?
Compressive strength – the amount of weight the foam panels can support – is an important determining factor in under-grade insulation. The insulation used under a slab needs to meet strength requirements, or else it can slowly collapse under the weight, destroying the foundation of the home. Compressive strength is measured in PSI and refers to how many pounds one square inch of the insulation can support.
How much insulation should I use for a concrete slab?
ASTM standards dictate a minimum of 10 PSI for under slab rigid insulation, and 15 is the most common.
Do You Need a Vapor Barrier Under a Concrete Slab?
A vapor barrier is an essential part of a good slab foundation. Since water from the soil soaks into the rigid insulation over time, it’s necessary to put a barrier between the foam and the concrete. In the past, 6-mi (6/1000”) vapor barriers were quite common, but the American Concrete Institute now states that a vapor barrier should never be less than 10-mi (10/1000”) thick.
Can You Use Spray Foam Under Concrete Slab?
However, you must make sure that 2-pound closed-cell SPF is being used; any other type of sprayable foam won’t be dense enough to support the slab.
Why put insulation under concrete?
Putting rigid insulation under the concrete slab is a great way to ensure that your new space will be energy-efficient for as long as it stands! It’s required for many new structures to meet code, and it can also protect the concrete from water damage. To ensure that the foundation of your home isn’t a major source of heat loss, ...
How thick should a vapor barrier be?
In the past, 6-mi (6/1000”) vapor barriers were quite common, but the American Concrete Institute now states that a vapor barrier should never be less than 10-mi (10/1000”) thick. Polyethylene material isn’t totally waterproof, so it isn’t just the thickness of the vapor barrier that matters.
What is the R value of concrete?
R-value is one of the most important specifications of under-grade insulation. R-value describes a material’s ability to resist heat transfer. The higher the R-value, the better it insulates. A 4-inch concrete slab has an R-value of 0.4, which is very low; heat escapes through concrete very easily.
What type of insulation is used for concrete slabs?
The most common types of under slab or concrete insulation include rigid foam insulations, such as expanded polystyrene (EPS), extruded polystyrene (XPS) and radiant insulation, such as Prodex.
What is the best under slab insulation?
Our expert recommendation for the best under slab insulation is Prodex. It’s a new-generation radiant floor insulation that meets all of the challenges of under slab insulation. It blocks cold, heat, moisture, mold and unwelcome creatures.
How many rolls of under concrete tape?
Under concrete tape comes in flexible packages of two or 24 rolls. The two rolls will serve 1,250 sq ft of insulation while the 24 rolls will be sufficient for 15,000 sq ft of insulation.
Why add a non-permeable membrane around the perimeter?
Add a non-permeable membrane around the entire perimeter to prevent insect infestation.
Why is concrete more conductive than other materials?
Because concrete has the ability to hold heat and is more conductive compared to other building materials, like wood for example.
Can you lose heat through slabs?
Depending on climate conditions in your region, your home can lose heat and cold through the building slabs.
What is the best insulation for under slabs?
Two of the rigid foam insulations most commonly used below grade and under slabs are expanded polystyrene (EPS) and extruded polystyrene (XPS). Although both are closed cell insulations, they perform very differently over the long term.
How to save money on insulation?
One of the best ways to save money on rigid foam insulation installed under concrete slabs is to ensure the material is not over-engineered. A common design assumption leads to specification of rigid foam strengths that are many orders of magnitude higher than necessary, which can double the insulation material cost.#N#Without getting into extensive technical details and mathematical formulas, the problem is engineers often use an overly conservative approach for insulation under concrete slabs. Many designers assume that point loads applied to a slab, such as those from the wheels of a forklift, transfer to the insulation in a triangular load path. Yet, concrete slabs distribute loads more uniformly than this, which means the insulation does not need as high of a compressive resistance as when one assumes a concentrated triangular load path.#N#An overly conservative design approach often results in specification of a high compressive resistance XPS product, when a more cost-effective EPS would offer sufficient strength. Since XPS typically costs more per inch than EPS, this is wasted money that comes off the contractor’s bottom line.#N#A simple solution for contractors is to ask the designers if they are using a formula from the Theory of Plates on Elastic Foundations, which take into account how slabs and insulation behave together. A resource to point them to for example calculations is the article “Right-sizing Under-slab Insulation,” in the April 2014 issue of Structure magazine.
Does rigid foam insulation degrade over time?
In addition to R-value stability, rigid foam insulations differ in their rates of moisture absorption and their ability to dry. Wetted insulation provides lower thermal resistance and can degrade over time. Since insulation installed below grade frequently contacts wetted soil, rates of moisture absorption and the ability to dry is key in these applications.
What is rigid foam?
Rigid foam is different from the insulating foam you would use in your walls. Foam for subfloors is much sturdier and can be walked on without risking cracks or breaking. It is ideal for placing on top of gravel foundations and withstanding concrete pours.
Why Do You Need Gravel Under a Concrete?
Even the most solid, compacted soil can shift dramatically with the weather changes, which will undermine your slab and cause cracks .
Can You Pour Concrete Over Dirt?
Yes, you can pour concrete over dirt. If you have a very compact soil-type, such as solid clay, then you may have ground that is solid enough to support a slab over a period of time.
Do I Need Foam Beneath a Concrete Slab, Patio, or Footing?
No, but it’s a good idea because it will seriously negate any cracking or shifting between seasons. The flexibility of the rigid insulation has “give” allowing it to absorb movement as the ground shifts and moves between seasons.
What is the best way to compact gravel?
When compacting gravel designated for a foundation of a concrete slab, it is best to use a machine. A plate compactor or jumping jack will compact the gravel in a fraction of the time that it would use to use a hand tamper.
Why is it important to compact concrete?
A level surface allows you to determine exactly how much concrete you’ll need. The most major benefit, though, is drainage. Water that seeps beneath a slab can erode soil, causing gaps between the earth and slab.
Does foam insulation work on concrete?
The foam will have a tremendous impact in terms of the insulation of your floor. If you intend to heat the space above your concrete slab, it is imperative you use fo am beneath the slab. As a barrier between the cold of the earth and the slab, it will help your slab retain heat much, much longer in the winter.
