Concrete Floor Insulation Requirements Construction Essay

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Is your basement or garage exceptionally chilly? An uninsulated concrete floor may be a large part of the problem. Insulating a concrete floor can save you money on your heating bill, making your garage or basement warmer and, by extension, the rest of your house.

In addition to offering insulation and energy savings, the plywood subfloor described here can provide the perfect foundation for finish flooring such as carpeting, adding warmth in look as well as in feel. 

To prepare for insulating the floor, first evaluate the condition of the concrete. If you know you have issues with moisture, tend to those problems before installing the insulation. Also, check the floor for smoothness and level; you may need to grind down significantly high spots to ensure an even surface.

Measure the distance between the slab and the ceiling; you must leave approximately 7 feet, 6 inches of clearance between theceiling and the surface of the finished floor to comply with building codes. The subfloor will take up about 2 inches, and any floor covering will also reduce your clearance, so plan accordingly. Finally, clean the surface of the slab thoroughly.

Next, unfurl 6-mil polyethylene sheeting over the floor to provide moisture protection. When laying the next row of sheeting, be sure to overlap the existing row by 6 inches, and then tape the seams. Adhere the edges of the polyethylene to the slab with caulking to prevent slippage.

Lay out pressure-treated 2-by-4 sleepers at the edges of the room. Abut their ends and fasten them to the slab with 2 1/4-inch masonry nails. Mark these perimeter sleepers for additional sleepers, which will be centered every 16 inches and laid out in one direction across the room.

Affix these additional sleepers to the slab, nailing at the end of each board and approximately every 4 feet thereafter. Check for level frequently as you go. Shims can be added where needed to ensure a level surface.

Fit 1 1/2-inch-thick rigid foam insulation between the sleepers; strips should be about 12 1/2 inches wide. Always measure for an exact fit so as not to compress the insulation, which can compromise its performance.

Place 3/4-inch plywood sheets across (not parallel to) the sleepers. Start alternate rows with half sheets to stagger the joints. Drive in 6d nails every 6 inches where the ends of the panels meet the sleeper supports and every 12 inches into sleepers under the panel centers.

Once the plywood surface is laid out, finish with the flooring material of your choice. (For more on insulating foundations, see the article on how to seal (caulk) around your home's foundation.)

hello all, this really doesnt pertain to my basement since we dont have one. but what we DO have is a house with concrete slab for our floor. the home used to be crawl space on one side and just slab on the other, we've been going through an extensive remodel and part of that was filling in the crawl space (60 tons of gravel with wheel barrows  ) and just pouring an entire new slab that covered the newly filled crawl space and the old slab. now, while plumbing, walls, electrical and so forth have taken priority its coming time soon to work on the flooring.

we intend to cover the slab with that laminate hardwood looking stuff but the winter here in PA has made me wonder if theres something i can do to help with the cold floors.

i was at home depot earlier this week and saw that pink styrofoam insulation comes in folded-up 3/8" thick 200 square foot bundles, while it has an r-value of only 1.5 i figured it would be better than nothing. from what i can tell the 3/8" plus the thickness of the laminate and the foam underlay stuff that goes under the laminate will just fall short of being a problem for floor clearance of the interior doors.

so i guess what i am askng is weather or not this is a good idea, or if anyone has a better solution.

thanks in advance for your time


Think of the surprise and delight a new homeowner would have to find that their basement is not only usable space, but warm and comfortable as well! By taking a few extra steps, builders can toss out the notion that basements are cursed to be dank, cold, musty storage rooms.

Most basements are built in direct contact with the cold moist ground. Concrete will absorb moisture, like a sponge, and the result is an uncomfortable, musty living space. The additional water introduced into the home can also lead to mold issues. Finding a way to keep water out of the basement will greatly improve the smell and health of the home.

Heat is also lost through the basement floor. The notion that heat always rises isn't entirely true. Heat will flow towards relatively cooler places. If ground under the home is cooler than the basement temperature, which is the case in almost every climate year round, heat will naturally try to escape through the concrete slab.

Creating an insulation layer and a vapor barrier between the concrete slab and the ground beneath it is the best practice in insulating basement floors. The insulation barrier will help keep warm air in, and the vapor barrier will keep unwanted moisture out.

Here's how to do it:

Evenly spread the base gravel under the basement slab, keeping it one inch lower than the conventional method.

Place a one-inch layer of 4'x8' extruded polystyrene foam board over the gravel, covering the entire floor area.

Tape the joints between the boards with builder's tape; you want to create a tight insulation layer.

Place 5 mil. polyethylene sheets over the foam board, overlapping at least 6 inches at the seam. Make sure there are no gaps, tears, or holes in the sheets and repair any you find with builder's tape. This covering will act as the vapor barrier.

Tape the joints with builder's tape and pour concrete as normal.

To go the extra mile, learn about insulating basement walls at

BuildIQ also offers a comprehensive online course on water management for foundations. More information can be found on their website.

And if you want to give homeowners some resources for understanding how insulation works, have them visit the DOE's "HYPERLINK ""Energy SaversHYPERLINK """ Website, which has fact sheets and information on insulation.

How to Insulate an Existing Concrete Floor

By Cameron Easey, eHow Contributor

updated: November 27, 2009

Existing concrete floors, like those found in most basements, can be cold if the floor has not been covered with carpet or insulated. If you plan to finish your basement or just want to provide a warmer floor, you can add a new sub-floor on top of the existing concrete. A new sub-floor can be constructed using rigid insulation and wood. Insulate existing concrete floors by first determining how much building material will be needed.

Difficulty: Moderate


Things You'll Need:

2-by-4 inch pressure-treated boards

Plywood sheeting

Power-actuated nail gun or ram set

Circular saw or miter saw

Polyethylene plastic

1-inch thick rigid foam insulation


Duct tape

Utility knife

Power drill





Remove all furniture from the floor so that it is completely clear. Clean up debris and dirt from the floor using a broom or a vacuum. Place polyethylene plastic sheets over the entire floor. Overlap the sheets by at least 3 inches. Place a strip of duct tape along the length of the seam. Cut the excess plastic with a utility knife.


Set pressure treated 2-by-4 inch boards along the perimeter of the basement flat side down. Use a tape measure to determine the lengths of 2-by-4 inch boards that will be needed. You can cut the 2-by-4 inch boards using a circular saw or miter saw.


Secure the 2-by-4 inch boards to the concrete floor using a power actuated nail gun or ram set. Place a nail every 2 feet along the boards.


Set and secure 2-by-4 boards, flat side down, to create a grid pattern within the 2-by-4 perimeter. Use the tape measure to determine the length needed for the boards.


Place rigid foam insulation within the grid you created with the 2-by-4 inch boards. Cut the insulation to size using a circular saw, if necessary.


Set plywood sheeting on top of the grid of 2-by-4 inch boards. Measure the plywood with a tape measure; cut it to the needed size with the circular saw, if necessary. Secure the plywood sheeting to the 2-by-4 boards with screws using a power drill.

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Tips & Warnings

Apply carpet or other type of covering if you want to finish the floor.

You can damage your ears if you do not wear ear protection when using a power actuated nail gun.

Read more: How to Insulate an Existing Concrete Floor |

Laying a concrete floor


Summary: Learn how to lay a concrete floor and how to mix and lay screed.

A concrete floor is usually laid during renovation work to replace a rotting timber floor. Before laying a concrete floor, you must consult your local Building Control Department as changing a floor can affect the ventilation in other parts of the building and it is possible that insulation will also be required. If infill material of more than 600mm is required a new suspended floor must be fitted instead, as the settlement of the infill material may result in damage to the new concrete floor.


Remove the skirting board, take up the old timber floor and joists and remove any doors.

Treat the ground and the walls below the old floor level with fungicide.

When removing the floor joists it is more than likely that recesses will be left in the wall. Fill them with bricks and mortar.

Measure and chalk a line around the room, using a spirit level, to mark the height of the new floor. Label this line A. This line marks the top of the screed. However, if you are planning to lay a thick floor covering on top of the new floor such as quarry tiles, allow for the depth of the tiles.

Measure down from line A 25mm and draw a line to mark the top of the concrete layer, and label this B.

From B measure down 100mm and mark this line C to indicate the top of the damp-proofing and insulation layer.

From C measure down 50mm and mark this line D - the top of the sand layer.

From D measure down another 50mm to mark the top of the hardcore layer which should be marked E.

From E measure down another 100mm to reach the base of your new concrete floor.

The total minimum depth required is 325mm from line A.



Before concreting you need to infill the area with layers of different materials.

The first layer is the hardcore, which can be rubble made up of old bricks or tiles, but break up any large pieces with a sledge hammer. Alternatively you can use coarse stone. Remove any wood, plaster or metal from the hardcore as it can have an unfavourable reaction with cement.

When you have reached level E, compact the hardcore with a compacting plate.

Cover the hardcore up to level D with a layer of sand, which should be tamped down and smoothed with the back of a shovel being moved in a circular motion.

Cut and lay a sheet of damp-proof membrane of 1,000 or 1,200 gauge thickness over the sand, ensuring that it also reaches up the wall to just below line A. If more than one sheet is required, overlap the sheets by 200mm (8in) and seal any joins with waterproof tape. Tape the membrane to the wall.

Lay the insulation board over the membrane, taping any joins.

Cut four lengths of insulation board to go around the walls. The lengths should be 100mm (4in) wide to reach line C, and will act as a mould for the concrete.


Laying the concrete

Mix up some concrete and fill the mould. The mix should be:

1 part cement

2 1/2 parts sand

4 parts aggregate

Don't add too much water as the mix needs to be quite stiff.

Starting at the wall furthest away from the door, shovel the concrete on to the floor area. Work across the floor area completing sections about 600mm at a time.

Use a length of 100mm x 50mm timber as a straight edge. Using the top of the insulation board at the sides of the room as a guide, scrape the straight edge forward to level the concrete.

Use a trowel to deposit concrete in any hollows. Once you have the concrete aligned with level C. Smooth the concrete with a plastering trowel.

Begin the next section and continue until the floor area is completed.

Cover the concrete with a polythene sheet to prevent rapid drying and possible shrinkage. Leave for a minimum of three days so the concrete sets.


Laying the screed

A screed (layer of mortar) should be laid over the concrete to produce a smooth surface. The floor screed mix should be:

3 parts sharp sand

1 part cement

Before laying the screed, dampen the concrete floor using water and a bonding agent mixed in equal parts.

Position two or three 38mm battens (depending on the width of the room) on the concrete running in the direction you are working. 

As you did when laying the concrete, work across the floor area completing sections about 600mm at a time. Layer the screed up to the level of the top of the battens.

Smooth the screed with a plastering trowel. When you are satisfied the screed is level remove the batten and fill in the gaps.

Smooth over the surface with a float.

Continue across the floor until the whole area is covered.

Cover with polythene sheets and leave to dry for one week. You can then fit skirting boards to cover the damp proof membrane visible above the surface of the floor.

The floor will take a few months to dry out completely. Do not lay an impermeable floor covering during this period.

Tricks That Save Time and Money

Posted on November 5, 2009 by admin

Here are useful tips learned during more than 40 years of installing epoxy urethane floor seals and coatings on Fortune 500 company concrete floors, as well as in basements, garages, and decks. These tips can help you avoid mistakes that can limit the life of your floor.

There are three broad steps to doing your floor project: planning and preparation, repairing, and applying the coating. This article is the third in a three part series, and deals with applying the epoxy paint to the floor.

General guidelines for applying an epoxy coating to your floor:

Do no harm. 

Investing in preparation produces the most years of service. 

Let the chemicals and equipment do the work. 

What can go wrong, will go wrong, unless you think ahead. 

Technique is what separates mortals from Rembrandts. 

An once of prevention is worth a pound of cure.

Now let's get started with tips on how to coat your floor with an epoxy or urethane floor paint.


Plan the job.

Good floor prep is key to a long lasting floor.

Take a break.

Mix 200 strokes.

Easy work makes for a better job

No one is perfect

Don't worry about tricks of gravity

A rag may not save you

Technique, technique, technique. 

This is an application pattern I like to teach and can serve you very well. Tip your roller and remove it quickly before it fills with liquid. Apply a quick wet line 3 or 4 feet back from where you had stopped coating. Now fill in the area between that wet line and your previous rolled area. As you overlap the new wet part, . The strong two-part coatings you are applying are not the water-based latexes that wipe easily off with a rag or a little water. If you get the coating on something you did not want to coat, it may be less harmful to leave it than to smear it all over the place. You may be better off chipping it off once it dries a little, or coating over it with paint that matches what you got it on. 

. As you put your first coat down, you will find things, bugs, sand, water, lint, and the like. What was in the air eventually will be on the floor. Remember this is a two-coat process. Yes, remove what you can as you go but those small bits of debris may be easier to remove when you screen between coats and sweep before your second coat. 

. I do floors lots of floors and still have misses, marks, and errors. I just can't rely on myself to be perfect all the time. That's why two coats are always planned. 

. Tape your cutting brush to a broom handle, use a wheeled bucket for 18-inch rollers, and several pails if using 9-inch rollers, and wear a mask if using solvent based products. Save your back and let yourself move quickly. Moving fast is more fun but it also sets a rhythm, which keeps a repetitive job interesting enough to maintain focus. 

Two-part flooring products can produce floors that click when you first walk over them. That clicking often means that the two parts were not mixed well. Clicking is sucking dust off your feet and could cause both lifting and discoloration problems down the road. Yes, the floor will usually stop clicking and harden, but it may come from aging rather than a strong chemical change. Mixing is not a science, but you must be able to count to 200. 

I always take a break after floor preparation to let the floor dry. Putting down a coating can be smooth and uniform or splotchy with misses. A little rest before the artistic part of the job will improve the quality of your application process. 

For this article, we will assume that you have done a good job of doing you're preparation and repair work already. 

Two-part coatings harden in the can once mixed, so it is best to have everything you need at the start of your job. A useful first step is to go to a website like www. concrete-floor-coatings. com for a free cost analysis report that also lists everything you need to do your job including step-by-step instructions. 

you re-wet your roller 

and as you overlap the previous area your roller is re-moistened. When you get to the end, roll back over the same area a second time. This re-rolling will spread any lines that may have come off your roller edges as you move across the floor.

Push the roller on, not off. 

I always flip my roller so that I move towards the open end. This little step pushes the roller onto the frame not off it. Each time the roller moves on the frame you have the danger of opening a gap at the end that fills the roller with coating as you dip. Soon you are getting lines as the liquid drips out of the ends of the roller. And soon the roller is sliding back and forth on your frame because the interior is now very slippery.

Don't hit the roller. 

If your roller cover starts to slide off the frame, don't tap the roller, tap the frame. If you tap the roller, you often get dents in the roller that show up as marks as you roll. If you tap the frame end of the roller, it will slide on without changing its shape.

There is dirt in that pail. 

I can't say how often I have compromised the quality of a job by pouring my last amount of coating out of the pail onto the floor as I exit. The problem is every piece of sand, lint, or bug that had stuck to the roller is resting at the bottom of the pail. Right where I have wanted the floor to look its best (at the entrance or exit), I have poured out all my debris on the floor so that I can use that last 3-oz. of coating. Don't do it! You will be sorry.

Screen the floor after your primer coat repairs are made

. By screening your floor with a 60 grit screen after any additional repairs are made, you can usually shave your floor flat. This screening removes bubbles, lint, sand, bugs, leaves, and fillers that are above the desired surface.

Sweep your floor with a kitchen type broom before coating. 

Push brooms just don't pick up enough of the small grains. A kitchen broom takes a little longer but does a better job.

Vacuum the corners

. It is just too hard to get grains of sand and other small particles out of corners and along baseboards or out of holes unless you use a vacuum.

How to Insulate a Concrete Floor

By Emily Patterson, eHow Contributor

updated: May 7, 2010

Insulating a concrete slab reduces heat loss and helps to moderate the temperature of a home, according to the U.S. Department of Energy. Solve moisture problems before insulating a concrete floor to avoid mold growth in or under the insulation. Install the insulation on a concrete floor before beginning work to finish a basement. The insulation will increase the comfort of the basement and save on overall heating costs.

Difficulty: Moderately Challenging


Things You'll Need:



Scrub brush

Foam board adhesive

Utility knife

Caulk gun

Interior rigid foam insulation

Vinyl tape

Drywall saw


Blanket or pad

Pressure treated 3/4-inch decking


Concrete nailer (if using concrete nails)

Concrete nails (if using concrete nails)

Drill (if using concrete screws)

Masonry drill bit (if using concrete screws)

Screwdriver bit for drill (if using concrete screws)

3/4-inch tongue and groove subfloor

1 1/4-inch stainless steel or exterior screws


Clean the concrete floor with a vacuum to remove all loose soil and debris. Remove stains and possible mold with hot soapy water and a scrub brush. Allow the floor to dry completely.


Cut the tip of the foam board adhesive at an angle with a utility knife. With the wire attachment on a caulk gun or a long nail, puncture the seal inside the tube of foam board adhesive. Insert the tube into a caulk gun.


Apply a bead of foam board adhesive to the back of the foam board (the side without a foil or plastic coating) around the perimeter of the insulation approximately 3 inches from the edge. Apply another bead of foam board adhesive in a zig-zag pattern across the center of the foam board insulation. Lay interior rigid foam insulation directly on the concrete floor with the foil side facing up. Do not walk on the foam insulation to avoid punctures or compressing the foam.


Tape the seams with vinyl tape. Place a small sheet of plywood on a blanket or pad when taping the seams to distribute your weight on the insulation.


Cut the rigid foam insulation with a drywall saw as needed to fit small pieces on the sides and around stationary fixtures, such as plumbing and heating units. Seal around the objects by taping half on the foam insulation and half on the object with vinyl tape.


Install pressure-treated strips across the foam board. Space them approximately every two feet, one on each end and two evenly spaced in the middle, on the foam board insulation. Secure with concrete nails or concrete screws. Concrete nails require the use of a concrete nailer. However, concrete screws require a drill and masonry bit to pre-drill the hole and then a screwdriver bit to secure the concrete screw into the pre-drilled hole. Select the masonry bit by the size of the concrete screws. The proper bit size will be printed on the screw package label.


Place sheets of 3/4-inch subfloor on top of the pressure treated strips. Secure to the strips with 1 1/4-inch stainless steel or exterior grade screws. Cut as needed to fit around objects such as heaters and plumbing.