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Green Basics

Concrete Block

Concrete Block Walls: Low Tech and Durable

A tried-and-true system

Concrete masonry units (CMUs) are the standard hollow concrete blocks; the product has been around for more than a century. CMU use is more common in the southeastern U.S. than in cold-weather regions. CMUs are resistant to fire and insects, and, with adequate steel reinforcement, also offer high wind resistance. Walls can be insulated on the inside or the outside.

Fluffier concrete

An only slightly younger cousin to CMUs are aerated autoclaved concrete (AAC) blocks. Sold under several brand names, AAC blocks are made with a mixture of portland cement, lime, silica sand, water, and aluminum powder. A reaction between the cement and aluminum creates tiny bubbles of hydrogen that increase the mixture’s volume fivefold.

BuildingScience.com:

Interior Insulation Retrofits of Load-Bearing Masonry Walls in Cold Climates

Concrete masonry units (CMUs) are the standard hollow concrete blocks; the product has been around for more than a century. CMU use is more common in the southeastern U.S. than in cold-weather regions. CMUs are resistant to fire and insects, and, with adequate steel reinforcement, also offer high wind resistance. Walls can be insulated on the inside or the outside.

An only slightly younger cousin to CMUs are aerated autoclaved concrete (AAC) blocks. Sold under several brand names, AAC blocks are made with …

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5 Comments

  1. Stephen Colley | | #1

    Autoclaved Concrete
    I would like to see more third party information and commentary regarding building with aerated autoclaved concrete (AAC). I designed a 2-story 2600sf house out of AAC almost ten years ago, and the owners are very happy with the decision to use it. I'm in a hot-humid climate. I'm assuming there's little on the subject primarily due to so few homes and businesses building with it.

  2. Doug Haisch | | #2

    Concrete block homes in Florida
    Can we glue 3/4" styform to the inside walls to increase the R value of the wall?
    Then finish with paneling or a laminatred panel to finish the wall. Now will the foil side of the styaform face the out side or inside?
    Thank you for reading any your suggestions

  3. User avater GBA Editor
    Martin Holladay | | #3

    Response to Doug
    Doug,
    Q. "Can we glue 3/4" styform to the inside walls to increase the R value of the wall?"

    A. Yes.

    Q. "Now will the foil side of the styrofoam face the outside or inside?"

    A. The foil facing will not provide any thermal benefit unless it faces an air space. If you glue one side to the concrete block, don't glue the side with the foil. Face the foil side toward the inside; then install wood strapping, 16 inches on center, on top of the foam. You can attach your drywall to the strapping.

  4. Simon Berry | | #4

    concrete block walls
    new user and learning techniques. Would anyone tell me that by doing solid conc block exterior wall to a garden building without a render or sealant be?? ok as long as we have dpc under concrete slab? The internal wall is going to be plaster board on timber frame with a mulitfoil insulation layer between the timber and internal walls. Do I need to leave a gap? Thank you in advance!

  5. User avater GBA Editor
    Martin Holladay | | #5

    Response to Simon Berry
    Simon,
    I don't know what "DPC" is, but I'm guessing it's polyethyhlene.

    If you are building a garden shed, it hardly matters how you build it. There won't be any heat or air conditioning, right?

    The main problem with an unplastered concrete-block wall is that it is ugly. If you don't mind looking at it, you'll be fine.

    Of course, this depends on having a roof with adequate overhangs so that the walls don't get too wet. What's your climate?

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