DUROCK Cement Board for Exterior Walls

Discussion in 'Remodel Forum & Blog' started by MAD King, Dec 25, 2013.

  1. MAD King

    MAD King New Member

    Messages:
    47
    Location:
    Nashville, TN
    Hello,

    can I use the cement boards for the exterior walls?
    I would like to replace the vinyl siding and the plywood underneath with the cement board.
    I read a little bit that it is possible, but not on how it is done right.
    Anyone with good advices?

    Thank you
  2. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,180
    Location:
    New England
    At least some of the cbu manufacturers (James Hardie for one) make cement based exterior siding...I'm not sure about Durock. On some, you can get it prepainted, or in a primer. Also comes in various styles and panel sizes. Over the years, some of them have had issues, but much of that falls back to not following the instructions to the letter (critical on this type of install).
  3. MAD King

    MAD King New Member

    Messages:
    47
    Location:
    Nashville, TN
    Thank you for your reply.
    I know about the cement sidings, but I do not like the look of it.
    That's why I would like to have the cement board and on top some stucco.
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,180
    Location:
    New England
    I do not think any of the cbu boards are suitable as a structural panel (i.e., say in place of plywood for the cladding)...they are only a compatibility layer for mortar based materials. For wind load, earthquakes, and similar loading, the cbu cannot be used alone - ply, or a similarly rated material must be there to prevent racking and as a resilient panel that holds things together. Cbu would crumble around the fasteners if it were required to be a load bearing panel under those circumstances and then not provide the structural strength required.
  5. MAD King

    MAD King New Member

    Messages:
    47
    Location:
    Nashville, TN
    But aren't the panels made from the same material?
  6. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,495
    Location:
    North Vancouver, BC
    Durock from what little I have seen of it is a crappy board.

    Wonderboard Panels look much better.

    Hardi Backer Panels not approved for outdoors.

    You will want drainage, a rain screen, a scratch coat, a brown coat and a top coat.
  7. MAD King

    MAD King New Member

    Messages:
    47
    Location:
    Nashville, TN
  8. Dana

    Dana In the trades

    Messages:
    2,930
    Location:
    01609
    Not all fiber cement backer-boards are rated for exterior use- many will fall apart from freeze/thaw cycles in short years in a Nashville TN climate.

    If you are going for stucco, you need at least a 1/4" ventilation gap (3/4" is better) between the stucco and any sheathing or the moisture drives during the summer will rot your finish wall. If wood sheathing, you'll need a ~0.6-2 perm vapor retarder (double-layered #15 felt is the classic) on the vent-gap side of the sheathing.
  9. johnfrwhipple

    johnfrwhipple Bathroom Design & Build - North Vancouver, B.C.

    Messages:
    4,495
    Location:
    North Vancouver, BC
    I worked with both boards this month. Love Wonder Board - hate Durock.

    Found the Durock, dry, brittle and very weak at the surface layer.

    Don't think a cement backer board is your answer.

    Look up Rain Screens and go at the process with a more traditional install.

    Stucc is a funny beast. Lots of variations you can try.

    Do you have a local stucco supply yard? They have many products designed to make life easier for you.
  10. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    22,180
    Location:
    New England
    Fiber cement siding is applied over the structural wall sheathing, it is for appearance and waterproofing, not structural purposes. While an interior wall may add some structural strength, and cbu may be used there, just like drywall, it is not structural from the external viewpoint.
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