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surface mounting in block walls

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  • surface mounting in block walls

    Got a couple of dozen switch and duplex metal boxes to surface mount on 5 inch solid block walls.
    What is the best method for anchoring these to the walls?
    Thanks,
    Chenchen.

  • #2
    Re: surface mounting in block walls

    I've always used atleast 2 plastic anchors per box in the most widely spaced holes provided in the box.Generally only used 4sq or 4 11/16 boxes as I hate using handi boxes and trying to stuff all the wire and device in that carefully.
    Sam

    Comment


    • #3
      Re: surface mounting in block walls

      If they really are solid and not hollow cinder blocks these should work well provided you carefully drill the pilot holes using their proper drill bit and don't over torque the screws. I use the standard hex head ones in the 3/16 x 1 or 1-1/2 size.

      http://www.concretescrews.com/

      I agree about that the little "Handy Box" are rather small. The deeper 2-1/8 deep 58371-1/2 handy boxes have enough room that when used for a duplex receptacle or SPST switch you should be fine. Trying to get a GFCI receptacle in one normally doesn't work and you need a 4" square box that's a minimum of 1-7/8 deep with proper cover. Most of the time for a SPST switch or Duplex (Residential or light commercial grade) the 1-7/8 deep handy boxes are fine 58361-1/2. Hospital or super industrial grade receptacles take a bit more room.
      Last edited by Woussko; 03-14-2008, 10:07 AM.

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      • #4
        Re: surface mounting in block walls

        you could let the electrician do this job,

        I would try the tapcons, screws, I have had good luck with them,

        which I believe the link that Woussko posted takes you to them, I like the hex head screw, over the Phillips,

        I think most of the building supply stores carry them now,
        Push sticks/blocks Save Fingers
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        • #5
          Re: surface mounting in block walls

          Tapcons are a good way to go and are incredibly strong. The hex heads are easier to drive and far less likely to strip than the phillips head. Use a 5/32" bit for 3/16" tapcons or a 3/16" bit for the 1/4" ones. If you use phillips type use a #2 point for the 3/16" screws and ONLY a #3 for the 1/4" screws. You almost certainly will strip them using the wrong tip.

          Comment


          • #6
            Re: surface mounting in block walls

            Originally posted by Woussko View Post
            If they really are solid and not hollow cinder blocks these should work well provided you carefully drill the pilot holes using their proper drill bit and don't over torque the screws.
            Doesn't matter if its hollow. Just use a length short enough so the threads don't go all the way past to the hollow part.

            Comment


            • #7
              Re: surface mounting in block walls

              I just installed outlets in my basement workshop. I used a hammer drill to drill the holes and then used plastic anchors and screws. Like others have mentioned, I used 4x4x2" boxes with plaster rings so I wouldn't need to struggle with packing in the 12 gage wire. Besides, using 12 gage wire, the little "handy boxes" didn't have enough volume to meet code. Be sure to use a grounding screw with the metal boxes.

              Comment


              • #8
                Re: surface mounting in block walls

                Thanks Guys,
                Looks like tapcons are the favorite; I'll give them a try.
                Another question...................
                Can you use regular gangable boxes for surface mounting; I know they are not as dressy as the rounded over ones but we have zillions of them on hand.
                Appearance is not an issue; they will be painted to match the walls and have SS covers.
                Chenchen.

                Comment


                • #9
                  Re: surface mounting in block walls

                  My own personal luck with tapcon screws hasn't been good at all so I never think of em.I know many people really like them and have good luck.If I ever get around to it I need to replace all the tapcons someone used on my iron fence thats attached to concrete fake bricks.Luckily it sits on the bricks too an the tapcons just keep it from falling over maybe 1 in 4 are actually holding in the fake bricks
                  Sam
                  Originally posted by Woussko View Post
                  If they really are solid and not hollow cinder blocks these should work well provided you carefully drill the pilot holes using their proper drill bit and don't over torque the screws. I use the standard hex head ones in the 3/16 x 1 or 1-1/2 size.

                  http://www.concretescrews.com/

                  I agree about that the little "Handy Box" are rather small. The deeper 2-1/8 deep 58371-1/2 handy boxes have enough room that when used for a duplex receptacle or SPST switch you should be fine. Trying to get a GFCI receptacle in one normally doesn't work and you need a 4" square box that's a minimum of 1-7/8 deep with proper cover. Most of the time for a SPST switch or Duplex (Residential or light commercial grade) the 1-7/8 deep handy boxes are fine 58361-1/2. Hospital or super industrial grade receptacles take a bit more room.

                  Comment


                  • #10
                    Re: surface mounting in block walls

                    Tapcon screws aren't for everything and you really do need to use their special drill bits and be sure the holes come out the proper size. Using a hammer drill in many cases results in the holes being oversizes and the threads stripping out. I have and use the plastic anchors myself in many cases. Try hard to get the ones with barb ridges so they don't just pull out on you. Use big screws and really force them to expand. You want to really mash the plastic into the masonry.

                    Comment


                    • #11
                      Re: surface mounting in block walls

                      Originally posted by threecreeks3 View Post
                      My own personal luck with tapcon screws hasn't been good at all so I never think of em.I know many people really like them and have good luck.If I ever get around to it I need to replace all the tapcons someone used on my iron fence thats attached to concrete fake bricks.Luckily it sits on the bricks too an the tapcons just keep it from falling over maybe 1 in 4 are actually holding in the fake bricks
                      Sam
                      Same here, I will only use Tapcons when nothing else is available. I have had more Tapcons strip out then I care to remember. I always use the supplied bit, and am careful to go straight in, but those things just strip out constantly. If you actually get one to get a good bite into the masonry, you have a strong connection, but I have had many, many that felt good to start, but work loose pretty quickly.

                      I prefer to use the plastic anchors also whenever I can.

                      Jeff

                      Comment


                      • #12
                        Re: surface mounting in block walls

                        Tapcons will go in very well once you get the knack for it. Since construction here is entirely concrete these things are pretty much the fastener of choice. I can set them with and almost perfect success rate. Out of the last fifty I've installed I've probably had one spin out due to a wallowed out hole and thats because I had to back it out after the first try. Using an impact driver also helps greatly at setting them with success.

                        I usually avoid the phillips head ones since the torque required to set them is really not suitable for a phillips head. If it must be phillips then I only use the 1/4" taps that use a #3 head. The larger #3 tip is far more difficult to strip and a lot less likely to jump off the slot when setting it. Almost every single stripped head I see is because a #2 tip was used. Thats a guarranteed way to strip it and the number one reason I see for people complaining they strip out easily.

                        As far as the drill bit, there's nothing special about the one provided in the combo packs. It's just a regular 5/32" or 3/16" (depending on the screw size) masonry bit of average quality. Use quality masonry bits like Dewalt or Bosch which will make a clean hole of the right size with less effort. Cheapo bits are a lot more likely to wallow out the holes since the user will force them around more when drilling. Another thing I find is rotary hammers are not always the ideal tool to drill the hole unless the concrete is hard enough a hammer drill will not be able to make it easily. The hole needs to be just the right size and the impact blast from a roto hammer is strong enough to just oversize the hole enough to compromise the holding strength of the screw. I always try the hammer drill first. In the other extreme, when the concrete is way too hard then a roto hammer is the weapon of choice. Struggling with hammer drill in that situation, the user will tend to lean into the drill hard forcing the bit to wobble around and flex wallowing out the hole.

                        Once installed right they offer one of the strongest methods of fastening anything to concrete. It's about comparable to an epoxy bond. Far superior to rubber anchors.

                        Comment


                        • #13
                          Re: surface mounting in block walls

                          Another thing that will keep your boxes hanging forever is hammer pins, or sometime called drive pins. I prefer them to tapcons and plastic anchors in most cases.

                          Comment


                          • #14
                            Re: surface mounting in block walls

                            O.K. Guys,
                            The design is finally done and thanks for all the info.
                            We are going with 3/4 emt and 4x4 boxes everywhere.
                            Maybe you can help with box reccommendations and covers in particular.
                            No wiring devices bought yet.
                            We have both single and double outlets and switches, a few single GFCI's, some ceiling boxes needed and exterior light mounts and a couple of weatherproof duplexes.
                            Any help will be appreciated on selections.
                            Chenchen.

                            Comment


                            • #15
                              Re: surface mounting in block walls

                              Please do this and you'll have loads of good info.

                              http://www.mulberrymetal.com/catalogc.pdf

                              Click on the left side tab "Box Covers and Conduit Bodies".

                              Now look in the lower right and right click on "Catalog" and download the .PDF file. Once done open it with Adobe Acrobat Reader and you're set. You'll need to work through the pages until you find the right covers. They are on pages C10 and C11 in the catalog.

                              Are you sure you really want to use 3/4 EMT? Normally 1/2 EMT is more than large enough. If you think you may want a 50 Amp receptacle for a welder or such, then I can see it. In that case you should look into 4-11/16 deep surface boxes too. For the normal stuff, I really can't see a need for 3/4 EMT. You can pull (4) #10 type THHN wires through 1/2 EMT just fine and I bet in many cases you'll only need (3) #12 wires.

                              As for the 4 x 4 boxes, I recommend looking at RACO #190, 191 and 192. A good electrical supply house should have one if not all of them in stock. Ask to see them before buying. There are some differences regarding knock-outs on them. The #185 is too shallow and ends up being a PITA product for most users.

                              Additionally I recommend downloading and printing out this part of the RACO catalog. It's another .PDF Adobe Acrobat file.
                              http://www.hubbellonline.com/wiring/...a_steelbox.pdf

                              If anyone needs the FREE Acrobat Reader, you may download it here.
                              http://www.adobe.com/products/acroba..._dl_get_reader

                              Please note that I've had problems with Firefox browser on the Hubbell-Raco web site and thus recommend using Internet Explorer which seems to work fine.
                              Last edited by Woussko; 03-27-2008, 03:14 PM.

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