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Screw Type for Concrete Blocks

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  • Screw Type for Concrete Blocks

    I will be building a 6ft wide 12ft long roof extension to my daughter's concrete block storage shed next week. She currently keeps her lawn tractor inside along with some other items (grill, lawn wagon etc) but wants to move them to a roofed cover and use her shed for household storage. I have it designed and am ready for everything - but attaching the roofing support to the back side of the concrete block building. (BTW, the shed has a below ground storm cellar, that is why it was made of concrete blocks.)

    For attachment of the roof to the building, I will have a 12ft long pressure treated 2x4. I plan on using liquid nails but I know that I need to also anchor it with bolts somehow. What kind of screws can be used on concrete blocks without damaging the blocks. DO I need to drill and add anchors?

    To the 12ft board, I will attach 2x4 rafters 6ft long (pressure treated) at 16 inch intervals and Ondura 4-ft x 6.58-ft Corrugated Asphalt Roof Panels for the roof. Not too heavy. The outward side of the roof will have 5 4x4 posts for support.

    Your help an suggestions are appreciated.
    Hank Lee

    Experience is what you get when you don't get what you wanted!

  • #2
    On my previous job we used a lot of epoxy anchors in concrete, and Ive used my own version of it in concrete and wood. The problem you will have is the concrete blocks is their wall thickness, and the fact the walls are vertical. Not good for epoxy anchors. Epoxy anchors for vertical use has the consistency of bubble gum. I would suggest fastening your horizontal top plate to the CMU by carefully drilling through the CMU and top plate and inserting a length of 1/2 all thread rod and washer and nut on both ends. ( bolts would work but get rather expensive for this length) Buy your threaded rod in your box store electrical dept in 10 lengths.
    Fasten the rafters to the top plate with a Simpson strong tie top plate to rafter hurricane tie. I think these ties are quicker and easier than the conventional house builder method of toe nailing on both sides of the rafter.
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    Last edited by capncarl; 04-27-2018, 11:43 PM.


    • #3
      Thanks! Now my mind is going. Got it!
      Hank Lee

      Experience is what you get when you don't get what you wanted!


      • #4
        Leehjlp, I didnt catch that you were going to attach a shed roof, rather I thought attaching a roof to CMU walls. A Shed roof puts a lot of weight on the top plate so you definitely want to attach it securely. Like I suggested, the top plate, and Simpson hurricane ties but also use a 2x4 for a perch nailed or screwed under the hurricane tie to establish a rafter height and support. This perch is added after you get the outside plate mounted and leveled on your poles, a rafter held up in place on both ends or the roof where you are happy with the roof slope, then screwed through the hurricane tie. Then you jam the perch snug against the bottom of the rafter ( on top of the hurricane tie) and fasten it in place. This makes the remaining rafters a one man quick and easy job.

        I have a 14x48 shed roof attached to my shop eave board. The pre fab trusses were designed with reinforced eave board on one end especially for this purpose. Several years after the shop was built I added the shed. This was my work around the building covenants that limited my shop size during construction. I nailed the 2x8 top plate to the eave board and just for safety sake I screwed through both 2xs into each rafter with 8 long roofing screws. That ought to hold it! I had acquired enough 3/4 plywood decking to cover the whole roof for free! So I had to use it, so I used 2x8 rafters. A 3/4 piece of plywood is heavy and really hard to put on a roof single handed but you got to work with what you got. I had the roofing crew that roofed the house and shop roof the shed. I spray painted the underside of the shed roof. 5yrs later it needed repainting and I noticed it looked different...... the eave board had started coming off the eaves and had dropped down several inches. In the attic I found out why, the reinforced eave board side had been installed on the front of the shop rather than the back as I intended. Oops. Rather than tear the shed roof off and start over I elected to jack it up and support like it was an outside wall. Lots of work but way less than tearing it off and starting over again.
        Moral to this story? Make sure beyond a shadow of a doubt you attach a shed roof securely to your structure. If my roof had fallen it would have destroyed a boat and my truck.

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        • #5
          I've always used expandable type anchors, in which you drill a hole to fit the expandable insert. When you screw the bolt into the anchor, it expands and grips the inside of the hole, forming a very tight lock and does not damage the block or concrete wall.

          Pretty simple to install, as you drill a hole in the block with a masonary bit, insert the anchor and simply bolt into it.

          I used this type of anchor when I attached the deck to my Painted Post house some twenty-plus years ago and everything is still rock solid. (I'm sure my 25 x 14 ft deck has had a lot more stress on it than your roof will receive.)

          Here's a link to the type of anchor I refer to (not necessarily the brand though, as I don't remember that).

          Hope this helps,

          Think it Through Before You Do!


          • #6
            Thanks for the ideas. CapnCarl, I most certainly will use the Simpson Ties, and screws too. CWS, Thanks for the info.

            My daughter has a Lowes close by and the HD is about 20 miles away. I will wait until I get there to pick the particular parts. This gives me some extra things to think about.
            Hank Lee

            Experience is what you get when you don't get what you wanted!


            • #7
              One of the things Im not that pleased with when using the galvanized stud hangers and various connectors, not just Simpson but all brands, is nailing the stud at its end causes it to split, That lessens the effectiveness of being able to hold really good. Granted it will still hold a lot better than the conventional being toe nailed.
              i wish these hangers offered a wider area to attach the studs or rafter.


              • cwsmith
                cwsmith commented
                Editing a comment
                I agree Carl. There are places for nail and places for screw and bolts. Not sure if I was always true to such things, as I've certainly learned along the way, but to me, it's about structure and strength, more than speed and efficiency. Using the right hardware is essential to longevity.


            • #8
              Polyurethane concrete adhesive like PL500 is VERY effective. So are Redhead screws.