Reply To: Hanging a shelf
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I wouldn’t depend on any system that depends on fastening to the furring strips, which themselves are probably fastened with now rusty cut nails. And i’d Heed the advise that you avoid any system that cantilevers the screws unsupported.
So I’d use something like the TAPCON series of fasteners that are tailored for all different applications in concrete or cinder/cement block screwed through the furring strips into the block. Block walls are somewhat weaker than solid concrete and depend on the type of block.
TAPCON fasteners are screwed into holes drilled with tungsten tipped concrete drill bits sized for the screw sizes ( most easily with a hammer drill) . 1/4” screws are rated for 700 lb pullout in concrete and 900 lb. in shear. Keep in mind that an engineer will usually specify loads 1/4 of rated strength.
For 3/16” or 1/4” screws I’d use the TAPCON supplied bits perfectly sized to the screws. Larger sizes use standard ANSI concrete bits. The largest I’ve used are 1/2” and they are quite secure in concrete, being rated to 7,414 lbs in pullout and almost 12,000 lbs in shear ( in concrete) they are often used to secure machinery.
TAPCON bits come in blue coated, 410 stainless, and zinc plated, depending on moisture and treated lumber conditions. They come in hex head and #3 Phillips flathead ( maybe other heads).
https://www.tapcon.com/products/concrete-screw-anchors
There are competing structural fasteners ( Headlox , Simpson), but I’ve only used then in wood, not into block.
Keep in mind your limiting factor will be the condition and type of the concrete block wall. If it is crumbly, all bets are off.
You will also get a bit help if you also use construction adhesive between the shelves and the wall surface.
Edit:
The technical pdf does include structural ratings for lightweight and heavyweight concrete block, including mention of the 1/4 safety factor.
- This reply was modified 5 years, 10 months ago by Larry Geib.
- This reply was modified 5 years, 10 months ago by Larry Geib.