Fasteners In A Block Wall

[Anonymous-0]

I'd like to mount a mirror to my cement block basement wall. It seems people usually drill into the mortar rather than the block. What is the reason for this? Would drilling into the block compromise its strength and possibly lead to cracking?


Thank you,
Glenn F.

 

[Anonymous-0]

My experience has been that expansion anchors will crack cement blocks. I have drilled in to the hollow area and used toggle bolts with success.

 

[Jim B. in OH]

TAP-CON works well, just make sure you use the right size bit or they won't work and you will cuss them, atleast thats what I did. I don't use anything else now. Jim

 

[dave guest]

Mounting electrical panels we would use A&J. A lead anchor that expands with tool and has internal thread, commonly 1/4 - 20. Only ones would fall out was in mortar. If you never used them before, there is an easier one that looks like a big rivet. You drill hole. Push it in and hit the center that looks like a nail. Very easy and very strong. Toggle bolts are great and strong, just a little tricky sometimes and holes need to be located in the hollows of the block.

 

[tractormarkb]

Ive had god luck just using drywall screws in the cinder block. Just drill them in with no anchor they hold good.

 

[Anonymous-0]

I think many people find that the mortar is softer and that they won't penetrate through it, vs drilling in the center of a hollow concrete masonry unit(CMU)and penetrating a hollow cell. In some designs of large buildings, the CMU can be high strength, I have used certified 5000 psi CMU with 3000 PSI mortar, fully grouted for structural walls, the mortar was definitely softer than the high strength CMU, you can easily differentiate between the 2 when drilling to install a fastener or using a powder actuated fastner

There are a variety of fasteners to consider for masonry applications, if it is a small mirror, a threaded type, with or without an insert or sleeve would work fine, tapcon or similar. There are now a threaded type of concrete bolt, kind of a giant tapcon, but these still don't have the higher strength properties like an expansion type fastener and or other types. If you look through a Hilti catalog, technical information is provided for all fastener types and they do list shear, tension and other strength properties. Just reading the catalog can be a learning experience for anyone new to masonry fasteners.

If the CMU are hollow, probably standard strength, a threaded type of fastener, one with an insert or sleeve would be fine, as would one with a toggle, as long as this is not a giant mirror with substantial weight that would be dangerous if it fell. The CMU should not crack or weaken. Do not over tighten the fastener, snug it up tight but don't crank on it until it fails. The CMU has cells and if they are hollow, the depth of the fasteners thread engagement is going to be the same as the wall thickness of the cell. If you were to use an expansion type fastener, like a 1/4" Hilti expansion bolt, you would drill a hole and have to set the expanding part of the fastner within the thickness of the wall of the CMU cell, or gain some depth by using the mortar joint, these won't work if you penetrate through and try to tighten them up but I hve used them on hollow CMU, just have to find the sweet spot and get them to lock in the cell wall. It is possible to pull one of these types through and spall the area around the hole, but I doubt it would crack, unless the CMU is in a deteriorated state, it would just make a hole. There are also epoxy type fastners, drill hole, inject epoxy or insert tubes that will be crushed and activated by the fastener when you place it in the hole.

Many times in large buildings, certain areas of CMU walls will be filled with mortar or grout, coordinating with other building components that will need suitable places to fasten.

 

[Anonymous-0]

Thank you to each of you who responded. I always learn a lot from you guys.

Glenn F.

 

[Anonymous-0]

In electrical work you use whats called a hollow wall set.The anchor screws onto the setting tool and as you pound with a hammer expands forcfully into the block.If no one has a hollow wall set then its 3/8 toggles.The mortar area is ideal for smaller blue [plastic] anchors if it hangs your object at the correct height.In your case I would use mortar seams and plastic anchors.They hold things like that ok.Hilti also makes every type anchor and epoxy product for concrete fastening.If you use toggles you must break into the hollow of the block.It helps to have some block around you can study where the hollows are.Modern block is concrete not cinder and is farly tough.I would not worry about cracking block.

 

[jose bagge]

When hanging ahrd lines for our compressors in the shops we drill into the block all the time, and secure our pipe clamps with toggle bolts just like you would with drywall. We run 40-50' of 2" with many individual 1" drops, so it's quite heavy- and probably use a single toggle every 8-10', It will support a lot of weight

 

[Sparktrician]

Depends on how heavy the item is. For a mirror, i would use tapcons (blue threaded screws) they work well in cinder block and concrete for light objects. For heavier, the lead head anchors are good. I TRY to get my anchors in the block, and avoid the mortar. STAY AWAY FROM PLASTIC ANCHORS!! they will pull out. Toggle bolts are ok, but i rarely use them. If in drywall, use a "ZIP IT". you will pull a chunk of sheetrock off before those pull out....GOOD LUCK!!!

 

[El Toro]

I would use the the epoxy as Billy suggested. Hal