Drilling into masonry to mount shelf

Hi all,

I've lurked here on-and-off for the past half year, learning about DIY jobs around the house, but I have a pretty specific situation I need some advice on for my latest project.

I want to mount a wall shelf, onto a masonry wall. I actually don't know whether it's a concrete or brick wall, which sounds pretty dumb - how do I tell?

I've borrowed a hammer drill, and I also have a 5.5mm masonry drill bit for the job. The drill bit says to use with red plugs, so I also went and bought red Ramset Starplugs, as well as 8gauge screws.

However, I've realised that the screw heads are only a tiny bit bigger than the mounting holes on the bracket. Even though it's impossible for the screws to fall through the holes, it feels a bit iffy, and I think ideally I should get larger screws. I've considered using washers to hold them more securely against the bracket, but I doubt this is a good practice.

So I guess I have a few questions:
- Can I just get 10gauge screws to use with the red plugs? I've seen charts that say red plugs can accept up to 10g screws, but the Ramset ones I bought, actually have markings on them that say size "8-9". Is it a bad idea to force 10gauge screws into them?

- The other alternative would be to get larger plugs to fit the 10gauge screws. However, I didn't see any brown plugs at Bunnings when I went, are brown plugs commonly sold in hardware stores? If I take this option, I would also have to buy a new bigger masonry drill bit.

This job has been dragging on for ages, so I am keen to get it done. Any comments/suggestions from you guys would be greatly appreciated!

Thanks,
Andrew

a. Use a screw with a bigger head,
b. Use a washer under the head of the screw,
c. Use a larger size screw.

Dear Andrew,

I reckon you're dealing with cement-rendered brick, because straight concrete walls are fairly rare in house construction.

I would therefore opt for using the bigger screws in Green plugs, because the bigger screws will give you more reach into the bricks for better strength. It says on the Ramset packet to use a 6.5mm Masonry Bit with the 7mm Green plugs, and I agree - always use a smaller bit than the diameter of the plug. You could go for either a 6.5mm bit with 10g screws, or a 7mm bit with 12g screws if you have trouble finding the 6.5mm bit. A 1/4" bit (which is about 6.4mm) would also work with the 10g screws.

Make sure you don't overdrill the depth by too much, and don't drill any faster than top speed in 1st gear, or about half of maximum speed if the drill doesn't have 2 gears. And make sure you blow out the holes with a straw (and your eyes closed :wink:) before you put the plugs into them.

Good Luck,
Batpig.

Do what Batpig said except don't close your eyes use your safety glasses :)

Wow, thanks for the informative replies guys.

I've just gone and bought:
- green plugs, 50mm long
- 10-gauge screws, 50mm long as well, and
- a new 6.5mm drill bit

With the steel bracket itself being about 2mm think, the screw should be embedded into the wall about 48mm deep, which means the plug will be 2mm deeper in the hole I will drill. I assume this is not a problem?

Also, are washers still recommended? In my haste, I forgot to buy washers, so if they are advisable, I will have to make another trip!

By the way, cement-rendered brick sounds like a likely scenario... I live in an apartment complex, if that makes a difference.