Lightweight concrete screw - no need for plugs?

[Jacon]

Hi When I read about light concrete screws, it seems like they can be screwed directly into light concrete for fastening without plugs? Is it really that brilliant or have I misunderstood? Do you need to pre-drill anything in the concrete?

Yesterday, I discovered that the frame of our front door has come loose at the top, so the whole package is falling out a few cm. When I look in the gap, it seems like it was previously screwed with plugs and that the concrete has broken a little at the plug, creating space for the plug and screw to move. I was thinking of solving it simply by just screwing in a few new screws in new spots in the frame, but if I have to use plugs, they will create large holes as the plugs must go through the frame.

 

[smurfen72]

You first drill and then insert the screw; it sits well, but I don't think you can keep pulling it in and out multiple times.

 

[vanpire]

You shouldn't pre-drill for lightweight concrete screws!

 

[Jacon]

Went to XL to buy screws, but he absolutely recommended nail plugs in blåbetong instead because it was so porous. So I bought those and inserted the plugs through the frame and into the concrete. He recommended that you could glue the plugs beforehand to make the concrete hold together even more.

 

[vanpire]

Sounds like a reasonable solution

 

[smurfen72]

You should not pre-drill for lightweight concrete screws!

The lightweight concrete screws I've used have required pre-drilling, but they have admittedly been quite large, 10-12 mm.

 

[Jacon]

Secured the frame with nail plugs now and it seems to have settled well. But I wasn't prepared for the last cm to be so darn hard to nail in. But maybe it's the final expansion of the plug that does it.

Is it possible to unscrew the nails even if they have been hammered in? Thinking about the day I need to replace the entire door including the frame.

 

[smurfen72]

They are supposed to be screwed out, but it rarely works; however, they can be sawed off. If the door is poorly fitted, you can add some expanding foam, and it will stay in place, but it can't be adjusted afterward.

 

[tommib]

Fastening in lightweight concrete, I use Fischer GB. They hold like a rock, even for the Elfa shelves in the storage that carry various heavy items.

 

[Jacon]

Ok. According to the description, these are for lighter shelves, mirrors, pictures, etc. Moreover, it would have required me to remove the frame first as I understand the construction.

 

[tommib]

Yes. The Fischer plugs are driven in with a hammer or mallet and rotate a quarter turn on the way in.
Now I see in the datasheet that it mentions various lighter items, but I have mounted things like shelving units with them without any issues. Admittedly, the load is primarily longitudinally along the wall, so that might be why they hold so well.....

 

[smurfen72]

But you're drilling first, right?

 

[hnurre]

Like this?

Or do you mean that there are ones so small that you don’t need to pre-drill?

 

[tommib]

Yes, you first drill (with wood drill, gives the nicest hole)

 

[ensamresande]

Fastened the frame with nail plugs now and it seems to have set well. But I wasn't prepared for the last cm to be so damn hard to nail in. But maybe it's the final expansion of the plug that does it.

Can the nails be unscrewed even if they've been driven in? Thinking about the day I need to replace the entire door, including the frame.

But if it was so hard to nail in the last bit, you might have drilled too short a hole (it should be a few centimeters longer than the plug) and/or not cleaned the hole properly before you drove in the plug (compressed air in a can is handy).

The important thing with "heavy" fastening in lightweight concrete is that it's long so it goes far into the wall. Nail plugs tend to be quite long, so they usually sit accordingly. Facade plugs are even better.