Creating a firm anchor in "no-fines" wall for hanging boiler

[DIYalot]

Hi. My boiler was hung on a metal fixing plate (44 Cm x 6 Cm) that was screwed onto a "no-fines" concrete wall. It's now off the wall, but it needs putting back up again. But, I'm not happy trying to screw it back onto the "no fines" wall. I don't think it's very safe to do so.

What I want to do is prepare the wall, so that when it comes to drilling the wall, the drill will go straight, and the rawlplugs will fit nice and snug.

I will need to chisel out the "no-fines" wall, and make a cavity, an area somewhat larger than the fixing plate. Then fill with cement I guess. I was thinking about making the cavity about 75mm deep.

Is there anything I should know about this project? Of course, I don't want the cement, by and by, to come away from the cavity. Thanks.

 

[Dan Robinson]

What does the installer say?

 

[JohnD]

no, use a resin injection kit instead.

 

[DIYalot]

I'm glad I asked. So, I need a chemical mortar or resin to fill the cavity with. And that is the proper way to do this. Thanks. By the way, I'm not installing the boiler, just seeking to prepare the wall correctly for an installer.

 

[JohnD]

No cavity.

Have a look at the instructions. Fischer are good.

 

[muggles]

By the way, I'm not installing the boiler, just seeking to prepare the wall correctly for an installer.

Think on this - if you prepare the wall, and the boiler falls off the wall, the installer will most likely blame your wall preparation. If you leave the preparation to the installer, the risk is entirely on his head

 

[simond]

http://www.concrete.org.uk/fingertips-nuggets.asp?cmd=display&id=903

 

[gas112]

be a lot less hassle just using an sds drill instead of a standard hammer drill and drilling the proper size holes but bit deeper and use 3 1/2 or at worse 4 inch screws .I have hung thousands of boilers , big rads and heaters onto Nofines and never had to do what your contmplating

 

[Agile]

The problem is that it is difficult to guess exactly what the characteristics of your particular wall are going to be.

I would aim to use long Fischer type bolts and drill a few test holes using an SDS standard masonry drill and see how that goes.

But the aggregate is flint ( Mohs 7 ) and that is nearly as hard as diamond ( Mohs 10 ). So the only drill which will be expected to make a clean hole will be a diamond drill.

But as said, its the installer's responsibility to ensure the bracket is adequately fixed onto the wall.

If I have any doubts then I use a multiplicity of fixings so the load per bolt is much reduced.

Tony

 

[mogget]

What are you talking about Tony, tungsten carbide is mohs 9.

 

[Agile]

Quite so but try drilling a hole in a flint stone with a TC tipped masonry drill.

Masonry drills are designed to hammer a hole and would just bounce off.

I expect my HSS TC drills would though!

Tony

 

[JohnD]

the Mohs scale is relative, but not proportional

 

[mogget]

I am familiar with the problem of an sds drill deflecting off hard aggregate. Granted the tc bit will wear more quickly, but is cheaper, and the op is talking about a single job.

Op, if you wish to add a mortar/concrete fillet, the way to stop it pulling out is to undercut the sides of the cavity you are proposing.

 

[Agile]

Just like a dentist does with an amalgam filling.

But to be safe needs to be good depth in the wall. Not just 50 mm !

Tony

 

[mogget]

Indeed agree that 50mm is inadequate.