Concrete screws into breeze block

[Michael Chare]

Do concrete screws grip properly when inserted into breeze block, or will I have to use a rawlplug?

[mal]

Pretty good actually.

If you follow the instructions you will see no mention of a rawlplug. they have their drawbacks but ill never go back to plugs and screws if i can use concrete screws they are very firm and hold huge loads but you must follow the instructions.

Malc

[Michael Chare]

Thank you. I have not seen as many instructions as I would like. I think that for a 7.5mm screw you have to drill a 6mm hole. One video I found said the screw had to go about 1.5" into the hole, another said 50mm.

[mal]

Its simply what size drill and they go to great lengths to tell you to blow the hole free of dust. Mine also said that you should use an impact driver but when i did the torkx bits kept snapping. I used screws the full depth of the breezeblock i didnt see the point in going less because i needed them for a load with a lot of weight and leverage.

Malc

[TMH]

Agreed. Use them all the time.

[Bill Wright]

Is it a breeze block or something softer like Thermalite?

Bill

[Brian Gaff]

From my experience nothing grips very well in that stuff, but like many things there is Breeze block and breeze block. some is quite dense, while other stuff seems internally to be, indeed mostly breeze! IE lots of holes.

Brian

[Robin]

[Tricky Dicky]

My understanding is that the term "Breeze block" refers to the type made mainly of cinders, whereas a concrete block is well, a concrete block. I think I would be wary of using concrete bolts/screws in the cinder blocks owing to the point Brian made about gaps in the block and they tend to be more friable. A Thermalite although soft enough to almost make a hole with your finger may well take a concrete screw, if I remember correctly one manufacturer (Plas Plugs I think) made plastic wall plugs with a coarse thread that you screwed into the block before pushing in a locking pin. As concrete screws have a coarse thread they may well hold though I do not think you will be able to do much adjustment before the hole loses any threading.

Richard

[The Natural Philosopher]

What then do you calls thermalite as?

In my mind there are at least three types - concrete, breeze, and foamed lightweight block.

[PeterC]

My first encounter with Thermalite was in the '70s. Hole, plug, screw, crack running both up and down, through the mortar and the adjacent blocks. Hated the stuff ever since.

[Tricky Dicky]

My first encounter with them was also in the seventies the guy we bought our first house from and a neighbour used some lightweight concrete blocks bizzarly a mixture of wood chips and concrete to build garden walls then wondered why the blocks disintegrated, the neighbour told me they were Thermalite.

The second house had a garage and kitchen extension built and the internal walls were the traditional grey Thermalite stamped version (spit). The only anchors that worked effectively and crucially allowed you undo the screw without loosening the fixing were made by Fischer. They were a nylon plug with four helical vanes down the side in a slow spiral that had to be hammered into a pilot hole, could sometimes be a problem near a mortar line but generally an excellent fixing. I note they are no longer made but instead Fisher recommend their universal plugs for aerated concrete, don't know how effective they are not having any Thermalite in our current house.

I also experienced your cracking problem when two Mr. Men installed a roller door at the previous garage, I told them not use hammer action on their drills, no they knew better, twice as many holes later they finally managed to get some sound fixings in place.

Richard

[newshound]

There is breeze block, made from some sort of industrial clinker, but not since about the 1950's. Then there are concrete blocks which come in various densities although I think "medium density" is the one found most often in domestic situations. IIRC high density is recommended below ground level. Then there are the lightweight blocks like thermalite. Easily recognised by their weight and the fact that they can almost be scratched with a thumbnail.

Breeze block could be quite difficult to drill.

Concrete screws should be fine in medium density concrete. They won't have much strength in thermalite.

[Tim Watts]

I hate it too.

Even good plugs seem to need araldite to stop them spinning.

I have to hang a cistern on one such wall soon. nLast time I did this, it was resin 6mm (IIRC) stainless stud 3.5" deep into the wall.

That requires perfect alighnment which I did with a bit of 2x4" wood as a jig.

Not looking forward to doing it again. Wondering this time if to make up a metal plate intermediate bracket...

[tabbypurr]

Lightweight blocks now are AAC.

NT

[newshound]

AAC?

They get their properties from the glass spheres formed from Pulverised Fuel Ash from coal fired power stations. Presumably they are still mining the lagoons at closed UK plant, but will we end up importing it?

[tabbypurr]

Autoclaved aerated concrete

[Jon Fairbairn]

Not only you. The upstairs internal partitions in our house are made of the stuff. Horrible dirty stuff, and unexpectedly thin as I discovered to my embarrassment when sinking a deep backbox for a shaver socket.

[Andy Burns]

My house has 60's breeze blocks (that take quite a bit of chiselling when you need to chase into them, unlike the modern lightweight blocks you can scratch with a fingernail).

When altering a stud partition wall, I used some 6" concrete screws at the stud/block junction ... no problems, the bottom plate of the wall was also screwed down into the concrete floor with the same screws; but the top plate was screwed up into the first floor joists, so not entirely dependant on the concrete screws into blocks.

[sm_jamieson]

Hanging radiators on thermalite blocks, I replaced some plasterboard with plywood (fixed with quite a few screw/plugs) and screwed the radiator brackets onto that.

Other trick if the bracket has more that one screw is to put then screws in at diverging angles. That way the pullout force is at an angle to the screws - you have a sort of "wedge" action.

On my extension I used the slightly denser 7N AAC blocks as the "normal" ones seemed SO flimsy.

Simon.