Fixing to Thermalite blocks

[The Medway Handyman]

Anyone had any experience of fixing into rendered 'Fermalite' (as the builder called them) blocks?

I'm guessing resin is the method?

[Tim Watts]

On Tuesday 30 July 2013 21:45 The Medway Handyman wrote in uk.d-i-y:

"Thermalite" probably aka "cheeseblocks".

Yes. They are horrible. But wih the right fixing you can get it strong.

For basic fixings, Fischer S8's will do (5mm screw) or other sizes in the same range.

For a stronger fixing for heavy cabinets and shelves, try Fischer SX 8x65

(other sizes available). Serrations all down a very ling body (65mm in the above case). Probably hang a radiator on those OK. I can get screws nice and tight with the SX fixings.

If hanging something with high potential pullout forces or where collapse is a disaster (basin without pedastal, toilet cistern) I used stainless stud resin'ed in to 3/4 the thickness of the wall. If that pulls out it will have to take a large lump of block with it. Sounds complicated, but no real hassle.

If you are stuck, take any decent plug and apply some araldite to the outside before inserting into the hole.

The biggest problem with Thermalite blocks in if the plug twists, it can grind out the hole and lose traction.

[Tim Watts]

On Tuesday 30 July 2013 22:00 Tim Watts wrote in uk.d-i-y:

OK - I just saw the subject. Still "aka cheeseblocks".

[Stephen H]

I have successfully hung a 38kW condensing combi boiler on these thermalite blocks...

basically I drill through completely through the thermalite block using a slow speed straight drill and no hammer into the cavity.

if you don't drill through, you will find that you won't be able to push the the plug in or screw fully home as there will be a build up of thermalite dust at the end of the drilled hole. The drilling through of a through hole allows this dust to escape into the cavity.

I then use window frame fixers that are the same depth as the hole just drilled.

This works if you are screwing radiator brackets made of thin sheet metal.

If you're fixing wood battens, I find I have to buy the next length up of frame fixers, take the screws out of that and use these longer screws instead of the ones supplied with the frame fixers you are actually using.

I then end up with a load of short screws and too long wall plus so these end up going in the bin.

The araldite is a good tip, so is no-more nails. Sometimes I use no-more nails to glue the wall plug in the day before and then do the screwing the following day.

[Dave Liquorice]

There are a myriad of different blocks out there. has the builder ID'd them correctly. Are they solid blocks or the ones with two square holes up the middle with a wall thickness not much over and inch?

After that all I can say is "good luck".

[polygonum]

In similar situations (soft blocks but not actually Thermalite) I have used polyurethane glue - which has the advantage of modest foaming.

[Cash]

Simply partially withdrawing and reinserting the drill bit a few times (whilst the drill is still turning) during the drilling process will clear the dust and resolve that problem - exactly the same method that you would use when drilling wood, metal, concrete, stone etc to any (relatively) great depth. Works every time for me.

Cash

[spuorgelgoog]

If it's an awning I'd consider going right through the wall and to a steel load spreader plate inside :-)

Owain

[harryagain]

You can get special "rawlplugs" for the job but they are expensive.

For most jobs, drill a deep hole (say an inch "too deep") and push a normal plug down to the bottom and use long screws slightly oversized for that plug.

[Tim Watts]

On Wednesday 31 July 2013 07:03 harryagain wrote in uk.d-i-y:

You really are Drivel reincarnate aren't you...

[The Natural Philosopher]

Nah. the stuff is just strong enough to need no more than a normal plastic plug, and just weak enough that drilling an accurate hole with a masonry drill is simple, No hammer action needed.

I've done kitchens in rooms made of that stuff, and its one of the easiest materials to fix things to.

[The Natural Philosopher]

I used to use the motor fan on the drill to blow the dust out

[sm_jamieson]

As others have said, long frame fixings are OK. I always drill the hole 0.5mm smaller than the specified size (usually 7.5mm) with a normal drill bit (not masonry), which ensures a nice tight fit. Simon.

[srp]

.5mm smaller than the specified size (usually 7.5mm) with a normal drill bi t (not masonry), which ensures a nice tight fit.

my house has something like thermalite blocks, my kitchen cabinets are held up with normal 8mm wall bolts. I have shelves held up with normal screws a nd wall plugs. The blocks are so soft that you can drill into them with har dly any pressure on the drill at all.

I find that you just need to be careful to get the right sized drill/ plug / screw combination and it it's normally OK. Having said that the internal divider walls are something different again, I mounted my Plasma upstairs b y putting bolts all the way through the wall,at least it ain't going any w ere !

Simon

[andrew]

We use these:

They hold well as you screw into them because of the squarish end, and the manufacturers claim higher strength than resin. Screwfix used to stock them, but I can't see them now. As others have said, you need to drill without any hammer action. It actually works best with a non-masonry bit - the block manufacturers say to use wood tools for working with the blocks.

A

[RobertL]

Although nobody seems to like resin (and studs), that is exactly what I have just been using and it went very smoothly. It was much easier than using expanding fixings.

I've been hanging kitchen wall units on a wall that is part old brick and part thermalite block covered. The old brickwork has lime plaster on it.

I used resin studs (6mm diam, 110mm long) so the load is not taken on the plaster and also because the blocks seem to crumble up if squeezed so I thought expanding fixings would not hold.

One trick I evolved was to use a dob of plasticine to hold each stud in exactly the right position while the resin cured. They had to project just 9mm so they held the fixings (with nuts) but did not foul the back of the wall units.

[Tim Watts]

On Thursday 01 August 2013 12:44 RobertL wrote in uk.d-i-y:

Good idea with the plastercine.

I have used a plank of wood screwed to the wall and with holes drilled through to locate the studs. That was for a toilet cistern where the studs were a very close fit (zero room for error) and the holes in the ceramic where not even quite straight. I held the wood to the cistern and ran a drill through both. Then using the studs to locate the wood, drew an outline of the cistern top and top sides.

Then used those lines as a reference to hang the wood straight and level on the wall.