aircrete fixings - that works !

[sm_jamieson]

Been doing some experiments fixing to an aircrete block - just for something to do before I remembered I have to finish making the new garden gate ! Anyway, I was perplexed about fixing to aircrete previously. Well, I screwed an 80mm x 5mm spax screw directly into the block, and tried to pull it out with a mole grip. No chance ! So I think thats the answer. Just screw a long screw straight in, no pilot hole or anything. Job done. I guess a fairly course single-thread screw would be best to use, and screw downwards at a slight angle just to be sure. Simon.

[dom]

More expensive, but multimonti are ideal for this sort of job:

've tried levering them out of masonry with a crowbar to no effect.

[The Medway Handyman]

> I've tried levering them out of masonry with a crowbar to no effect. Agreed. Multi Montis are the mutts nuts. Incredibly strong fixing.

[TheOldFellow]

>

I used them for the battens behind drywall onto concrete bricks. Fantastic solution. Immovable, yet easy to drill and screw. You need a good high-torque drill-driver though.

R.

[Mark Dumbrill]

>>> I've tried levering them out of masonry with a crowbar to no effect. >

I need to fix a length of cabinet hanging rail in my kitchen to 4" thermalite blocks for new wall cabinets, see here for an example:

was going to use resin fixings with 6mm threaded studs, but it sounds as if these concrete screws would be ideal, eg.

?_dyncharset=UTF-8&fh_search=44159From reading this thread this sounds OK. Can anyone confirm?

[TheOldFellow]

?_dyncharset=UTF-8&fh_search=44159>

I've used them for that (although I used the torq-headed countersunk ones. It's only two years since, but no problems - and my cabinets are solid ply and bl...dy heavy.

R.

[The Medway Handyman]

>>>>> I've tried levering them out of masonry with a crowbar to no effect. >>

> I was going to use resin fixings with 6mm threaded studs, but it

?_dyncharset=UTF-8&fh_search=44159>> From reading this thread this sounds OK. Can anyone confirm?

I use the 7.5 mm ones (albeit longer ones) for bolting 6 x 2 joists to walls when building decks!

The 6mm x 60 would be more than strong enough - easier to pull a sailor off your sister than pull one out.

[sm_jamieson]

I know we have started talking about multi-monti screws here, but I'm not sure these are so good for thermalite blocks - they are intended for hard masonry or concrete where a pilot hole is drilled.

For thermalite, in light of my experiments, I think resin studs would be overkill. As I said, a long screw straight into the thermalite block, tapped lightly to get it started, would appear to be fine. Definitely don't use plastic plugs. Also you can use helical fixings that are hammered in light nails I believe. Simon.

[Mark Dumbrill]

This afternoon I tried screwing a 6 x 100mm SPAX screw into a thermalite block (Celcon) both with and without a pilot hole. Both times I could very easily pull out the scew with a crow bar which doesn't give me much confidence at all.

I don't know if I'm missing something, but I am going back to thinking I should stick with chemical fixings.

When I look at the Fischer website they have several aircrete options, but only the chemical resin is recommended for heavy items.

[TheOldFellow]

If you think about it the forces are mostly parallel to the wall, that is across the fixing - a shear force. There is only a small force attempting to pull the fixing out.

But having said that, your own confidence is worth a lot, so go with the resin. Aircrete is tricky stuff.

R.

[Mark Dumbrill]

I see your point. The trouble is that aircrete is so soft that it's difficult to get much confidence at all!

[sm_jamieson]

Oh thanks, I was just starting to get confidence in aircrete fixings and you've blown it for me again ! But are you sure with a resin fixture you could still not pull it out with a crowbar ? At some point the limit will be the local strength of the block itself ! I guess a very large blob of resin might do the job. Someone needs to experiment with the resin fixings. NOTE: there are different aircrete densities - the solar 2.8N blocks are very flimsy. I've been using the 4.0N thermalite shield - these may be a little denser and give firmer fixing. Simon.

[Mark Dumbrill]

Oh thanks, I was just starting to get confidence in aircrete fixings and you've blown it for me again ! But are you sure with a resin fixture you could still not pull it out with a crowbar ? At some point the limit will be the local strength of the block itself ! I guess a very large blob of resin might do the job. Someone needs to experiment with the resin fixings. NOTE: there are different aircrete densities - the solar 2.8N blocks are very flimsy. I've been using the 4.0N thermalite shield - these may be a little denser and give firmer fixing. Simon.

I'm not sure what type of block I'm testing on, it could well be the Solar type. I may try with some resin later this week and see what the effects are.

I've been trying a straight pull out which is obviously the worst case and perhaps unrealistic. When the fixing fails it is because a 'cylinder of material', the diameter of the screw pulls out. On this basis it is easy to see why a lot of aircrete fixings have big diameters and very coarse 'threads' to fix them in.

The advantage of resin is that it will bond uniformly to the complete inner diameter of the bore hole.

[clangers_snout]

Is there a table anywhere which details the pilot hole size required for the different sizes of Multi monti?

[Old Git]

Watch for wrap

halfway down the page you can download a pdf of the instructions which contains most of what you require to know

[clangers_snout]

> About halfway down the page you can download a pdf of the instructions

Thanks.