Concrete blocks or aerated?

[BadgerBadger]

Looking through our detailed designs and we're currently on aerated blocks throughout. What are people's thoughts around concrete blocks vs aerated types such as Celcon or Thermalite?

 

Are there issues with strength of internal wall fixings (shelves, TVs etc.) with the lightweight blocks?  Our insulation U value would drop slightly with a regular concrete block, but could there be benefits with thermal mass/delay?  We have a couple of long runs where bed reinforcement has been specified to stop expansion cracking, is this just a problem with the lightweight blocks?

 

 

[Mr Punter]

Aerated blocks are more prone to crumble and not good for fixing to or plastering.  Medium density aggregate blocks are good allrounders but you lose a bit of insulation.  It may make no difference to the bed reinforcement requirement but best to check with the SE.

[tonyshouse]

Aerated blocks crack far too easily, move around and are naff in comparison to medium density blocks. No cracks is normal with them. 

[MAB]

It is important that the mortar mix is correct and not too strong or it can cause cracks.

There is a golden rule in the building industry that states ‘mortar should never be stronger than the material it is joining’.

Some good advice here:-

https://skill-builder.uk/aircrete-blocks

 

These Fischer Duopower wall plugs work well:-

https://www.screwfix.com/p/fischer-duopower-wall-plugs-6mm-100-pack/1030P?tc=KT1&ds_kid=92700048793290424&ds_rl=1249413&gclid=EAIaIQobChMI3oXXyb6R7AIV0-ntCh10cQq9EAQYASABEgIxmPD_BwE&gclsrc=aw.ds

 

Some info in this earlier BuildHub thread below may also help:-

 

[joe90]

I just don’t like aerated blocks, medium solid for me every time, I like solid fixings into a solid wall.

[tonyshouse]

Definitely do NOT use dot and dab

[Dave Jones]

use stud instead!

[tonyshouse]

Yuk!

[WWilts]

On 25/09/2021 at 21:51, tonyshouse said:

Definitely do NOT use dot and dab

Ouch.
What are the worst things about dot and dab?

[tonyshouse]

Air leakage, thermal bypass, cold draughts, living in plasterboard tent, draughts everywhere, for starters 

[CalvinHobbes]

Is Fermacell ok?

[Mr Punter]

7 minutes ago, CalvinHobbes said:

Is Fermacell ok?

 

It is a pain to work with, very expensive, heavy, not mould resistant, the FST skim is useless, your sparky and dry liners will hate you, but otherwise it is average.

[tonyshouse]

Does not solve any of the problems I highlighted above except now you live in a fermacel tent instead of a plasterboard one