I am building a small (4m x 4m) workshop that will have air conditioning. It's being built with AAC block walls and an insulated ceiling. The construction is fairly simple - 4 main posts with a beam around the base between the posts. This beam is 40cm deep and sat on the ground. The final floor level will be about 45cm above the surrounding ground.

I plan to fill the base with dirt, then sand, then a layer of AAC blocks, before pouring concrete on top of these - to get a floor that has some level of insulation - any better ideas? I don't really want to use polystyrene because termites can eat it - I have had a cooler eaten through...  AAC blocks are pretty cheap these days. 7cm blocks laid flat on their sides will only work out to be about 130 Baht per square meter - a total for this building of a little over B2,000

 

Well I wouldnt.

only this week on the forum we have been discussing dpcs and the fact that aac blocks are potentially like tea bags.

 

filling a sub floor with loose blocks and the like without adequate compaction can lead to settlement and movement in your top slab.

 

stick to a traditional board insualtion if you can, one thats foil lined will help against critters but really termites are not interested on polystyrene, they prefer wood.

I concur that the blocks will cost about 130bt/m2 but what about there R value.

you will find they are only about R-3, so R-1 per inch

 

I was comparing and constrasting loft insulation last week and pretty much all brands/varieties are between R5 to R7 per inch, thats a big difference.

...and a 3 inch thickness roll covering 2.4m2 costs about 200bt

 

I am not saying to use loft insulation , but its horses for courses, blocks are for walls,  board insulation is was floors and ceilings, soft insulation is for lofts and cavities.

 

If you really want to do it traditionally, I would go with a big damp proof membrane laid on your level sand bed, then use a 2 or 3 inch insulation board or polystyrene and then pour the concrete onto the insualtion.

leave enough dpm at the edges to turn up and use as a dpc for your qcon blocks.

 

Dont be worried about termites, the membrane should at least give them the elbow and you are preventing that very rare thing here...rising damp.

 

 

Thank you for the advice eyecatcher. I had also been contemplating the AAC sponge issue...

Why not leave a air gap underneath? dig out then use concrete "floor planks"

Q-Con has also AAC floor plank in their product range.

Vapor barriers, yes.  But insulating a slab?  Interesting.  What are you insulating it from?

Thanks for all of the input.  Floor planks would work to leave a void, but won't really insulate the AC cooled slab from the heat beneath the house. AAC planks may be an excellent solution though. I wasn't aware there was such a thing. Thank you juehoe.  ☺️   I guess it's that or a polystyrene layer if without planks... 

Depending on how serious you are to have insulated floor you could insulate under the planks as they were laid, either by attaching polystyrene or even spraying insulating foam, would get difficult on the last piece to be laid though!

10 hours ago, juehoe said:

Q-Con has also AAC floor plank in their product range.

really!

is it 1m deep by any chance?

you need to handle that with kid gloves I reckon.

Did anyone ever use their aac lintels?

To get compressive strength they would surely need rebar at the bottom already cast in. Is that the case OR can you trim them with a saw like the blocks

 

the same will obviously apply to planks (if they exist) but in abundance , not the fabric mesh in the 50mm connie planks

Back to the topic... I'm still curious why you think the ground under a slab will get hot and need insulation?  'splain it to me Lucy.