Feb 26, 2017
Sometimes clients ask for it. Sometimes builders promote it as a selling point.
If you're aiming for the highest quality, I'm against single-pour foundations.
A book called How to Make Crack-Free Concrete (by Fumio Iwase) has been published by Nikkei Architecture. According to it, free water inside the concrete invites cracking, and consolidation (vibration) is important to remove it. Re-vibration (re-consolidation) is said to be best performed at least 30 minutes after the pour.
When using floating forms, you pour the slab concrete first, wait until it has firmed up to a degree, then continue pouring the stem walls.
With that method, thorough consolidation becomes difficult. If you vibrate carefully, the concrete blows up from beneath the formwork and pouring becomes hard.
I think it's better to properly handle the laitance and do a two-stage pour. If you opt for single-pour for the sake of waterproofing and termite-proofing, but the consolidation is poor and honeycombs form, you've defeated the purpose.
