Anybody knows what standing water means in the context of building construction?

It means water that is sitting in one place (eg. a puddle, a swamp, etc) - as opposed to 'running' water.

If it's in reference to building a house, they may be talking about providing adequate drainage so that you avoid puddles building up on the roof or around the foundations of the house. This could cause a house to rot.

Standing water is an old space alien trick to lure people into complacency so the evil aliens can implant chips in their brains. Don't go near the standing water - it has been contaminated. No doubt half the crew of the construction company have disappeared, trying to get rid of this standing water. God immediately to your hardware store and order two cases of dynamite. Set the dynamite in the middle of the standing water without looking directly at the water. Put your blasting caps in and your wire lead. walk twenty feet away and attach the detonator. Scream as loud as you can, "Die you evil aliens and push the plunger down." Next week the new owner can install a swimming pool. Hope this helped.