Are my Builders Using the Appropriate Bricks for my Extension? Drainage pipes, concrete, footings and foundations. Post your questions and find answers here

[Newbie123]

I'm having my kitchen extended, but am a little confused so am hoping someone can help me.
The builders have laid some bricks around the perimeter down below the damp course, but these are regular bricks. I thought that they would have used engineering "blue" bricks all the way around as wouldn't normal bricks just soak up the rain and frost?
They have delivered blue bricks for future use, but I was wondering if what they have done so far is "right" and if not, then I can at least approach them and state my case.

Thanks

[welsh brickie]

If the bricks are being rendered over then its ok to use common brick.

[welsh brickie]

If the bricks are being rendered over then its ok to use common engineering bricks.