Soil-stack unfinished?

We've always noticed a bad smell in our bathroom, even though any building work finished almost 8 years ago.

I have just climbed along a little loft section of our extension, and around a corner to find that the soil-stack finishes inside the loft - just an open end of grey soil pipe -about 18" above the highest inlet (from the upstairs loo) - surely it should have gone out through the roof, with a cap on it?

Is this breaking regulations, laws, etc - or just shoddy workmanship?

Now that we are putting the house on the market - is there any easy fix, other than extending it up through the roof of the extension?

depends on how you foul system is vented - do you have any other stacks/vent pipe on your property?
The stack should not be left in it's current state - the most obvious fix is an AAV (durgo) - this will at least stop sewer gases venting into your roofspace

Thanks for your reply, newboy. I have no other stacks, vents, etc in my property - excuse my ignorance, but an AAV Durgo means nothing to me......

an air admitance valve....alows air into the pipe but not smelly air out...from screwfix or similar

Thanks, guys.

OJ