Plinth around base of property - should there be a gap?

[Minino1]

I recently had an extension built - a number of problems are now becoming apparent, unfortunately I wasn't around when the work was being finished. Anyway, this is probably an obvious point to those in the know but there is a plinth around the base of the extension - it has a metal strip along the top, and there is a gap behind it, perhaps 2-4mm. Rain water will presumably run down into that gap - I am wondering whether the gap should have been closed (if so with what?) or whether this is normal/correct and its to allow some sort of air circulation to allow moisture to dry out?

The same plinth is at the front of the property but the walls were rendered and the render protrudes beyond the plinth so water can't run down if that makes sense.

Many thanks

 

[yorksbuilder]

Where is your DPC?

 

[Minino1]

Hello, I'm fairly sure the DPC is one brick below the top of the plinth. Please see the photos which I think show that the DPC was level with the bottom of the door, and the plinth raises up one brick above. I guess that's bad news as the plinth could potentially be increasing moisture above the DPC?

I wasn't here at the time when most of the construction work was underway, and you cannot see any sign of the DPC even where there isn't a plinth. There haven't been any signs of damp inside the home - its 12 months since the main construction was finished. But I can now see they took so many shortcuts with the work I am starting to worry about everything I look at.

 

[Minino1]

I also don't really understand why they included airbricks when its a concrete slab foundation, not block and beam. Seems odd to me.

 

[yorksbuilder]

They've used a standard render stop bead. Hopefully its stainless steel.

There are many profiles including bellcast and drip strips. These are mainly used at the bottom of the render, not the 'top'

Why do you think rain will run behind it? Is it exposed to driving rain?
If you want it to be sealed maybe ask your builder or the rendering company to come back and seal it with an external grade silicone sealant.

 

[Minino1]

Many thanks, that's good to know. Yes it does look to be stainless steel. The plasterer was actually quite good and seems to have done a decent job, I was just concerned that rainwater might run down that gap and then cause a damp issue. I intend to paint the plinth with a breathable plinth paint. The builder has done a disappearing act but I could fill the gap myself with silicone, if its advisable, or I can just leave it if its not a big risk. I can't see any signs of damp so far.

Any thoughts on why the airbricks are there given that its a concrete slab foundation.