External walls hollow from inside

Can somebody explain what type of walls these might be? They’re not solid from the inside, or least there’s a gap between the concrete/bricks on the outside and the wall (plasterboard) on the inside.

Any insight much appreciated.

There are a fair few different types of external wall that it could be
1)brick veneer timber frame
2)dry-lined cavity or solid block
3)block walls with dabbed insulated plasterboard.

Just guessing here, but most likely to be #1 if it’s an estate build semi (1990-on), #2 if it’s a detached bungalow, #3 if it’s a 1970s/1980’s house that’s been renovated.

If I read your post correctly, Cavity walls tend to be the norm.

Most builds in the last few decades consist of a layer of external brick facing the outside, and another layer of brick on the inside. The gap allows moisture to condense and drop harmlessly down, and this is generally insulated in modern builds, and can be pumped with beads on old builds.

My parents house has two foot thick stone walls. These have plasterboard on them to make them look level and straight. Perhaps that’s what you are seeing?

The house was built early 90s and is completely detached if that helps?

Easiest way, but awkward, is to climb into attic. Check where roof slopes and meets top of external wall.

If it’s two courses of block work with cavity you will feel the cavity when you reach your hand between felt and wall. If so hopefully there is some insulation !

If you only find outer course of blocks/bricks and then a space and timber then it’s likely a timber frame.

Option 3 is to drill a hole internally and shine torch through. Then buy suitably large painting to cover!!

Thanks but this may be difficult as it’s not my house!

Where’s your sense of adventure?

Option 3 is the only way so but drill from the outside… :nin

If there is an air-vent you can sometimes take off the grill and look through into the wall.