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Leaving Cert Construction Studies: Ground floors & radon

How often Ground floors & radon comes up on the Construction Studies papers, every year it was asked, and questions to try.

HL Asked on 4 of the last 9 Higher Level papers, most recently in 2025.

OL Asked on 4 of the last 9 Ordinary Level papers, most recently in 2023.

June 2028 is the first exam on the new Construction Studies course. These come from the 2016–2025 papers, so read them as a guide.

Ground floors & radon, Higher Level(7 marks)

Quick ones on Ground floors & radon.

(a)Why is sand blinding laid over the hardcore?
  1. To insulate the floor
  2. To stop the hardcore puncturing the membrane
  3. To level the finished floor for tiles
(b)In a solid ground floor, the rigid insulation is laid directly on?
  1. The floor finish
  2. The hardcore
  3. The radon barrier / DPM
(c)What is radon?
  1. A radioactive gas from uranium in rocks and soil
  2. A fungus in damp soil that causes timber decay in floors
  3. A gas given off when heating oil is burned
Show the answers

(a) To stop the hardcore puncturing the membrane

(b) The radon barrier / DPM

(c) A radioactive gas from uranium in rocks and soil

Your turn: Higher Level questions on Ground floors & radon.

Higher Level

Asked on 4 of the last 9 Higher Level papers, most recently in 2025.

Every paper, year by year

YearWhere it came up
2025Q1
2024Not asked
2023Q7
2022Not asked
2021Q1
2019Not asked
2018Not asked
2017Q1
2016Not asked

Links open the State Examinations Commission’s paper for that year.

More Ground floors & radon questions

Ground floors & radon, 2 marks

Why are joints in a radon barrier lapped and taped?

  1. To let ground water drain out
  2. So the slab can slide on it
  3. Gas passes through any gap
Show the answer

Gas passes through any gap

Radon moves with soil air drawn in by slight suction from the house. One untaped lap can let gas in, so the barrier must be continuous across the floor and wall.

Ground floors & radon, 3 marks

A service pipe passes through the radon barrier. How is it sealed?

  1. Fill round it with sand
  2. A top-hat collar taped to the barrier
  3. Leave a gap for the pipe to move
Show the answer

A top-hat collar taped to the barrier

Pre-formed top-hat seals fit tightly round the pipe and are taped to the membrane, keeping the gas-proof layer unbroken at every penetration.

Ground floors & radon, 2 marks

How is the radon level in an existing home measured?

  1. Detectors left in place for three months
  2. A smoke pencil test around the floor edges
  3. A blower-door test of the whole house
Show the answer

Detectors left in place for three months

Small passive detectors are placed in a bedroom and a living room for three months, then sent to a lab. Radon varies with weather and season, so short tests can mislead.

Ordinary Level

Asked on 4 of the last 9 Ordinary Level papers, most recently in 2023.

Every paper, year by year

YearWhere it came up
2025Not asked
2024Not asked
2023Q8i
2022Not asked
2021Q2
2019Not asked
2018Q1
2017Not asked
2016Q1

Links open the State Examinations Commission’s paper for that year.

More Ground floors & radon questions

Ground floors & radon, 2 marks

What is hardcore in a solid ground floor?

  1. The concrete floor slab laid on top
  2. The final tiled floor finish laid on the screed
  3. Compacted broken stone under the floor slab
Show the answer

Compacted broken stone under the floor slab

Hardcore is laid in layers and rolled to give a firm, level base that will not settle. It also lifts the floor above the ground outside.

Ground floors & radon, 3 marks

Why is a layer of sand blinding laid over the hardcore?

  1. To help radon escape up out of the ground
  2. To stop sharp stones puncturing the membrane
  3. To make the finished floor feel warmer underfoot
Show the answer

To stop sharp stones puncturing the membrane

The radon barrier or DPM is thin plastic. A smooth bed of sand covers the sharp hardcore so the membrane is not torn when it is laid and walked on.

Ground floors & radon, 3 marks

What is the purpose of a radon sump under a floor?

  1. To let radon be drawn out from under the floor
  2. To collect rainwater from under the floor
  3. To drain the septic tank into the ground
Show the answer

To let radon be drawn out from under the floor

The sump is a small chamber under the slab with a pipe to the outside. If radon levels are high, a fan can be added to suck the gas away.

Other Construction Studies topics

All of Leaving Cert Construction Studies