Many York basements are built with hollow concrete block walls. Those hollow cores connect to the soil and can carry radon up and into the basement. When slab suction alone is not enough, a contractor may add block wall suction. This guide explains when and how it is used. Read on for the details that matter most.
What is block wall radon suction?
Block wall radon suction draws soil gas out of the hollow cores of concrete block foundation walls. A pipe connects to the wall cores, usually near the floor, and a fan pulls air from inside the blocks. The tops of the walls and large openings are sealed so the fan pulls soil gas, not basement air. In York basements, it is often added when slab suction alone does not lower radon enough.
How Block Walls Carry Radon
Concrete blocks have hollow cores that line up vertically. When the wall is built, those cores create a network of open spaces running from the footing to the top of the wall.
Soil gas can enter the cores through cracks, mortar joints, and the bottom of the wall. From there, it can move up and out through openings in the blocks, gaps at the top of the wall, or holes around pipes and wires.
Because the cores connect, a block wall acts like a series of chimneys. That is why some block foundation homes still have elevated radon after a sub-slab system is installed. The slab is covered, but the walls are still bringing radon in. A short visit usually answers most of these questions for your particular house.
When Block Wall Suction Helps
Most block basements get a sub-slab system first. In many homes, slab suction also pulls some air from the block cores and is enough by itself.
When a retest is still high, the contractor may look at the walls. Pressure readings or smoke tests can show whether air is moving through the blocks.
If it is, block wall suction can be added. The contractor drills into the block cores, usually near the floor, and connects them to the radon pipe. The tops of the walls, open block cores, and large gaps are sealed so the fan pulls from inside the wall. Sometimes several walls are connected to the same fan. A few minutes spent on this step often prevents a return trip or a second round of adjustments.
Sealing and Checking Results
Sealing makes block wall suction work. If the tops of the walls are open, the fan pulls basement air through them instead of soil gas. The contractor caps or seals open cores and fills large holes around pipes.
This sealing can take time in an unfinished basement with many openings, and may be harder in finished areas where the wall tops are hidden.
After the change, the gauge should still show good suction. Retest under closed-house conditions after the system has run at least a full day. If radon drops, the added suction is doing its job. If not, the contractor can look for remaining leaks or other paths. If anything here is unclear for your home, the written quote is the right time to ask.
When the Walls Need Attention
Block walls can be a hidden radon path, but they can be addressed. If your York block basement still tests high after a slab system, call us and we will connect you with a local contractor who can check the walls and explain whether block wall suction makes sense. Knowing the steps ahead of time takes much of the stress out of the process.
Frequently Asked Questions
Does every block basement need wall suction?
No. Many block basements reach low radon with sub-slab suction alone. Wall suction is usually added when a retest shows the slab system is not enough and testing points to the walls. The contractor can confirm the details for your home during the free on-site visit.
Can block wall suction be done in a finished basement?
It can be harder, since the wall tops and cores may be covered. The contractor may access the walls from an unfinished area or through small openings. They will explain the options during the estimate. Ask about it during the visit so the answer is based on your actual home.
Will drilling into block walls weaken them?
Small holes drilled into block cores for suction do not compromise the wall when done correctly. The contractor places them carefully and seals around the pipe connections. The answer can change from one house to the next, so an on-site look helps.