Tanking a basement
You will see this word in searches and on imported guides. It describes a real approach, but not every house suits it.
Tanking a basement means lining the walls and floor with a waterproof layer so the space acts like a sealed tank. The word is mostly British. In the US you will usually hear interior waterproofing membrane, coating or sealed liner instead.
This page prints no prices. It explains the idea so you can judge it.
What tanking actually is
The idea is simple. A waterproof layer goes over the inside of the walls and the floor, and the layer is joined at the corners. Water that reaches the wall is held back by the lining instead of entering the room.
Compare that with a drain system. A drain accepts that water arrives and moves it to a pump. Tanking tries to stop it at the surface. The waterproofing from the inside page covers the drain approach.
Where it falls short
Water outside a wall can press hard, especially when the soil stays saturated. A lining on the inside has to resist that pressure and stay stuck to the wall. If it lets go, water gets behind it and you may not see it. Take a position: tanking alone is a weak plan for a basement with ongoing groundwater.
It also does nothing for a cracked or moving wall. The foundation coating page shows the same limit for thin layers.
Where it makes more sense
- Light dampness where the outside has already been fixed.
- A space with no live groundwater pressure.
- A plan that pairs the lining with drainage and a pump.
For deeper problems, the interior vs exterior page compares the real options.
Do the outside first
Lengthen the downspouts. Clear the gutters. Slope the soil away from the wall. Many basements improve before anyone lines anything. Watch the wall through a heavy rain, then decide.
Ask the right questions of anyone selling it
Ask what happens when water pressure builds behind the lining. Ask whether a drain and pump are part of the plan. Ask for the answers in writing, and compare more than one proposal.
Local rules and structural limits
Codes and permits vary by state and town, so ask your building department. A wall that leans, bows or has long horizontal cracks is structural. That belongs to a licensed structural engineer, ideally one who is not selling the repair.
Frequently asked questions
What does tanking a basement mean?
It means lining the inside walls and floor with a waterproof layer so the basement acts like a sealed tank. The term is mostly British.
Is tanking the same as basement waterproofing in the US?
It is closest to an interior membrane or sealed liner. Most US plans lean on drainage and a pump rather than a lining alone.
Can tanking stop water under pressure?
Only if the lining stays bonded to the wall. If it lets go, water can get behind it, so it is a weak plan on its own where groundwater is persistent.
Does tanking fix a cracked wall?
No. A cracked or moving wall is structural and needs a licensed structural engineer.
What should I do before tanking?
Fix gutters, downspouts and soil slope first, then watch the wall through a heavy rain before deciding on anything inside.
Sources
What this page explains is based on these official sources. If you check one and it does not match what you read here, send it to us and the article gets corrected.