Damp Protection for Internal Walls, in the Right Order

Done properly, damp protection for internal walls works from the base upwards. So before a board or a tin of paint comes near the room, check the wall. Find out whether the masonry is drawing water out of the ground. A finish laid over a wet wall lasts one season.

An internal wall picks up damp from three places: the ground below, a nearby leak, or the room air. Each one calls for a different answer, and damp protection for internal walls means treating the right one.

Where damp protection for internal walls really starts

Brick, stone and mortar are full of microscopic channels, and water climbs them as it climbs a paper towel. The narrower the channel, the higher it goes, an effect known as capillary action. Our article ATE: electromagnetic anti-damp device for damp walls and rising damp traces that climb from the footings up.

At the surface the water evaporates and leaves its salts in the plaster. They crystallise, they swell, and they crumble the render from within. That is why a wall looks sound in June and blisters in November. Those crystals also draw moisture out of the air. So ATE or ATG: which Humidistop device to choose against damp walls is worth reading first.

The tide mark tells you most of what you need. Low and steady means the ground. High and spreading after rain means the outside face, while beads on the coldest corner mean the air. Our article Rising Damp: Signs, Causes and Solutions sets out the signs.

Why dry lining rarely counts as damp protection for internal walls

Plasterboard on battens hides the mark within a day. Yet the water carries on climbing behind it, and the salts carry on growing. So the battens sit in the damp zone for years.

Then an internal waterproof membrane behaves the same way. It moves the wet face further back into the wall. Then it sends the damp higher up, often into the floor above. Neither approach counts as damp protection for internal walls, and both make the next repair harder.

A renovating lime render is more honest work. It holds salts in its thickness and lets vapour out, so the wall keeps drying while it looks presentable. Even so, that is one layer of damp protection for internal walls rather than the whole job.

Treating the masonry itself

The ATE is an electromagnetic polarity inverter. It plugs into an ordinary socket and sends very low frequency electrical pulses through the masonry, continuously. Its design principle comes from electro-osmosis. The pulses act on the electrical charges where the water meets the wall of the pore. So they work against the climb and favour the return of the water towards the footings.

That is a design principle, and we present it as nothing more. The unit takes no water out and adds no heat, so the wall dries by ordinary evaporation. Visible results come between 18 and 24 months, and a thick stone wall sits at the slower end.

So damp protection for internal walls means patience. The ATG follows the same principle as a geomagnetic polarity inverter, with no supply at all. Our guide Damp Wall Treatment: Which Solution Should You Choose? compares the two ranges.

Choosing the model that covers your walls

Each unit works over a radius, measured from the point where you fix it. So measure the walls you want to treat, then pick the model whose radius covers them from a central position.

Model	Range	Price
ATE LC15	7.5 m radius, 15 m across	€1,290
ATE LC30	15 m radius, 30 m across	€1,590
ATE MAX	30 m radius, 60 m across	€1,990

Every unit draws 0.75 W on a 12 V supply and measures 322 x 232 x 32 mm. Each one carries a 10-year manufacturer warranty. All three are made in France, and delivery costs nothing. The ATG follows the same design principle with no mains supply, which suits a wall with no socket within reach.

Fitting the unit yourself

Fix it to a load-bearing wall or a partition wall, between 30 cm and 1 m above the floor. Aim for the centre of the area to treat. Two wall plugs and a socket, less than an hour, no tradesman.

Never fix it to plasterboard and never to insulation. The back of the unit has to touch the masonry. Keep 1.50 m between the unit and any other electrical equipment.

If the bottom of the wall carries a waterproof cement render, cut that render back over ten centimetres or so. Then the water reaches the air and evaporates, instead of sitting trapped behind a sealed skin.

The finishes that matter for damp protection for internal walls

Once the wall has dried, keep every layer vapour-open. Lime plaster, mineral paint and a breathable render let the masonry release what it still holds. A plastic emulsion traps it instead. Our guide ATG Geostop: the standalone unit that installs without an electrician runs through the choices.

Leave a gap behind wardrobes on any wall that has been damp. Air moving across the plaster does half the drying. So a sealed pocket in a corner undoes much of the work.

Watch the outside as well, because damp protection for internal walls fails if the ground keeps feeding it. A path raised above the internal floor level will beat any treatment. So will a blocked air brick, or a downpipe discharging at the foot of the wall. If a building site does not appeal, Resin injection cost: is there an alternative? sets out the route that leaves the room intact.

Frequently asked questions

Can I dry-line an internal wall to hide the damp?

Dry lining hides the mark, and the water keeps climbing behind the boards. The battens then sit in the damp zone, so the repair grows each year.

Does a waterproof membrane on the inside work?

An internal membrane pushes the wet face deeper into the wall. Often it sends the damp up to the floor above. That is concealment rather than damp protection for internal walls.

Where should the unit go for damp protection for internal walls?

Fix it to a load-bearing wall or a solid partition wall, between 30 cm and 1 m above the floor. Keep it 1.50 m away from other electrical equipment.

How much electricity does the unit use?

The ATE draws 0.75 W on a 12 V supply, which is less than a night light. The ATG uses no supply at all.

What area does the ATE MAX cover?

The ATE MAX works over a 30 m radius, so 60 m across from a central fixing point. One unit then covers most houses.

Before you order

The unit treats rising damp and capillary damp, and nothing else. It does nothing for a leaking gutter, for driving rain, or for poor ventilation. Those three causes together remain more common than capillary damp, so rule them out first.

Rather than guess, send us two or three photos. One of the bottom of the wall, one of the room, one of the outside face. We read them and tell you which model fits, or tell you plainly that your problem lies elsewhere.

See the ATE and ATG models · free delivery, 10-year warranty, made in France