Finding an honest damp-proofing firm

[Adam Funk]

Aren't those usually dark blue or bluish-black bricks?

(Maybe there's a less obvous kind that I haven't noticed!)

[charles]

Known as "Engineering Bricks". I believe there can be red ones, too. It used to depend on what a local brickworks produced.

[Adam Funk]

That's what I thought.

I didn't know there were red engineering bricks, but maybe they are just close enough not to be noticeable to a non-expert.

[Steve Walker]

These aren't.

They are presumably some sort of impervious, engineering brick, but as the bricks used for the walls have the same smooth, darker-red look as many engineering bricks (although they are not), you can't tell where the transition is.

[Adam Funk]

Interesting, thanks.

[PeterC]

I don't have a damp-meter but my multi-meter, om 20Mohm range, shows low resistance where there's very obvious dampness and OC just above that line. I don't know how a proper meter works.

In my friend's house all of the joists are below DPC. I'll have to take up some boards in the front hall (no carpet and no furniture) and have a look. I'm not taking up the concrete to look!

[Chris Bacon]

That's a decent plan. You might find there's just a lack of airflow (e.g. airbricks or vents are clogged/covered).

Photos?