Is this Hygroscopic salts?

markmcvit · 12 Jun 2020

1910s victorian mid terrace here.

I've got a damp room downstairs, the symptoms of damp are showing up on the chimney breast and the bottom of the walls either side of it.

Here are some pics I've taken, I think its salts causing this on the walls, rusting the plaster beading, flaking some of the paint and rotting the skirting boards. But what has thrown me is that this morning the floorboards in one corner, which werent even touching the wall have got wet. Cant figure out why

Any one able to say if its salts for sure?

And if so, I think I'll go down the route of salt neutralising solution, batten leaving a small gap and plasterboard/skim over?

Thanks

^woody^ · 12 Jun 2020

The wall is more likely to have a rising damp problem than a salt problem. A neutralizing solution won't cure any damp problem.

catlad · 12 Jun 2020

If this is your own house and want it to last then you will need some of that egg box stuff to line the walls with first.
Sorry can't remember the name, its a type of damp proof membrane.

markmcvit · 13 Jun 2020

Thanks guys, not sure its rising damp as its not damp below the floorboards, just on that line across.

^woody^ · 13 Jun 2020

Hygroscopic salts can't get in to brick walls unless transported by ground water

dontbelieveawordofit · 13 Jun 2020

youll be wasting your time ‘neutralising’ something if your planning on battening it. make sure you have dpc behind your battens and the underfloor and void behind the wall is well ventilated.

^woody^ · 13 Jun 2020

dr dolittle said:
Is rising damp a thing?

Call it what you like, if the bottoms of walls get damp and it moves upwards, then it's rising damp.

^woody^ · 13 Jun 2020

dr dolittle said:
How does water travel upwards then?

I don't know, ask an Australian.

Perhaps everyone should start leaving DPC's out from now on as it's all a massive con, and every building inspector is wrong.

markmcvit · 13 Jun 2020

@bennymultifinish I'll do that, sounds like the easiest option I've found from my research!

And yea, I've been watching a lot of Peter ward videos on YouTube, he's convinced me rising damp isn't as common as it's made out to be.

dontbelieveawordofit · 13 Jun 2020

there has to be a % of moisture in old buildings .
is rising damp a thing? probably .
is it as bad as some people claim it to be ? probably.
is it not as bad as some other people claim it to be ? probably.
are the majority of people who claim to know all about it peddling products and services? definitely.
the solution you devised for yourself is as good as any.

tony1851 · 13 Jul 2020

dr dolittle said:
How does water travel upwards then?

Capillary attraction.

Munroast · 13 Jul 2020

dr dolittle said:
How does water travel upwards then?

capillary action - dangle a tissue in a cup of water and watch the dampness rise up it.

with stone walls it rises up 2 or 3 foot

we had a problem wall in an old house we lived in, I hacked the plaster off to waist hiegt, pointed the wall up, painted it with bitumen, blinded it, plastered it and the job was a good'un

JohnD · 13 Jul 2020

dr dolittle said:
How does water travel upwards then?

capillarity

Which is also why it doesn't rise up many courses of clean, unplastered, unrendered, cement-mortar brickwork, because the pore size in the mortar and the bricks is different, and it doesn't easily move from large pores to small.

In my house (outdoor walls below DPC) it only rises one brick, then stops dead.

JohnD · 13 Jul 2020

markmcvit said:
chimney breast

Open up the fireplace and dig out all the old rubble. Dig out the hearth as well. The damp is rising up the rubble that the builders threw in.

Leave it open for a week (with the chimney ventilated at the top) and you will see the damp reduce as it evaporates away.

When you brick up the fireplace again (or you can leave it open as a niche, ornamental feature, or put a wall-safe or wine rack in it) be sure to include an airbrick or other ventilation so air can flow up the chimney and escape, carrying evaporated moisture with it. If you want, you can leave it open into the subflooor void.

Disused chimneys must be ventilated top and bottom.

While you have it open, look for and remove any redundant pipes, such as for an old back-boiler. Rarely, they are still connected to water.

While you have the floor up, clean out all the air bricks (there may be insufficient). If any have been blocked by idiots raising paving or flowerbeds against the wall, correct this error. There is quite a good chance that your house has a slate DPC, which will work if allowed to.

JohnD · 13 Jul 2020

btw, scrub those floorboards and rinse off. A peeing pet will lead to a buildup of salts which can attract moisture. Often seen in converted stables and cowsheds.

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Is this Hygroscopic salts?

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