Can damp cause raised markings..like these?

Cinquestelle

Can anyone please help diagnose what is causing unsightly marks on my walls? They are basement walls and raised marks appear near the floor level. I normally sand them down and repaint, but after a few months they reappear. Elsewhere on the walls the encrustations appear as small hard raised dots.

A little while ago I repaired two large dents with Polyfilla only for encrustations to appear all around the borders of the filler. I remember the Polyfilla dried a brownish colour.

The walls do not feel damp but could this be the underlying cause nonetheless? Is there anything I can do that is not too brutal, something that can hold it back for a few years at least until the next decorating round? Applying a coat of PVA has been recommended to me but if sealing the wall was the objective I would have thought using a propriety damp seal paint would be a better bet. I would be grateful for any advice.

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Unfortunately I am not being allowed to post my photos (pity, they took an age to prepare and link via photobucket and a picture is worth a thousand words and all that). Any thoughts still appreciated.

iamcornholio

Just by the description, blistering and brown stains are indicative of water penetration - the moisture is pushing the surface coating off

No paint will suffice, you will need a proper liquid membrane coating before the finish coat.

But the problem may be that the damp , in time, moves around and small patch repair

anotherbaldrick

This probably means the damp proof membrane is defective , or in a Victorian or earlier house you do not have a damp proof membrane in the wall at all.
But fear not, a specialist will be able to drill and inject a damp proofing substance to cure all. Choose one who will give you an independant guarantee

Leif

anotherbaldrick wrote: »

This probably means the damp proof membrane is defective , or in a Victorian or earlier house you do not have a damp proof membrane in the wall at all.
But fear not, a specialist will be able to drill and inject a damp proofing substance to cure all. Choose one who will give you an independant guarantee

I assume a basement is below ground in which case would there be a damp proof membrane? I know there are difference ways of building basements there days, including the fully sealed kind.

I wonder if condensation could be an issue? If damp air is descending into the basement, and the floor and walls are cold as they are in contact with the ground, then perhaps that is an issue? I mention this because I have a mild form of this in some cupboards in areas close to heating pipes. I am not quite sure how it happens in my case.

Cinquestelle

iamcornholio wrote: »

Just by the description, blistering and brown stains are indicative of water penetration - the moisture is pushing the surface coating off

No paint will suffice, you will need a proper liquid membrane coating before the finish coat.

But the problem may be that the damp , in time, moves around and small patch repair

Hi, thanks for the reply. I was wondering what you mean by "proper liquid membrane coating". Do you not mean something like Polycell Damp Seal, that I allude to and which goes on like paint?

Cinquestelle

anotherbaldrick wrote: »

This probably means the damp proof membrane is defective , or in a Victorian or earlier house you do not have a damp proof membrane in the wall at all.
But fear not, a specialist will be able to drill and inject a damp proofing substance to cure all. Choose one who will give you an independant guarantee

Thanks for the reply. I agree with you about the damp proof membrane possibly being absent. The property is Edwardian!

macman

OP, keep posting and you will be allowed to link sites.

Cinquestelle

Leif wrote: »

I assume a basement is below ground in which case would there be a damp proof membrane? I know there are difference ways of building basements there days, including the fully sealed kind.

I wonder if condensation could be an issue? If damp air is descending into the basement, and the floor and walls are cold as they are in contact with the ground, then perhaps that is an issue? I mention this because I have a mild form of this in some cupboards in areas close to heating pipes. I am not quite sure how it happens in my case.

Hi, thank you for replying. I will give that some thought, but having revealed the foundations are rather old, I guess you may well veer towards the DPM being deficeint or non-existant.

Unfortunately I am not in a position to spend a great deal of money on the problem and its only affecting a relatively small area of the wall after all, a corner if you will. It would be great if there was some measure that could mask it for a time; that’s why I brought up the question of Damp Seal paint.

But then there is the issue of which type of damp seal coating! The one that is microporous like Ronseal Thompson’s (which seems like a contradiction in terms) and Polycell’s Damp Seal which I gather is minimally microporous. The more I try to avoid brutal professional action, the more complicated it gets!!

iamcornholio

Cinquestelle wrote: »

Hi, thanks for the reply. I was wondering what you mean by "proper liquid membrane coating". Do you not mean something like Polycell Damp Seal, that I allude to and which goes on like paint?

I'm not familiar with that Polycell product. It may well do the job but it may not be suitable for sealing basements as the water tends to push through with more pressure, and so you need to read the tin or ask for advice from the shop

What you need is something more than paint, and it is normally either a bitumen or other rubber based liquid and has good adhesive qualities

Something like this one from Wickes, but the thing to look for is the "liquid damp proof membrane" bit and look for "suitable for basements" which would be important

Cinquestelle

Thank you iamcornholio. I appreciate the link. I have never seen this product before and will definitely take a closer look.