Can anyone recommend the best stain block for salt damp?

[kkudi]

I recently had my 3 bed house redecorated and some damp patches have appeared on the flank wall downstairs.

I had a damp specialist (quite well known) come round and he said that the damp I have is what's commonly known as salt damp and that replastering would fix the problem on the inside - there's some work to be done on the outside (broken plinth at wallbase in neighbour's garden) as well as install a gutter on the neighbour's shed as the shed is massive and all the rainwater goes splashing onto my side wall.

The house is end of terrace but sadly there's no side access because of the neighbour's gardens (2 of them) bordering the side wall.

While all the external work will be addresses ASAP, I'm in no position to spend apprx £3000,4000 to replaster the entire side wall at height of 1.2m .

He advised that as a temporary fix (12-18months) a stain block could be used.

So doing a bit of googling around hasn't helped much with stain block and salt damp so here I am asking for advice which is the best one to buy for this type of 'damp'.

Thanks

 

[footprints]

How about Pepper Spray!
Seriously though you don't want to trap damp in the wall and any sealer will do that, Zinsser products are good, bulls eye 123 is a good one they make, but I would advise against it as stain blockers are to designed to "lock in" the stain if the wall is still damp they will peal just like any other paint.

 

[misterhelpful]

The term 'salt damp' is new to me but I assumed it to be another way of describing efflorescence (a whitish crystallised blooming and blistering of the surface) caused by damp. After googling the term it appears that I'm right, so presumably this is what you have?

The problem you have isn't uncommon but can be difficult to remedy. The starting point is to address the source of the damp which means repairing the exterior of the wall. Until this is done, there is no real point in doing anything internally as it won't work and is highly unlikely to last even 12 months. The wall has to be free of penetrating moisture because the cycle of being wet and drying out is what pushes the salts (caused by high alkali levels in the plaster/cement) to the surface of the wall.

Once the wall is repaired, you must allow it to dry out thoroughly, which will allow the majority of the salts to come to the surface, before brushing or scraping them away without using any moisture. However, even then there is likely to be some residual salt that will still try to surface so it is always best to apply a coat of alkali resisting primer to the internal area before doing any filling and/or painting.

If you do have efflorescence, I don't see much point in using a standard stain block as it has no properties to stop the blooming. Bullseye, mentioned by footprints, does have alkali resisting properties, but it must be the 1-2-3 Plus version and not just the standard 1-2-3. That said, it still won't have much of an effect on a surface that still has issues with moisture penetration, and neither will a damp seal product.