Curing Damp Walls with Plascon Dampseal

Curing Damp Walls DIY Guide by Donovan Bezuidenhout

As with any damp issue, one must always find the source of the damp first before you can proceed with curing damp walls. Consumers tend to “paint over” or “fix” the paint problem but not the actual damp problem. This causes further problems as the constant supply of moisture is then diverted and migrates to wherever it is able to. Plascon Dampseal is unique in the way in which the product reacts with the moisture in the surface forming an impenetrable barrier through which the movement of water and dissolved salts is not possible. The salts are found in the cement plaster, and when damp, these salts get trapped beneath the paint film and cause the paint to discolour and lift.

Curing Damp Walls: Finding the Source of the Damp

Curing Damp Walls with Plascon DampsealIt would be of value to know where the damp in a wall is occurring, lower wall or middle wall and whether the other side of the wall is interior or exterior. If interior, what room is on the other side, such as a bathroom? If exterior, are there pipes running in or on the walls? Are there taps and gully’s? Is it a North-West facing wall (driving rain side)? Is there a garden with an irrigation system close or next to the wall? Is the water (if any) able to run-off easily and is the level of soil higher than the floor level of the kitchen? If the damp is occurring closer to the ceiling, then there are possible roof or parapet wall leaks.

I suggest you scrape the existing paint off the affected area first, down to the plaster. If the plaster is very dark grey in colour, then the wall is excessively wet. If so drill holes into the plaster to allow moisture to escape and place a fan close by if possible. Fill holes with exterior Polycell Polyfilla and not interior Polyfilla as it is gypsum-based and water sensitive. If the plaster is light to dark grey then you can proceed with the Dampseal application.

Curing Damp Walls DIY Guide

Divide the affected area into 3 horizontal sections with the top section extending at least 30cm above the affected area. Ensure that the area also extends by 30cm to the left and right of the affected area. Treat the lower section by applying a thinned coat of Dampseal (3 parts Dampseal to 1 part turpentine in volume) and allow 24hrs drying and curing time. Repeat the process for the middle section and the top section with 24hr intervals. After 3 days of application of the first thinned coat to each section, apply the second coat to the entire section and allow 24hrs drying and curing time. If using a water-based / acrylic paint you may apply the coatings directly onto the Dampseal.


  • Donovan Bezuidenhout is a training practitioner for Kansai Plascon.

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70 thoughts on “Curing Damp Walls with Plascon Dampseal

    • Hi Kobus, Aluminium Carbomastic 15 is a product manufactured by Carboline. Please contact us on 0860 20 40 60 for a similar product and industrial advice.

  1. Hi

    I had a pipe leak on the hot water line in the wall and found the walls damp, covered in mould and the paint flaking. I need info what to do.

    • Hi Ravi, see below for some more info from our advisory service.

      Please remember that the moisture problem must be resolved and the wall allowed to dry completely before commencing with the following advice.

      Fungal and algae growth:

      Scrub the affected area using a solution of household bleach mixed 1 part bleach to 2 parts water. After 1 hour or marked colour change (lighter), brush clean using a hard bristle brush. Then rinse thoroughly with fresh water to remove all traces of bleach and allow it to dry completely. Please remember to protect your hands and eyes when using bleach.

      Remove loose and peeling paint back to a firm edge by scraping, sanding or using any other suitable means. Feather the edges with 100 grit sandpaper and ensure the surface is dust free. Please ensure all surfaces to be worked on are completely clean, dry and sound.

      You can apply Plascon Dampseal to bare and exposed areas. Thin the first coat 3 parts Plascon Dampseal to 1 part Mineral Turpentine by volume and allow it to dry for 24 hours. Apply 2 more unthinned coats to these areas with 24 hours drying time in between coats.

      Plascon Dampseal may be over-coated with a good quality emulsion or enamel paint. If over-coating with an enamel, first prime with Plascon Plaster Primer.

      Please find the Dampseal technical data sheet here and refer to the surface preparation, application and caution sections or contact our Advisory contact centre on 0860 20 40 60.

    • Hi Jacques, thanks for getting in touch.

      The membrane is used to form a waterproof barrier on the surface. It becomes hard and prevents water and moisture from seeping into the cracks or holes on the surface.

  2. Good Day, Please assist if possible. I am working in a new hotel here in Lagos, Nigeria. High humidity levels. I need to know if you have a supplier of your products in Lagos? I am looking for Plascon Dampseal. Also there is dampness beginning to show through the wallpaper in the bedrooms. Can Damseal be applied over wallpaper? Urgent please.

    • Hi Paddy, thank you for contacting us.

      Please note that Dampseal cannot be used over wallpaper. It needs to go on bare plaster or cement. Will also regret to inform you that Plascon products are no yet available in Nigeria.

  3. Hi. I live in a downstairs house. Above me is my landlords balcony. I have dampness right through my house from the wall to the ceiling. Can Damp Seal help me? If not, is there any other product that I can use to seal my landlord’s entire balcony? It’s quite big.

    • Hi Nicholas, thanks for getting in touch.

      Unfortunately you will need to contact waterproofing specialists like Coprox as we do not have a product that can be used on such a surface. Dampseal is for rising damp and penetrating damp (occurs to 1.1m above the ground level).

  4. Hi, My Kitchen cupboards are mouldy inside due to the water leak in the bathroom (I am told). The wall of my kitchen units is the same wall as the bathroom where the bath is situated. I cannot store anything in these cupboards. From the surface top to the floor, this cupboard is useless. How can I get rid of the mould and be able to use this cupboards? Please help as I am running out of space in the kitchen!!!

    • Hi Rufaida, sorry to hear about your mouldy cupboards! As you can see from the Q+A’s above, one first needs to find the source of the damp and have a professional seal this properly. As far as protecting the surface from future leaks thereafter, Dampseal is exactly what you need.

      Please see the links for Dampseal Surface Preparation Guide and our step-by-step guide to Curing Rising Damp. There is also more info on our FAQ page. Please don’t hesitate to get back in touch if you are still unsure of anything!

  5. Can I paint Dampseal over old paint, or does it only stick on raw plaster? I have scraped off all the loose / flaking paint, so there are patches of paint and raw plaster. Will Pascon Dampseal adhere to this??

    • Hi Jon, unfortunately we can’t specify a price as different retailers have different markups and prices are subject to change. Best to check at your nearest retailer that stocks Plascon products.

  6. Live in edwardian mid terrace house, had replastered down to brickwork 12 years ago, now getting one damp wall adjoining next doors kitchen. How can I stop damp penetrating please? Just sanding off the surface as the wall is “pimply” and we have a damp line about two feet from ceiling.

  7. Hi there,

    I have penetrating damp from the shower in the adjacent room. I have fixed the source of the leak.

    I was wondering if I had to wait until the damp wall was 100% dry before I applied the damp seal or could I just scrap off the old paint and go for it as is?

  8. I am applying Sikalite to my plaster outside. Product is mixed with cement & plaster sand. I also have Dampseal. I want to know if I can put the Dampseal on after the Sikalite and if so, without thinning it out.

    • Hi Louise, thanks for getting in touch.

      We recommend that you rather confirm with the manufacturer of Sikalite if the product will be compatible with Plascon Dampseal. We don’t think it should be a problem because the dampseal is designed to be applied over bare plaster, however it has never been tested with Sikalite so we cannot guarantee if the two will be compatible if used together.

      First coat of Plascon Dampseal has to be thinned. Please find attached Technical Data Sheet for the product.

  9. I have a problem with damp and mould in my bedroom. I’m in the process of solving the cause. However i need to know how I can mend the problem inside using your products. The paint in the bedroom is not peeling off. Rather the mould is just over it. Should I simply clean the surface with sugarsoap and mould killing products and then apply damp seal without scraping the paint ?

    • Hi Senzo, thanks for getting in touch. Here’s what you need to do:

      1. Clean the surface first with a bleach and water solution.
      2. Clean a second time with a new bleach & water solution. This kills the negative & positive spores of the mould.
      3. Clean with Sugar Soap, then rinse off with clean water.
      4. If paint is not loose and peeling, then sand surface lightly and wipe dust off with a clean dry cloth.
      5. Apply Dampseal according to instructions in the attached Technical Data Sheet.

  10. Hi

    I see that Dampseal can be used for interior uses as well. I do not necessarily have damp/leakage problem, but my bathroom wall gets wet from the shower.

    Would Dampseal help to keep the moisture from seeping into the wall? I’m looking to paint my whole bathroom with Dampseal, walls and ceiling. Someone also recommended that I use Roofseal, but not sure if this would be recommended?

    I know that you guys have kitchen and bathroom paint that would be more suitable for this purpose, but I am renting at the moment and do not want to spend as much. So basically, I’m looking for a good cheap alternative.

    Advice would be appreciated.


    • Hi Tiaan, thanks for getting in touch and we appreciate your concerns.

      We wouldn’t however recommend Plascon Dampseal for your purposes. Please note that Dampseal is a product designed to treat the effects of rising and penetrating damp only, and we do not recommend using it to waterproof bathroom areas. Plascon Kitchens & Bathroom (or Plascon Velvaglo) are the only products we recommended using for such an area.

      Please also note that we do not have a full waterproofing system from the Plascon Range. Should you require a waterproofing solution, you can contact a company called Coprox on 011 579 4300 as they deal with waterproofing.

  11. Why can’t I apply this product (Plascon Dampseal) with a roller? Painting with the brush (I am an amateur) results in a very thick layer everytime.

  12. I have applied Dampseal to a limited area on a wall where the damp was seeping through (as per instructions) but where I painted over there is a marked difference in paint colour over the sealed portion! Help

  13. Hi there,

    We have sorted out the dampness problem & was wondering can you paint Plascon Double Velvet over the Dampseal treatment?


    • Hi Tarryn,

      We recommend that Plascon Dampseal rather be overcoated with a good quality emulsion or enamel paint. If overcoating with an enamel, first prime with Plascon Plaster Primer.

  14. Hi, I am living in a flat and the ceiling is concrete. We have been living there for the passed 5 years and now the paint is starting to flake off. Can I prepare the ceiling and use Dampseal, or is there any other product I can use? Thanks

    • Hi Kamal, thanks for getting in touch with us.

      Please note that Dampseal should only be used if you have a damp problem. If there is a damp issue on the ceiling you will first need to find the source of the damp and fix it.

      If there is no damp problem then you will need the sand / scrap off the old paint and then apply 1 coat of Plascon Bonding Liquid followed by 2 coats of Plascon Polvin Walls and Ceilings.

  15. I have a lot of moisture in the air and it is making my walls very wet to the point that I see droplets running down the walls (condensation + humidity). I want to sort this problem out. Would Dampseal help with this and is it something I can do myself or do I need to get a professional in to assist? Basically my builder has done a shoddy job and is not prepared to assist as he says he has damp-proofed the place. I don’t believe him. All he did was plaster the walls and put a white paint over and that is it. This is only happening in the areas where he built on. I have added more ventilation but not sure if that is working. I am at my wits end cos the air is heavy and I want to prevent damage to the walls. Thank you

    • Hi Alison, thanks for reaching out to us. While Dampseal will certainly help, it’s important to address the source of damp. You would need to consult with a specialist regarding this. We suggest giving Coprox a try. They can be contacted on 011 579 4300.

  16. Good day, the rooms in my house are damp, mould rooms are dark. I don’t know the cause. Each year I am painting the house. Can I use Dampseal and which other waterproof paint I can use on the outside for water not to penetrate on the inside? Most of the houses in my area experience the same problem. Thanks

    • Hi Nontando, thanks for connecting with us. You can use Dampseal for rising damp that is not more than 1 meter above ground level. After applying Dampseal you can finish with any chosen top coat. To kill the mould, try using 1 part bleach to 2 parts water to clean the walls.

  17. Hi Plascon,

    We have purchased a house in Riversdale in the western Cape. It has not been painted or maintained for over 12 years. It seems like there is rising damp in nearly every room, as well as descending damp on the walls facing the direction of the rain. Where do I start? My thought was to do the top of the walls on the outside and then work down. The same with the interior. How do I know if my “damp course” has failed? Can I drill holes in it to see if moisture comes out, or are they merely ventilation holes?

    Thanks for a most informative site.


    • Hi Mike, thanks for getting in touch and for your compliment!

      Please note that while Dampseal will certainly help, it’s imperatively important to first address the source of the damp; otherwise you will likely experience endless issues.

      While Plascon does not have a full waterproofing solution, we can however recommend contacting a company called Coprox on 011 579 4300 who do offer such.

      Note: Dampseal should only be used for rising damp no more than 1.1m above ground level.

  18. Hi, do you by any chance have a branch in East Africa please? I need to treat a rising damp on a standing block wall. Please advise. Thanks

  19. Hi, I have rising and penetrating damp in a number of walls in a ground-floor apartment I own. I want to treat the areas with Damp Shield, however, I noticed that the walls have been skimmed with cretestone, which I assume is gypsum-based. Does the cretestone need to be removed before the damp shield can be applied? I hope not, as this is a major job!

    • Hi Rijk, thank you for inquiring with us.

      Yes, unfortunately you will need to completely remove the cretestone before applying Dampseal (I’m assuming you meant “Dampseal”)?

      If you do not want to tackle removing the cretestone yourself, there is a company called Coprox (011 579 4300) who will be able to assist you / recommend a product to use.

  20. Hi, I have a damp problem on the inside of an exterior north facing wall. 2nd floor under the window and 1st floor under the window. Would damp seal be a solution? If not, could you please offer further guidance. Is the alternative to strip plaster on external wall and apply membrane between window and brickwork? Thanks Daryl

    • Hi Yanda, please note that Plascon does not offer a full waterproofing system. You would need to contact a water-proofing company to fix the leak before applying any Plascon products.

  21. Hi there, I have paint peeling off the walls outside my house in quite a few places. Some places are not near pipes or any other water source and the house has no gutters, so I think it’s mostly rain water running down the walls. If I scrape the paint off and allow to dry as best as possible, will Plascon Dampseal solve my problem and stop it coming back or would I need waterproofing? Thanks

    • Hi Matthew, thanks for connecting. Here’s what you need to do:

      1. Ensure that surfaces are clean and sound before painting. Surfaces may be slightly damp, but not wet.

      2. Remove any paint completely back to the bare substrate and remove loose and friable material to achieve a sound surface. Re-plaster with cement plaster if necessary.

      3. Remove any oil and grease with Polycell Sugar Soap.

      4. Rinse thoroughly, and apply 3 coats of Plascon Dampseal, allowing 24 hours drying time between coats,
      Only thin the first coat with 3 parts Plascon Dampseal to 1 part Mineral Turpentine by volume.

      Note: Plascon Dampseal may be overcoated with a good quality emulsion or enamel paint. If overcoating with an enamel, first prime with Plascon Plaster Primer.

  22. Hi there. In preparation for using Dampseal, we used paint stripper on an interior wall. We have tried everything we could think of, but the smell is not improving much. Now we are afraid of applying the Dampseal, thinking that it may ‘lock’ in the paint stripper smell forever. Is it safe to go ahead?

    • Hi Marick, thanks for connecting with us. Marick please can you advise us which paint stripper you used? Our RemovAll All Purpose Paint Remover has a low odour and is an environmentally friendly, water-based & fully biodegradable product. Unfortunately we are not sure on other paint strippers and the only recommendation we can give is proper ventilation.

  23. Good afternoon, I have a cottage where we had a leaking pipe which flooded out the entire cottage. We waited a few months to have the kitchen cupboards redone. The cabinet makers seemed happy that the walls were dry enough, but recently I have noticed that the walls are peeling and continue to be damp. Unfortunately accessibility is limited because the cabinets are fairly small and difficult to get into. There are no further leaks from inside or out. Will your Plascon Dampseal help once we have cleaned off the old paint? Why would they continue to be damp? I do live at the coast. (Silly question)

    • Hi Denise, thank you for reaching out to us. Here’s what you need to do:

      1. Allow the walls to dry out after all the paint had been stripped off.

      2. Then apply our Damp Plaster paint (PSB600) which also allows moisture to escape if there is still any present.

      3. Moisture readings should be taken before and after the paint has been stripped off. Allow the substrate to dry for at least 12-14% measured on a Max Doser BD2 setting.

      4. You could also then add our Anti Fungicide Additive (REF502) to the PSB600 to prevent any mould growth.

      • Thank you Plascon for the information that you sent, and I now have a job ahead of me. Thank you again. Hope I get it right! Denise

  24. Hi there, I am currently renting an outbuilding. Due to non stop rains this weekend, I noticed patches of wet areas and could feel and see the water on the same walls. I have 2 young kids as well living here. I have addressed the landlord and they said they will call a builder. What advice can I give them on what products to get to sort this problem?

    • Hi Jason, please kindly note that before we can properly advise you we need to know what type of surface it is that you are wanting to paint (wood, concrete etc.) and what the surface was previously painted with. The more information you can provide the better!

  25. Hi, I have extended my RDP house last year and plastered it inside only and applied the first coat of paint. Now my problem is whenever it rains all the new walls get wet, even my bedroom floor. My question is can I use Plascon Brickseal for outside walls for now? I still want to plaster it at a later stage and use Dampseal for the inside walls.

  26. Hi there. I have a very old garage with 2 walls backed with about 2 metres of soil and rubble. Unfortunately these walls were not properly protected against water. These walls flake and bubble immediately after a new paint job. I cannot dig up the backs of these walls on the outside as they are now my neighbours driveway. Can you kindly advise / assist?

  27. Hi, my wife and I have taken on a project to help a blind couple who live in a RDP house in Athlone Cape Town. The problem is that the house is very damp and the walls are going black. The bedding feels wet and it seems to be rising damp. Please could you advise the best and most cost effective way to proceed?

  28. Hi there. We have a double story home. It seems that moss on the outside is causing (I think it may be ‘eating’ away at the cement) damp on the inside, at the top of the wall and on the outside veranda on the pillars and ceiling. Will Dampseal help with this?

    • Hi Lindi, thank you for querying. Please note that you can use Dampseal, but you must first remove all of the moss and paint as Dampseal can only be applied on a plastered cement substrate.

  29. Hi! Could the following problem be cured with Dampseal?

    I have a North-facing exterior wall to my lounge that suffers from rising damp on the inside and outside. Both in and out the plaster was replaced with waterproof plaster to 950mm height outside and 1000 mm height inside, with a section inside only 500mm high. The replacement water-proof plaster and paint-work over it (in and out) is in good condition. But instruments indicate high moisture content in the replacement and in the new plaster in and outside.

    Outside, the old plaster above the new (up to 1.4m) is flaking off. Also the old plaster, along the join with the new, is lifting off. Inside, the old plaster is similarly lifting along the join with the replacement plaster. Three damp proof contractors diagnose rising damp. Two of them want to replace all the plaster from the ground up to 1.5m, and also drill and inject a chemical damp proof course, both inside and outside. The 3rd contractor recommends only treating the outside wall.

    Can this problem be cured with Dampseal? If not, and the existing old and waterproof plaster must be removed and a new damp proof course created, is it sufficient to only treat the outside, or must the inside be treated also?

  30. Hi, after applying the 3 layers of your DampSeal, can the walls be skimmed and then painted? Also, I’ve overestimated and now have 2 liters of Dampseal already mixed with turpentine left over. How long will this mixture last or should I just dispose of it now?

    • Hi Michelle, thank you for connecting.

      Please note that you cannot (or should not) skim the walls with Rhinolite skimming products. You will need to use a cement plaster like the Polycell Finishing plaster. Once the Dampseal has been mixed with turpentine, it needs to be used within 2 days.

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