Decorating after water damage

Leaks and burst pipes are the bane of any householder and even the smallest amount of water damage can take a lot of time and money to rectify.

Here are a few questions on the subject of making good paintwork after a water leak…


After a pipe leaked in an upstairs bathroom and the plaster in the wall downstairs, above the kitchen window, became wet. A metal strip just under the surface of the plaster became corroded (it looks like rusted iron) and this flaked the top layer of plaster off. This is along the edge of the underside of the window (where a concrete lintel might be expected to be, above the window).

The rusty metal is exposed in only two places and these are 2 to 3 inches wide and a quarter inch or so high. The pipework is long fixed and the wall is fully dry. I need to decorate the kitchen.

How should I treat the rusty iron in order to then fill or plaster over it? I guess there is a product that will seal it but I can find no information on how to proceed.

It is quite a small repair but I don’t want the rust to lift or stain through what I put over it and I am guessing that putting wet filler onto it will reactivate the rust.


Hi Andy

The steps I would take in this situation would be:

  • Ensure all traces of damp have been eliminated and the affected area has fully-dried out.
  • Cut back the affected plaster beyond the rusty area and, if possible, remove the rust with a scraper and/or a wire brush and abrasive paper.
  • Prime all the exposed metal with an oil-based metal primer with zinc content. (Zinc-phosphate, ideally, and 2 coats are better the one).
  • Allow to dry for at least 48 hours then repair as normal and redecorate.

Hope this helps although there is always a risk that there has been some damp contamination in areas you can’t see (such as the other side of the metal beam) and this will eventually work its way through to the surface.

However, it is almost impossible to mitigate against this and you will just have to wait and see.

That said, any minor staining that does eventually work through can be treated with a coat of the same metal primer before redecorating.


After a leak, fluffy salts have been coming out of the paint. It’s gypsum plastered. I’m not sure what to do – please can you advise? READ MORE…

I have an Edwardian mid-terrace house which had a water leak under the hallway floor. The leak was fixed six months ago but I don’t know how long it had been going on for.

Dampness has crept up the hallway (party) wall from the site of the leak and fluffy salts have been coming out of the paint. It’s gypsum plastered. I’m not sure what to do – please can you advise? Hannah

The fluffy salts is efflorescence, which is a natural occurrence when moisture is drying out beneath the surface. Assuming the source of the leak is definitely fixed you should just wait until the drying out process has completed before attempting to redecorate.

This could take several months.

I had a leak on en-suite it spread water through the hallway ceiling and had few cracks on coving , I put heaters and humidifier. When it’s completely dry do you fill cracks first or put stain blocker first fill and apply stain blocker again? Which is the best stain blocker I should get for water leak damage? READ MORE…

I would apply the stain blocker first and again when the filling is done. For a water-based stain you should use a solvent-based sealer such as Zinsser B-i-n Primer & Sealer (amazon link). Once this has dried you can use a water based finish over the top.

We have a fifties house which is painted with sandtex. We had a leak in flat roof over kitchen (we have now had a new roof there) but prior to that damp got down inside the house walls in places. I painted bitumen over this area several years ago and eventually water came between the bitumen and the outside paint when damp stopped getting inside.
The paint on top of the bitumen needs to be removed but would you suggest the Zinsser’s Bulls Eye 123 Plus acrylic primer would seal the bitumen ( as you suggested to someone else) or perhaps another product so we can paint that area with Sandtex?

Zinsser’s Bulls Eye 123 will seal the bitumen but, if it’s more cost effective to do so, a standard acrylic primer/undercoat will do the job just as well.

It really depends how big an area you need to cover?

We have had a leak from the water pipe that carries the water into the house. This has resulted in water running around the cavities all around the ground floor of our house. We have had a firm in to use machines to blow hot air into the cavities to dry them out. The paint in all the rooms has bubbled. Will I need to use special paint so that I have no future problems with the paintwork? READ MORE…

The most important thing is that you allow the cavities to dry out properly before even thinking of decoration. This is going to take a very long time but it is essential since any trapped moisture is going to cause no end of problems with interstitial condensation.

Once the walls have dried out you should remove any loose paint and redecorate with a breathable finish such as Dulux Trade Supermatt.

Upstairs had a leak… we have been using a dehumidifier for several weeks to help dry the walls and are now thinking of redecorating. The walls and ceiling have liner paper on them which is very stained, one of the walls is an outside wall. I’ve used oil based paint on smaller stains before but am not sure if painting an entire wall in it is the correct thing to do or whether to repaper. If the latter do we need to take off the old layer first? Your advice would be very welcome. READ MORE…

Yes, take the old layer off – it will be worth it in the long run. Then check there is no damp still coming through.

The likelihood is that your external wall is a single skin (old stone type walls) and penetration of some moisture is perfectly normal. It could also be due to a minor building defect such as loose mortar or a blocked gutter; or a combination of the two.

Depending on how severe the water damage is will determine the correct way forward but if you think it’s only minor and there are no obvious defects then redecorate in the normal manner.

For a severe problem, use a moisture vapour permeable emulsion such as Crown Covermatt (cheap) or Earhtborn clay paint (expensive). In other words, a paint with no oil or vinyl content.

Sorry but I can no longer dedicate the time to lengthy email conversations but feel free to comment here if you need more information.

See Also
Painting over a stained surface
Stain Blockers
Damp wall at window reveal causing staining and blistering of paint covering
Damp Problems