its always better to fix a problem rather than hoping its not too bad. Its not really that much more to replace.

Just cut out and replace the damaged section, if possible make sure the area you want to tile covers the whole patch (don't have to repaint anything & the patching doesn't really need to be top coated or super pretty as it will be hidden by the tiles)

Sorry, aweebitkiwi, but Gyprock should not be used near water. Villaboard or a similar waterproof board should be used and then paint should be enough, especially if you use a semi-gloss paint. I don't think you will find it too expensive to have it totally replaced and then you never have to worry about it again.

Thanks suancol - I thought it was mandatory, I know it definitely is in bathrooms, but I wasn't sure if the poster might be in NZ and they have different building codes.

Cut out the whole damaged section and replace it with a sheet of fibre board suitable for laundries and bathrooms. You will need to apply a waterproofing substance first along all the walls that are anywhere near the water source before you tile the walls as you don't want mould to be building up behind the tiles without your knowledge. If you are just going to paint the walls and not apply tiles or any other splashback you will be able to see if there is mould build up and can skip the waterproofing step, but for a lasting job, do the lot. It will cost you less than $100.

Any build which requires Council approval in NSW must have Villaboard linings in wet areas and waterproofing for which Council does an inspection before tiles are fixed and also requires a certificate from the waterproofer. It therefore would be wise to follow the same procedure when doing minor renovations

I’m not sure if this was just a small renovation or a large new build but who is your Building Surveyor??!! They should not have given you occupancy without a splashback and a Waterproofing Certificate. Whomever did the work needs to come back and rectify. Take off the benchtop cut out the damage and replace with correct waterproof board. Then tile or glass spashback with plenty of sealer. Good luck

To me it's a case of fix it and get it right or hope and pray that history doesn't repeat and you have to do it again. It's always more expensive to do it right once but cheaper than doing it wrong a multitude of times. You must without fail remove the plasterboard to allow what's behind it to dry out as well. If its timber, as I suspect, and you seal it up with dampness in the timber you will not only be revisiting it too soon but it will be a much larger and more expensive rectification job because you will be replacing timber framing, relining, rewaterproofing and either tiling or sheeting over the wall once more. If budget is really tight, consider Aquapanel by Laminex.

Any reason they can't use Gyprock Aquacheck which is virtually waterproof rather than Villaboard to patch rather than doing the lot in Villaboard?? Then waterproof over the area to be tiled and tile splash back. Need to check the timber in behind and dry out - agree. Silicone right around basin when finished too to stop water getting in again. DIY project if that works.

First check if house has a builders warranty ie the house has recently been built then clain against builder to rectify at no cost to you.

2. All wet ares should not have drywall installed anywhere near water outlets. water proof cement sheeting to be used only.

3. Suggest all complete wall to be replaced and inspected by licenced builder otherwise same problem will come back a proper job is required not a band aid solution.

when you go to sell later it will pass inspection , so do it right the first time and have peace of mind.

I'd be interested to find out the actual cause of the wet area damage. Is it just from splash and ponding on the benchtop or is there something more sinister happening to place enough water at the scene of the damage such as a leaking clamped connection in the in wall plumbing. Always confirm the cause of the water damage and make sure its overcome.