How to remove mould and restore rendered porch concrete?

[terrywang]

Probably no sealant / coating was applied when previous owner did the cosmetic change.

As shown, this part is not covered by roof or pergola, exposed to rain and UV directly so mould and corrosion start to show its sign.

Question:

What is the most cost effective way to remove the mould and restore the surface (re-apply part of the surface?), if sealant / protective coating is to be applied, any recommended product for this which can be easily done by DIY noobs?

Thanks in advance.

[EricL]

Hi @terrywang

I suggest using Concrobium 946ml Mould Cleaner. Before using the product, I suggest testing a small area first to make sure that it does not harm or discolour the finish of your concrete porch. You can also use a Ryobi 2000W 2200PSI Pressure Washer to give it a deep clean.  To seal the surface, I recommend using Crommelin 10L Satin DiamondCoat Paving And Concrete Sealer. Please note that this product comes in different finishes so please choose carefully. 

This is a simple clean and seal project. I'm sure you can do this! Make sure to follow the instructions at the back of the can when testing the sealer. Any updates you can provide while carrying out your project would be much appreciated. If you have any other questions, please don't hesitate to post them. Our members would be more than happy to provide advice and information.

If you need further assistance, please let us know.

Eric

[terrywang]

Thanks Eric,

Very helpful. I'll go grab the mould cleaner and Concrete Sealer early Saturday morning and if weather allows I'll start cleaning using pressure washer to get started.

[terrywang]

@EricL Any suggestion for a waterproofing / water repellent sealant (only for a small area which is not covered by either roof or pergola, water accumulates and can sometimes flow to gaps that can penetrates to the garage wall underneath, it's a problem that I am trying to solve along with the mould removing + protection coat (sealant).

[MitchellMc]

Could we perhaps see an image of the area where the water accumulates and sometimes flows underneath the garage wall @terrywang? Is it a crack where the wall and floor join? @EricL and I can suggest a variety of products, but we'd really need to know more details, including where the section that needs sealing is located and the substrates the sealer will be going over.

Keen to assist further.

Mitchell

[terrywang]

Hi Mitchell,

Apologies for the delay in getting back. Busy with work during the week, now it's time to pick up where I left off again lol

Weather's been awful, this gives the task more priority over others.

I've grabbed photos with notes on it

1. uncovered porch, needs some sort of water repellent sealant to extract water efficiently when it rains hard

Uncovered porch - water repellent sealant required

2. Water can go under / penetrate from above - the uncovered porch bits

Water can penetrate thru the gap (slab & brick wall)

3. the porous concrete slab is right above the smaller garage, the front portion of the garage, water had penetrated via the gaps (slab with brick wall - it's been sealed with selley's storm water silicone or similar)

So I consider putting a layer of good waterproof / repellent coating may help to avoid the issue.

porous concrete right under uncovered porch bits

4. When doing it, I'd apply the same coating to the stair (not covered by roof) that connects to the exterior wall of the same garage to avoid water into the wall / garage.

uncovered stairstair view 2

Keen to see your recommendations and ideal products for the purposes.

Happy weekend (it's wet tho...).

Thanks,

Terry

[EricL]

Hello @terrywang

Before you apply a sealer, I suggest investigating all possible sources of leaks going to the garage. It would be a shame to seal this uncovered porch area only to discover that a small crack has been left unsealed. I suggest using Selleys 300g Clear Roof And Gutter Silicone Waterproof Sealant to plug up any cracks or holes that may allow water to flow down your garage wall. 

Once everything has been plugged up, I recommend using Crommelin 4L Natural DiamondCoat Paving And Concrete Sealer. I suggest following the test procedure recommended at the back of the can before applying the sealant. 

Please keep us updated with your progress, we look forward to seeing your porch sealed and your garage wall dry.

If you need further assistance, please let us know.

Eric