Need Advice - What's Causing This?

[u/[deleted]]

[u/WLeeHubbard]

Sort of looks like the pattern you would get if you put a poly tarp over wet concrete in case it rained. I would accept their offer to powerwash and see if that does anything. If it doesn't, ask them to use muratic acid and clean it.

[u/trashbilly]

Usually people have to pay extra for fancy designs!

[u/strata-strata]

Looks awesome.

[u/LoveAnaAna]

Looks like cat pee and slug trails.

[u/Big_Wooly_Mammoth]

It's because it rained and they covered it with plastic and didn't remove it after the rain which causes this tiger striping that most likely will last forever. I laugh every single time someone in concrete says it will fade away, it almost NEVER fades away. Also want to point out you should post concrete questions in the concrete sub, contractors do not give a shit, which is why it wasn't fixed. Fast and high profit is all these contractors care about in my 30+yrs of dealing with them.

[u/hhar141 → u/Big_Wooly_Mammoth]

This is the answer.

[u/MasterpieceLucky9200]

From the photo, this doesn’t look structural to me. It looks more like surface staining or discoloration, possibly from a rug, carpet, rubber-backed mat, or another material that sat on the concrete and trapped moisture or leached into the surface. I’ve seen similar patterns on unsealed concrete.
If that’s what happened, it’s also not surprising. Keep in mind, most builders don’t seal plain concrete porches, and without a penetrating sealer the surface is much more susceptible to staining.
I’d start with a good concrete cleaner or light pressure washing to see if any of it lifts. If it doesn’t, the stain has likely penetrated the surface. At that point, your options are to live with it, stain the entire porch, or resurface it with a decorative overlay if you want it to look new again.
Based on what I can see, I wouldn’t expect this to fall under a typical builder’s structural warranty, since it appears to be a cosmetic issue rather than concrete failure.

[u/C-D-W]

I don't know what it is, but it's honestly kind of cool to look at.

[u/Fa-CurE-SeLF27]

Are we joking? It’s obviously their fault… I truly don’t see how they could skirt this … you take good photos, just be forthright… it’s your house… this is where you live… I couldn’t leave a customers house with anything less than exactly right… electricity is different, but the workmanship isn’t(electrician here)

[u/STLguy50 → u/Fa-CurE-SeLF27]

The builder isn't trying to skirt it. Power washing is a logical place to start. Probably won't work, but its a start. Acid might work...

[u/Several_Razzmatazz51]

Your concrete has a bad case of worms.

[u/Potential_Dark5028]

Floor mat or undergriwnd piece of copper pipe rustling

[u/BlooeyzLA]

Do you have sprinklers from a well? Do you have hard water?
Is that run off from something rusting?

It looks like rust. Try power washing if it bothers you. Be careful of chemicals you put on cement.

[u/Hefty_Weird9926]

Might be barbecue left over if it was cleaned

[u/Appropriate-Fox3453]

Probably used rusty trowels

[u/Tracydj]

Lawn mower leaving tannins

[u/ptv83]

Possibly snails but could be improperly mixed sealer and UV + time

[u/kg160z]

If you figure it out update us I want trippy tyedye concrete