We had a Allen Block retaining wall built a couple years ago, but one thing that bothers me is the landscaper didn’t butt the end of the wall tight where it meets the concrete pillar support for our deck. The problem is because there’s this gap, it has caused some of the backfill gravel and dirt to spill out at the end. This has also caused the ground above this segment to dip because the dirt has been able to wash out. So my brilliant idea was to use some Great Stuff Big Gap foam to seal the void. I didn’t really want anything too permanent in case I screwed it up, so that way I could cut it out if I needed to. Well needless to say my efforts look like crap, and I’m not really sure this stuff will stand up to being exposed to rain and such. My wife’s biggest problem with it is that the color is yellowish. I thought it was going to be more grayish from the can pic, but it really doesn’t match the color of the wall. What should I do about this situation?

 

That expanding foam is hard to remove, I'd be inclined to scrape off the excess and paint it a light grey.

 

You could mortar over it with a product like Quikrete Stucco base mix, and it will look better, but it won't last many years because of movement and freeze/thaw cycles. Brush a slurry of the mix onto the concrete surfaces before stuccoing. (Helps with bonding) Using a piece of landscaping block facing to imprint some texture into it might make it look better than just a smooth patch.

 

I wish they had some type of concrete in a squirt tube or something.

If I painted it, any particular kind of paint I need that will withstand the rain and protect the foam?

I see Great Stuff does make a gray colored Pest Block foam...but once again I’m not sure this stuff is designed to be exposed to rain.

Grrrr I wish I could go back in time and have the landscaper make a proper seal against the pillar!

 

Is it Quikrete pre-mixed Stucco Patch you are talking about? I see they have a quart size of the stuff at Home Depot. Would I just put that on top and smooth it out with a putty knife? How big of a gap can that stuff fill?

I also see a pre-mixed small tub of Quickrete quick setting concrete mix. I’m just afraid if I screw something up, I’m not going to be able to remove it. I don’t want to damage my wall blocks with whatever I do.

 

Most any exterior latex paint should do fine.

 

No! Its the dry cement bag sold at home depot. https://www.quikrete.com/productline...asecoatpro.asp

I would probably fill it in 2 or 3 applications that are not more than 1" thick. Leaving a scratched surface and brush slurry each time so that the next coat can lock into the last one. You will find that several coats will bond better than one thick one. The weight of a thick coat may cause it to pull away under its own weight.

Leaving the foam there is fine. I would stucco right over it.

 

Should have dug out the bed, laid landscape fabric on the inside an been done!