Help Repairing / Redoing Slate Patio and Walkway

[jeffesonm]

I recently purchased my first home, a 1957 ranch that was lovingly cared for by one set of owners until they passed a few years back and I bought it. I am slowly fixing things that need fixing and will eventually start upgrading/renovating the original bathrooms, kitchen, etc.

One of my first projects was rebuilding the small stone wall that goes around the front patio you'll see in these pics. Now I'd like to fix the patio itself, along with the slate walkway that leads from the driveway to the patio. The slates are all in good shape, few nicked corners here and there, but the main problem is they have separated from the concrete underneath and most of the mortar between them has worn away. Here is the overall setup:






Close up of the patio slates:




Exposed edges of the patio... looks like maybe a block wall around the perimeter, concrete slab on top and then another layer of mortar they were originally set in?







Under the slates:





And finally a close up of the walkway. The end near the patio seems to bet set on a thin bed of concrete/mortar, but not so much near the driveway end.




The portion of the patio that abuts the house is protected from the elements by the roof overhang and is largely intact.







The material looks to be in good shape so I'd just assume re-use it, and I have enough driveway room I could relocate all the slates while I prep the concrete underneath. I really don't want to tear up the slab if I don't have to.

Not sure what kind of base is needed for the walkway... the are thin so setting them in sand seems wrong. In NJ so frost is an issue.

Any recommendations for how to go about fixing this?

 

[sportbikerider78]

It is pretty obvious what you need to do first on the patio with a slab. Take up the slate tiles and see what you have got. If you can, I'd just scrap it down and pressure wash, then lay them down in leveling sand and fill between the slate to make an nice fit. I don't see the point in trying to fix them to concrete in any way, because frost will just break them up.

The walkway will likely require you to dig down and either pour concrete or gravel/stone dust. Personally, I love the colored cement walkways that are made from forms to look like pavers but are concrete sections .

 

[gzecc]

If your foundation is good, not totally broken, you could pour a new 4" slab on top of the existing foundation. You'd have to remove all the loose stone and frame around the perimeter. Its a lot of work.

 

[greg13]

If you are going to reuse the stones, put them is a sand bed rather than concrete. Concrete will break up over time due to frost heave unless you go like 4-6" thick with rebar & mesh, Way too much money for a patio or walk way.

 

[jeffesonm]

I will pull up a section of the slates and see how it looks below.

 

[JA600L]

An easy patch job would be to add polymeric sand and set them with that. I'm not sure how well that would work with slate. Just a thought.

 

[jeffesonm]

I pulled up a little section of the slates... it looks like they were leveled in a shallow bed of sand and then mortar or something filled in the spaces:



The concrete slab itself seems to be fine, at least the section I' pulled up here. Maybe I could I power wash out all the joints, re-level any misplaced slates and then re-fill them with mortar or polymeric sand?

 

[sportbikerider78]

Take a look after you clean it up. You can always grind down any high spots and patch any missing material. Maybe do a sealer on top of it?

 

[JA600L]

Get some sand and level them by hand adding a bit as needed. Once everything is in place and leveled, brush polymeric sand all over it and hose to set. The nice thing about polymeric sand is you can always easily add more.

 

[jeffesonm]

Here's what it looks like when you clean off all the sand and eroded concrete gunk:

 

[joes169]

I'm a concrete & masonry contractor, and I've layed thousands of sq. feet of similar stone on concrete, here's my professional opinion:

If you want to repair the sidewalk and patio every 2-3 years, bed the stone in sand and use polymeric sand in the joints. If you want it to last for decades w/o repair, wet-set the stone in morter and grout the joints.

Obviously, the latter requires more work & detail to conquer, but it's a far superior installation IMPO. If the conrete is in good shape and has been that way for 50-60 years, there's no reason to re-invent the wheel.

You'll want to remove all of the stone, clean them & the slab well, and take a close look at the condition of the slab. When we do these, we often take a few photos, print them off, and label the stone & photos to ensure we can lay it out the same exact way. If you have access to more matching material, this isn't as important. You'll want to fully bed the stone in a mortar bed (we generally use mostly Portalnd cement & sand with just enough lime to minimize water bleed-out and some bonding admixture) and back-butter all of the stone with a high quality modified thinset that's suitable for exterior use. Laticrete makes good thinset's for this. Every once in a while, pull a stone after setting to ensure 100% bed coverage, or in other words, no voids. Lastly, we grout all of the joints with a mostly Portalnd/sand mixture, tolled with a concave jointer.

 

[semipro]

I'd be concerned about frost heave whether bedded in sand or mortar. The problem is the concrete slab that prevents water from draining through.
If it were my place I'd consider placing a wood deck above the concrete and using the stone elsewhere.
There are also interlocking wood deck tiles that can be placed on top of concrete.

 

[jeffesonm]

I'm a concrete & masonry contractor, and I've layed thousands of sq. feet of similar stone on concrete, here's my professional opinion:

If you want to repair the sidewalk and patio every 2-3 years, bed the stone in sand and use polymeric sand in the joints. If you want it to last for decades w/o repair, wet-set the stone in morter and grout the joints.

Obviously, the latter requires more work & detail to conquer, but it's a far superior installation IMPO. If the conrete is in good shape and has been that way for 50-60 years, there's no reason to re-invent the wheel.

You'll want to remove all of the stone, clean them & the slab well, and take a close look at the condition of the slab. When we do these, we often take a few photos, print them off, and label the stone & photos to ensure we can lay it out the same exact way. If you have access to more matching material, this isn't as important. You'll want to fully bed the stone in a mortar bed (we generally use mostly Portalnd cement & sand with just enough lime to minimize water bleed-out and some bonding admixture) and back-butter all of the stone with a high quality modified thinset that's suitable for exterior use. Laticrete makes good thinset's for this. Every once in a while, pull a stone after setting to ensure 100% bed coverage, or in other words, no voids. Lastly, we grout all of the joints with a mostly Portalnd/sand mixture, tolled with a concave jointer.

Thank you, appreciate the pro advice I am 100% going to take the time to do it right.

I will remove all of the stone next and clean it and the slab.... I have enough room in the driveway to lay it out as-is, so might do that, or stack it up in rows or something.

Few questions, I'm sure I'll have more later.

1) Is powerwashing the slab good enough? Or clean it up with muriatic acid?

2) Some of the spalling is maybe 1/2" - 3/4" deep... do I need a skim coat of concrete to get things close to flat first?

3) When you say fully bed the stone in mortar, do you mean like lay a thin layer of of mortar on the concrete, then back-butter stone with thinset and set the tiles?

 

[joes169]

Thank you, appreciate the pro advice I am 100% going to take the time to do it right.

I will remove all of the stone next and clean it and the slab.... I have enough room in the driveway to lay it out as-is, so might do that, or stack it up in rows or something.

Few questions, I'm sure I'll have more later.

1) Is powerwashing the slab good enough? Or clean it up with muriatic acid?

Yes, it should get it plenty clean.

2) Some of the spalling is maybe 1/2" - 3/4" deep... do I need a skim coat of concrete to get things close to flat first?

With the Portland cement, that depth shouldn't be a problem at all, and won't need a pre-fill. How much room would you estimate you have between the stone and the concrete to work with? Anything less than 1/2" is a pain in my experiences. On the other hand, we set plenty of irregular flagstone through the years that require 2"+ bedding mud, and they perform fine.

3) When you say fully bed the stone in mortar, do you mean like lay a thin layer of of mortar on the concrete, then back-butter stone with thinset and set the tiles?

Yes. By fully bedded, I'm referring to a lack of voids in the mud bed.

Best of luck.

 

[sportbikerider78]

I didn't know you could tile an open slab in a climate that sees very cold temps. Interesting.

I always thought the grout would absorb moisture from above and below and crack to high heaven when it freezes.

 

[jeffesonm]

All the slate has been removed. There are some pretty good sized cracks in the slab, and one area in particular where one side lifted (or the other side settled)










Am I looking at a new slab here? I would hate to tile this all back together just to have the slab move again and break it apart.

 

[gzecc]

Could you pour a new slab 4" directly on top? Do the elevations work?

 

[semipro]

That slab looks unstable and I'd bet stone set on top of it would crack, move, break.
Its hard to believe it even has steel reinforcement in it given those slab tectonics.

 

[jeffesonm]

I doubt there's any steel in there. Believe it or not, I have some pics of its construction in 1957 and it looks like it was just poured on top of a pile of dirt, so no surprise it's settled.

 

[gzecc]

Its settled now. Just need to decide wet or dry new cement on top.