How JustAnswer Works:
  • Ask an Expert
    Experts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional Answer
    Via email, text message, or notification as you wait on our site.
    Ask follow up questions if you need to.
  • 100% Satisfaction Guarantee
    Rate the answer you receive.
Ask Dovetail Greene Your Own Question
Dovetail Greene
Dovetail Greene, General Contractor
Category: Home Improvement
Satisfied Customers: 377
Experience:  Licensed Building Contractor & Certified Building Designer
Type Your Home Improvement Question Here...
Dovetail Greene is online now
A new question is answered every 9 seconds

I have a slate walkway on a sand base. The mortar has cracked

This answer was rated:

I have a slate walkway on a sand base. The mortar has cracked and the pieces of slate are loose. I was wanting a concrete slab poured first and then the pieces of slate mortared on the concrete but I was told this couldn't be done because the thickness of the slate varies a little bit. What do you think about a gravel base? Would that give the slate enough stability so the mortar wouldn't break apart again? Thanks for any help.


My name's Kel.


Slate can be laid on a concrete slab.

It's a two step process.

First pour and finish the slab then use a shallow bed of mortar to lay the slate. The shallow bed allows to adjust for varying thickness.


You can also use gravel.

Then use something like sand or granite dust to set the slate. The sand or dust allows you to adjust the height of the slate so the walking surface is truer.


The key to either approach is making sure the area under the patio is well drained.

Make sure no water can get under that. A freeze-thaw cycle will flex the mortar joints can cause them to crack.


Use a vinyl additive with the mortar. That will allow it to flex a bit without cracking.


Does this make sense?

Have I answered your question?

Customer: replied 3 years ago.

This is a front walkway. It is on a gently sloping yard so I guess it drains fairly well. So is it better to put the slate on a concrete base or a gravel base?

The slate will last longer -- be less prone to cracking -- and the joints will last longer if it's on concrete. Many people use gravel because it's less expensive and within the skill set of do-it-yourselfer.
Dovetail Greene and other Home Improvement Specialists are ready to help you
Hello again Carrie. This's Kel. Checking in to see how the slate project's going. . .
Customer: replied 3 years ago.

I'm just trying to find someone to do the slate walkway. I'm in the process of getting bids. Two different people wanted to just put a gravel base down but I told them that I wanted a concrete base Thanks for checking back with me.
Carrie xxxxxx

Hang in there.

Someone'll do it right for ya.



Related Home Improvement Questions