[klaaar]

There is a walkway including steps from the public sidewalk to the front door that I am about to work on. There's ten steps or so, in small groups, separated by runs of flat walkway. The steps (and small patio at front door) are mostly tight and strong, but the runs are falling apart. They were apparently built years ago by laying the rectangular, multi-size flags on very coarse sand, and then filling joints with mortar. We plan to remove sand and loose mortar and dispose off site.

We have built a good number of mortared patios and walkways, but haven't done a job quite like this before. We believe there is a good although uneven poured base including chunks of stone, so we plan to relay the clean flags on mortar on the base.

1. where the existing mortar on patio and steps is strong but with cracks, should we try to fill cracks with a specialized, tinted caulk? I assume this would be most economical unless the crack was too wide.

2. where the existing base shows cracks (we assume it might), should we fill with same type of caulk/sealant then spread mortar on top 1 day later?

3. after we power wash the existing tight mortar, we assume the color would not match new, undyed mortar. Do you guys normally put a touch of color in mortar to try to mimic the look of weathered mortar in the hardscape?

Any insights, suggestions, criticisms are appreciated.

[Stonehenge]

If there are cracks in the concrete this work is going over, that concrete needs to be replaced. Sealing it won't prevent it from freeze-thaw movement.

Next, as Agla has suggested on several occasions, when you're mortaring these stone atop concrete, you need to provide for relief/expansion joints in both the concrete and the stone above it.

Hope that helps.

[klaaar]

That does help, thank you. I read over the other related threads and that, too, was helpful.


Today we learned that the concrete base under the walkway is 6" thick and was poured over a crushed type of stone (black and very porous and light). Most of the flagstones we removed today were dry-laid on 1 to 4" of course sand, but some were on top of 1 to 2" of mortar on top of 1 to 2" of course sand (sand composed of particles up to 1/3rd inch). Still others (a minority) are properly mortared to the base. It is an amazing sight to behold.

In essence now we have a strong base that is about 50% flat and 50% with an "undulating" surface due to the strange construction techniques. The undulations are composed of what I assume was used as mortar - it is strong as stone but there is no large gravel in it. Basically our mortar layer under the flags will be 1 to 4" thick when we lay over the existing base. What do think of cutting grooves with a chop saw every inch or so to increase the holding power of the new mortar?

[PSUscaper]

If the existing concrete is cracked what is making you think this is a stable base for more concrete work on top of it????

For the amout of trouble you seem to be going through with this already screwed up base, you could of already ripped it out and poured a new one.

Explain to the customer that installing new work on top of the old will only lead to the same problems down the road. The money they spend now will save them money later.

Also, from the sounds of it, the time you are spending trying to work with this mess is going to have to get passed on to client, at least I hope. How much trouble is it going to be to work with this? Are you billing out by the hour? Are you going to warranty this work???

Think about this. You can't believe the mess that is already there......imagine what the next contractor says when they come along and see the bigger mess that you built on top of it.

Sometimes its hard to do the right thing, but it has to be done.

[klaaar]

The existing base is not cracked, just topped with a bunch of crap.

Considering the inaccessibility to this area, replacing the base is not an option dealing with our budget. I don't think I would replace it anyway if access was easy. Once we remove all the toppings, we have quite the solid base, if not flat. New mortar would have to be 1 to 4" thick. Should that in itself be a concern?

(PSU - thanks for your frank guidance)