Blue Stone over covered concrete porch-2 years old

by Rod

What mortar should I use to do a fat bed- S or N or portland - sand mix? I want to adjust for various thicknesses of the dimensional blue stone. Should I wash the back of each stone before laying it? What acid wash should I use for the concrete porch before laying stone? Should I put an additive in entire mud batch or just in the mud to butter the backs and the concrete porch prior to setting each stone.

Thanks for any help.

Comments for Blue Stone over covered concrete porch-2 years old

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great advice
by: David

Dear Jayson,

Thanks for the info. My dad will be excited to see your tips and it will help a lot of people who come to this site.

Take care,


Stone porch
by: Jayson

First - Mortar does not go in the ground, it is for walls. It is not water proof and degrades fast under ground it also promote a bad stone bond, lifting, crumbling, and popping. It is a compression agent, not a bonding agent.

If anyone ever shoved up to your house to look at a stone porch bid and says mortar, politley ask them to leave.

You are looking for someone who speacializes in laying stone, not a landscaper or bricklayer but someone in between. It takes a speacial skill set for proper stone porch install. Stone masons are a good start.

I use a old school mix that a old stone mason taught me. 1 part play sand, 1 part slag sand, and 1 part Portland with 10% hydrated (finish lime) added to the portland. This mix has a glue like effect for stone.

Mix is as waterproof as it gets. This mix will not shrink. Stone will not pop or shift. I've seen porches that are 60+ years old layed in this that look perfect still.

Steps I use:

4" or 6" concrete base depending on size. 1" of custom portland mix to lay stone in. Then the stone are grouted (joints filled) in the same mix.

Strips of 1/2" wood used for spacers will help keep tight, even joints as you go.

You will lay the stone then rake out the portland from the joints, I use a shopvac to pick up the loose stuff as I go. Then a sponge and bucket of water to wash all the stone tops to get any portland smears you have off the tops. After the tops are clean you go back with the same mix you used to lay the stone (add some water to get it loose) and a grout (cake bag) fill all the joints. Then use a sponge and water and go over the joints like cleaning jointed tile.

This will pull all the gray (portland) off of the top of the joints leaving a aged or exposed finish. Finish will be a ash gray with black stones in it from the slag, like a salt and pepper look.

You can wash with acid but chance fading the stone color out a little, (does add a aged look) clean as you go is your best bet. Cultered stone acid works well, does not fade stone.

I did a pair of porches last year at a bigger home. Home owner never seen anything like it before. I'm back now doing another porch and a patio for him. Had a proffesional landscaper show up to excavate the space for the new porch. He thought the 2 porches I did last year were original to the house.

It might cost twice as much as a sand laid porch, and take 3 times the man hours to lay it, but it will last well past your life time and require no maintenence.

by: Anonymous

Use Muriatic Acid to clean your concrete

Owner/D&D Stone Brokers
by: Don

If your stone is popping up it could be due to the thickness of the stone in cold weather and I would use a S type mortar mix, because this will give you more time to set-up your stone and the laticrete should have worked, but you could try a acid based cleaner for the concrete. Is your Blue Stone cut squares or irregular shape.

talk to a local stoneyard
by: David

Dear Rod,

My dad has laid bluestone a few times using Portland Type I-II here in Denver, Colorado and it seemed to go ok.

However, one time he laid bluestone and the stone would pop up every couple of years and it only did it in certain sections of the sidewalk. He used a strong additive called laticrete and the stone would still keep popping up. He talked to his suppliers and nothing seemed to work. (Maybe a weather phenomenon?)

My dad is now reluctant to lay the stone until he can find a definitive answer about why those stones popped up on him.

You need to talk to your supplier and ask him what he recommends. Make sure he has done jobs in your area with your stone so that you know the process went well.

Sorry I couldn't be more specific for you, but I don't want to mislead you into something I'm not totally sure about.

Great luck!


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