Removing mortar

[Stan in Oly, WA]

My front porch is concrete covered with 1' X 2' pieces of slate. The slate is set in a 1/2" thick bed of mortar. I removed the slate and most of the mortar from the first step down using a cold chisel and a hand sledge. The sheet of mortar came off easily where it had formed a poor bond with the underlying concrete, but chiseling it off is slow going where the bond is good.

I have a Harbor Freight SDS rotary hammer which has been an amazingly tough and useful tool. I have used it for drilling holes in concrete and for breaking up concrete with the square chisel that came with it. There is a flat chisel available for it but the online description of the chisel uses the words "light duty." I know that several other people on this forum own these rotary hammers. Has anyone used one of the flat chisels to remove mortar? How did it work, and how did it hold up? I've got about 20 sq ft of mortar to remove from the porch proper tomorrow, and it's not going to be much fun w/o a power tool.

Thanks, Stan

 

[Billy NY]

Stan, that should work fine, just use care if the substrate, (slate ???) can fracture, not exactly sure what you are chipping against, reading this hap hazzardly, before heading off to work.

I did a precast plank high rise building years back, and the owner wanted the level coat put on, surface prep included me buying 2 Hitachi rotary hammer drills, which I fitted with wide scaling bits and had 2 laborers removing any mortar and concrete from all floors, worked fine, should do the same for you.

 

[Billy NY]

Forgot to add this, when you do so, use the bit at an angle, more so if you are concerned about any weakness of the substrate, the bit should plow right through the mortar layer.

 

[Anonymous-0]

Seven inch diamond wheel on a high speed grinder will take it off in a hurry but will also make a lot of dust. Cover up and use repertory mask and go for it. I used a H.F. setup like this to remove mortar from between bricks and it works far better than anything else and does it in record time. Don't bother showering until your are all done.

 

[Tim B from MA]

Hello Stan,

I'm with Vern, thought a 4-inch dimond blade on a 4-inch grinder will do just as well as a 7-inch. they can be had for about $16 sometimes half that.

Make parrallel "slots" in the mortar and inch or three appart and chip out the rows with a chisel.

I have the Grizzley version of that HF hammer drill you have. I think it has been a great value for using as a hammer drill. I don't think the chipping function will be as productive as a 3 pound sledge and chisel.

 

[John Harmon]

If you have a good air compressor I would suggest getting a body chisel on air such as auto body shops use ,a 1" wide bit and away you go. It works fast to remove stuff such as your parasite mortar bed. I"m afraid the tool you have will cause a lot of damage to the underlying concrete pad.I have several of these body chisels and I use them all the time for jobs such as you are contemplating.Mine are Campbell-Hausfield products. Oil them often when useing in dusty conditions. I put duct tape around the spring and bit to give me a solid place to grasp the bit to guide it.Leather gloves and face shield are a must also.

 

[Anonymous-0]

I am with the 7" diamond opinion myself if you can RENT one. Mine cost me $180.00 each, and will do it a lot faster than the 4 1/4" unit I have. The 4 1/2" are about $45.00, but it is about half as fast man hr wise for the same job. The cheaper diamond blades are better than nothing, but not real good.

When you use a air chisel, be sure to wear ear protection as well. They have their place.

 

[Stan in Oly, WA]

Thanks everyone. Those were some really good suggestions. You gave me some ideas that I ought to be able to use on future jobs, too. That's a nice bonus.

Stan

 

[Stan in Oly, WA]

Hi John,

I took your suggestion and bought a pneumatic chisel gun. It works very well. The real issue for me was getting my POS compressor running. That's been one of those annoying jobs that you can put off almost forever. Having a specific use for it was what it took to get me to quit telling myself I'd do it next time and just fix it. It will be nice to have that back in service again---inadequate and unreliable though it is.

All the best, Stan