I understand the fundementals but have never done this myself so I need help.
I am pricing a job where I have to cut two openings in a 10″ concrete block wall.
1. What is the best tool to cut through the wall. Can i use my Milwawkie circ saw with a masonry blade? Should I use my Makita grinder? Do I need to rent a particular type of saw?
2. Once I make my perimeter cuts, do I just go nuts with a sledge hammer?
3. To align the perimeter cuts on the inside and outside of the wall I am planning to drill a hole in the center and measuring from there. Got any other method(s)?
4. The Arch is pretty particular of where the windows go so do I need to be at all concerned where they fall in the block pattern? I don’t think so but I want to be thorough.
5. I know that I will need to install a lintel above each window rough opening. What is the best way to cut a channel in the side block to slide the lintel in? Do I need to use non-shrink grout as the bed for the lintel? Or will regular mortar do?
6. Is the lintel one flat peice of 1/4″ steel or is it two 4″L’s? If it’s the L’s the how do I cut the vertical channel in the block? Maybe it’s just a hack job that I then fill with mortar.
6. What is the proper material to use to parge the cut at the exterior wall?
7. Got any idea of what to charge for this? How much time will it take?
Any suggestions are appreciated.
Replies
Sub it out to someone who has the proper equipment to do the job. Trust me, you'll be way ahead of the game in both time and money.
OK. We have a recommendation to sub it out. Point taken and dually noted. However, I still don't know if whoever I hire is doing the job properly. Once I understand the process of demolition/ construction I can make an informed decision on who does it and will be better able to appreciate the cost.
A 10" thick wall is going to be tough with skillsaws. You should be able to do it if the wall isn't solid grouted.
Here's my experience. My new garage overlapped an existing block wall by 4 feet at the property line. I had to cut the wall to end where the new garage would start. This was was an 8" splitface block, solid grouted, 6' high. I used a dry cut diamond blade in my skillsaw 77 and took two passes per side and was still left with about 1 1/2" to 2" uncut. Then I took a Bosch demo hammer and chiseled away at the saw kerf from one side and after about two hard hours of dust sweat and pain, I had a clean cut. Then I had to rent a 60 lb. jack hammer to remove the waste.
I'd never do it like that again. If you don't want to sub it out, then by all means rent yourself one of those gas powered cut-off saws. You should be able to go through if you cut from both sides.
Good luck!
lots of work involved, especially with out good equipment. best to sub to professional mason cutter( cut and remove!). you should layout the cuts yourself--it's nice to grout the cores at the cuts beforehand--easier than forming & grouting after. arch/engineer should spec. lintel size. if you have a lot of block above, roof loads,floor loads....,shoring may be necessary, talk to engineer.
While surfing through the TV channels recently I came upon a rerun of a This Old House episode where, coincidentally, the main task being undertaken was cutting through a poured cement foundation wall to make room for an addition.
The sub actually doing the work had quite a set-up. I remember vertical rails bolted to the foundation wall to guide the saw. The saw itself was air driven and water cooled. He had to use two blades to fully cut through - I think the bigger of the two had a 30" diameter!
Blades were diamond studded which, I think, he said cost $90 an inch to buy. That was a few years ago so I don't know what it might cost today.
IMO, you're probably not going to be able to rent something that complex and than expensive.
The first suggestion on your topic was right. Sub it out.
Griff.
P.S. Was concrete poured into the voids inside the blocks?
Sub it out? It's not the finish surface is it?
I'd lay it out allowing room for the finish materials, scribe with the Milwawkee (at least deep enough for the angles), epoxy in the ends of the 2 angles (the vertical is on the outside), then cut with the previously mentioned gas cutoff and bang it out with a 40 lb demo hammer. Prepare for clouds and clouds of dust. Maybe a buddy could spray water on it as you go. You'll get a ridge between the two cuts - come back a second time with the cutoff and tilt the blade at an angle to undercut the center. Nibble out the corners with the hammer. If it's block like you mentioned, it's not a big deal. Time wise? If you have the tools on site, 4 hours or so, depending on the motivation behind those involved.
Unless the cut wall is going to be the finished surface, then sub it out.
I think there's a few more things to think about before one tackles this on their own.
1. Is the block wall filled?
2. Is their re-bar in the wall.
3. Will I use several 7 1/4" masonry blades or cough up 150.00 for a MK diamond block blade
4. If I go the diamond blade route can I rent a 10" saw or will I have to buy one.
5. What if I run into re-bar, will I try to cut it out with a sawzall or use a cutting torch.
6. If I can't drill a perfectly straight and level centering hole my back side cut is going to be off. Will I crack a block ?
7. If my cut doesn't go all the way through and the cut is close to the edge of another block will it break at the joint or will it break at the cut ?
8. How accurate will I be swinging a 8lb sledge for 2 hours. What happens if I miss and damage the block that I want to save.
9. Could I be doing something else to make money while the sub cuts these holes for me.
10. Is today my lucky day ?
I think the best bet is to at least get an estimate from a concrete/masonry cutting company. That will give you a better perspective of the amount of effort and skill required to do this job correctly.
The first time I tried it I was succesful but I wasted a ton of time and money getting it done. The next time I sub'd it out and found myself ahead of the game all the way around. At the end of that day I realized that I hadn't touched my daily ration of profanity.
Others have mentioned most of the stuff to watch for, rebar, shoring, etc. I have done this type of work many times by myself. Shore whatever framing that is attached to or bares on the wall. Layout the outside cut and make you intial cut and demo outside the wall. Use a demo hammer to break out a few of the block inside the cut line on each side. Use a 1/4" bit to mark your cut locations for the inside cuts. If you have help, have them use a pump up garden sprayer to mist the cut as you make the inside cut. I also drape plastic around the area to contain the dust.
The lintel should be installed by removing blocks above the opening and istalling lintel block or steel. If you need a treated lumber frame to set the window, be sure to allow for it in your layout.
How is your back?
Beyond the detailed descriptions above that all that stuff is heavy. I used a jackhammer in Highschool while working for a landscaper and spent lots of time on the dumb end shaking the bejeebers out of my self and hurting my back in the process. Nothing perminent but still brings out hatred for the guy who invented that torture machine.
Besides the tough work, the output of your labor is generally too heavy to lift.
Good luck. sounds like you are doing it anyway.