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What is the best way to cut through a concrete block wall?

Question says it all -

Need to cut a concrete block wall for a door. Have looked at rental equipment and co's that do this.

Any experience in favor or DIY or contracting out?

Thanks.
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Old 01-09-2008, 09:02 AM
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If you do this, remember that the blocks above the door will need a steel support. It can be done with rental equipment, but I wouldn't advise it unless you have had some construction experience.
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Old 01-09-2008, 09:07 AM
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Old 01-09-2008, 09:09 AM
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We normally detail that with steel channels epoxied into the remaining concrete block R.O., but there are many ways to do it.

If commercial, you'll likely need a structural engineer's detail for this.

Also keep in mind that you may be encounter rebar and/or bond beams inside the wall. Please make sure these things are checked before cutting.
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Old 01-09-2008, 09:14 AM
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The proper tool is a gas powered hand held concrete saw.

But... hire it out. It's not complicated, but most of the job is having the right tool and wear and tear on the blade. The rental co will charge you for both, so you might as well have a pro come out and do the labor end of it too.

If there is no digging I wouldn't expect the charge to be more than a few hundred dollars. You'll have to dispose of the concrete and do the cleanup, but the cut will be straight and really that's what you are looking for in the long run.

I've done it both ways and whenever I lift a rented gas saw I wonder why the hell I didn't hire someone to do the job.
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Old 01-09-2008, 09:14 AM
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Old 01-09-2008, 09:27 AM
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Old 01-09-2008, 09:28 AM
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Old 01-09-2008, 09:33 AM
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Thanks all. Will start looking for local co's for quotes.

Sounds like while this may be DIY, it is not worth the hassle.
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Old 01-09-2008, 09:42 AM
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In Russia, I hear they use old Jaguars, Cayennes, CGT's, and stuff like that.
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Old 01-09-2008, 10:26 AM
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Quote:
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In Russia, I hear they use old Jaguars, Cayennes, CGT's, and stuff like that.
In Russia, concrete block wall cut you!
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Old 01-09-2008, 10:31 AM
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Try a concrete coring company. They do it all the time and it won't take too long. Talking with an engineer regarding the support above your door would probably be a good idea.

If you were talking about running a dryer duct out through the wall then I'd say rent the hammer drill and bit from Home Depot. I did one hole by drilling small holes in a circle and chipping them out....it took hours. The second hole I rented the tool and it literally took 10 minutes.
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Old 01-09-2008, 11:12 AM
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Project involves cutting a concrete black wall to add a 2nd door from the office into the warehouse. Appropriate framing and a steel fire door would finish it off.
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In Russia, I hear they use old Jaguars, Cayennes, CGT's, and stuff like that.
Maxim can help you with this... well, if you can find him that is!
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Old 01-09-2008, 11:49 AM
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Dean,
Jeff (P-O-P) is right. Beware of rebar and bond beams built into the wall. If your wall has it, then cutting through it is a serious consideration. If on the other hand this is something less critical, something at your home that is non-structural, it CAN be done as a DIY job. I've done it.

I have cut through masonry block walls using an ordinary Skil saw and a carborundum blade. Carborundum will cut through metal too. They make a LOT of dust and you MUST NOT teak or bind them as they can come apart and hurt you...badly I hear! If I did it again I'd suggest a tile blade - if no rebar. They're about $25 last time I bought one at Home Depot. You've got to use running water to cool and lube the blade and you will only cut through deep enough to cut the outer wall of the block most likely. If it is grouted solid then you've got more work in front of you. If you have access to both side of the wall (I hope) you'd cut both sides.

Jeff is also right that if you are thinking of a doorway in this wall, a structural steel frame will have to be installed. There are several ways of doing this, but it is necessary. I'm not encouraging you to do this if you don't know what you're dealing with structurally. Best of luck. Post what you are working with and several of us could probably give you more accurate advise.
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Old 01-09-2008, 11:52 AM
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D.i.y.

Do It Yourself;

Why not do it yourself, it's a messy job and most contractors will be expensive for this kind of work? So if you're not happy with a quote, DIY:

Initial examination of proposed location:
Examine the location where you intend to install the doorway. Is there any chance the wall could be bearing the weight of something out of the ordinary? It's likely a bearing wall of some kind, but a bearing wall carrying evenly distributed loads and not a point load would be the initial requirement for location?

If the wall is bearing; you will need to complete the full procedure stated below;
If the wall is not bearing, then you will only need to install the steel lintel beam and not the concrete grout mixture as stated below;

Take a small chisel and hammer and chip into the block in the proposed location. The block may be filled with an insulation material, so start higher and examine the blocks you intend to remove. Depending on whether you're doing an interior wall or exterior wall? They should be hollow. Check the full width of the proposed doorway. If it's an exterior wall, you will want to excavate the exterior side first. Get a shovel, it doesn't take long.

Tools:
The best tool to use is a concrete cut off saw; looks like a chainsaw with a blade on the end. You can use a skilsaw fitted with a conc cutting blade, but the right tool is much better. Rent this from your local rental co. A good sledge hammer will be required, a square chisel. A wheelbarrow and shovel for mixing concrete slurry. Ask your rental company if they have a tool to inject a concrete slurry mix (grout) into an opening. These look like large caulking guns. If not, you can use a funnel system.

Safety glasses or shield is a must. Gloves and proper clothing.

Materials:
You will need a steel lintel support beam that will be inserted into the block wall above the proposed doorway. See sketch below. You will need a a conrete grout mix for column and bond beam along the perimeter of the proposed opening. Buy the highest strength powder you can find, as you will be mixing the grout very soupy (which takes away from overall strength). Also try to use a non-shrink grout mix, or even expanding?

Prep:

Hoard and Tarp the area for dust containment. Tape off any duct vents, etc. This is a dusty, messy job.

The Job:
Sawcut a large reglet opening that will allow you to fully insert your steel lintel beam just above the proposed door opening. The steel will serve as a lintel support for the new opening as well as a concrete grout 'stop' for the new bond beam that you will place above. Insert the steel fully into place.

Cut small openings at the bottom of each column. Drain/remove any insulation in the column area. Carefully chisel out or drill large holes above the proposed door opening as shown in the sketch below. These holes will be used to inject your concrete grout mix. Use a heavy wire to fish up and down the columns to ensure they are clear and ready to recieve grouting. Feel free to break open small openings to ensure the concrete can flow into the column areas.

Mix your grout mixture very wet so that it will run into the block as desired. You will be creating a concrete column on each side of the doorway that leads to a concrete bond beam above the door. The concrete bond beam assisted by the steel lintel will transfer the weight load from above to the side columns.
Fill the block all the way up to the holes, including filling in the holes.

Use an injection tool or a funnel system to place the grout mixture into the wall. You can make the mixture soupy, but be sure to use a high strength powder. Use plywood forms to keep the grout from running out any holes, but ensure that the grout is everywhere that you want it. Allow the grout to dry for 24 to 48 hours.

Using the concrete saw you can scripe a sawcut in the block where you want to remove for the door opening. Then use your sledge hammer and chisel to remove the unwanted block. Make final adjustments with your hammer and chisel; possibly a grinder?

Remove unwanted debris and enjoy your new doorway!

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Old 01-09-2008, 12:39 PM
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It's not just a question of whether it's bearing, it's a question of whether it's a shear wall. Much harder to tell by having some contractor "just look at it". You need to have a professional (architect or engineer) look at it before you go screwing around.

I had a couple of yahoos with cutting saws do a number on a concrete slab once - turns out the slab was acting as a diaphragm and it ended up costing the G.C. about $30k to fix the f*ckup.

Moral: Check twice, cut once (or not at all).
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Old 01-09-2008, 12:44 PM
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Old 01-09-2008, 01:44 PM
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My tool of choice. Hell, I'd come do it for you, but I can't guarantee the lines would be straight.

I'm with URY, though. I use this in bunker gear with helmet, faceshield and serious gloves.

It's heavy, cumbersome, tiring and dangerous. Fun as all shyt, but all of the foregoing as well.

If you want to play, pay someone to come do the aperture, and before they make the cuts, ask if you can try the saw "inside the lines".

JP
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