new opening in existing cmu wall

[sme76]

I am investigating the possibilities of designing / detailing a new opening in an existing 12" CMU wall. The wall is load bearing and the dimensions of the new opening would be approx. 8ft. square. My question is does anybody know of good procedures and/or details for accomplishing this work? A colleague suggested providing a steel frames made of channels bolted together through the wall and then cutting the opening. Thoughts?

 

[JAE]

We've done the channel detail before...usually have the contractor install channels (web against the wall and flanges pointing out) - both columns along the jambs of the proposed opening, and header beams over the top and resting on the columns.

We then bolt through the wall, enough to carry the weight of the wall into the channel. These can be either through-bolts (hard to do) or adhesive anchors.

After the channels are in place, the contractor begins cutting the CMU away in small sections just below the header channels; installing a cross cover plate under the headers to tie the two header channels together and carry any loose masonry.

Once they've worked across the opening, then the remaining masonry below can be removed as well.

 

[UcfSE]

You can also use angles with the legs turned into the wall to pick up the cmu load. Same bolts or epoxy anchors as well. These can be temporary while they place a precast lintel or permanent. Channels work better with heavier loads.

 

[Lutfi]

I have used UcfSE's suggestion on many projects and very successfully I might add. I usually use an angle that is 1/4 or 3/8 inch thick so it fits nicely in the mortar joint.

Regards

 

[steve1]

Several years back I had a project that required numerous openings to be placed through an existing structural clay tile wall. After discussing the requirements with the contractor we decided to saw cut the openings in the form of an arch. We cut two verticals, then from the top of the verticals we cut a diagonals at 45 degrees. When the tile was removed we framed in with convention posts and beam. It worked well as the arches were self supporting and the cutting was less damaging then using a hammer.

 

[bjb]

I have used JAE's suggestion for load bearing walls and think it works good. I like the angles for light loads. For heavy loads and long spans (longer than you are talking about) I have designed needle beams to support the existing masonry, with the needle beams supported by temporary shoring towers. This would be overkill for your span, I just mention it because it is an option with long span openings and/or very heavy loads.

 

[UcfSE]

What is a needle beam?

 

[JAE]

I believe it is a steel beam or wood beam that is inserted through the wall (perpendicular to the wall) to support only a portion of the wall. Usually these are placed in sequence, using more than one to create a series of support points along the wall.

 

[bjb]

In my experience they are steel beams inserted perpendicular to a masonry wall that provide vertical support until the permanent system is in. They are spaced relatively close together, say 3 to 4 feet apart, and I design them to be very stiff to make sure beam deflection does not crack the wall. I have only used them for temporary support, but for a church modification that I worked on I saw that a previous renovation used needle beams to permanently support a load bearing masonry wall that had a large opening cut into it.