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eamesdaedelus
02-01-2007, 09:39 PM
What is the commonly accepted practice for lintels/headers for garage door openings in reinforced CMU walls. I have a 16' garage door opening in a block wall (12" block at this wall) with a parapet above, so only a roof load to add to the dead load of the block itself and the dead load of the lintel/header.

I know this sort of thing is done quite a bit, and I intend to get my engineer to check it, but he works best if i give him a point of departure for how I'd like to have it built.

Any help would be greatly appreciated.

Mark Meyer
designSTUDIOmodern.com

concretemasonry
02-02-2007, 01:31 PM
You should have a professional look at the design of something to span the 16' opening and carry the dead and live loads. That is a substantial span, especially if it happens to be a flat roof. The parapet indicates it may be flat or have other loads.

Much depends on the distance from the top of the opening to the level of the roof bearing. If it is enough, you might be able to do it with a concrete block lintel (not bond beam), but you may need a steel beam that you can face with a 4" block to maintain continuity of appearance.

Dick

eamesdaedelus
02-02-2007, 05:35 PM
I intend to do that, but like I said, my engineer works MUCH quicker if I can take him a starting point on rebar sizing and lintel depth. I stopped by another project I know of today and they are doing a 16' span with the same amount of block wall above and a larger roof load. It is being done with 8" lintel block and a stack bond pattern so I know this can be done with simple reinforced block bond beams and lintel blocks.

MCC
02-03-2007, 01:35 PM
You Need The Final Direction From Your Engineer But I Would Suggest A Concrete Lintel Instead Of Block. Your Opening Will Probably Need A 16" High Lintel With # 7 Or # 8 Re-bar.

concretemasonry
02-03-2007, 02:43 PM
If your engineer wants a lintel, either a block lintel built in place or precast concrete lintel will work. The lintel is designed for a specific load and it can be achieved several ways.

If a precast lintel is available immediately and you have the ability to get it in place without cracking it, use it if you need it immediately. A built in place lintel offers the ability the have continuity of reinforcement, if desired. After being involved with lintels in Minnesota, Pennsylvania, Virginia and Connecticutt, I recognize the problems of delivering and erecting relatively heavy, long, limber concrete lintels.

If that is not available a block lintel with shoring (two or three 4x4s) can be built in place immediately. You can then go about finishing the trusses and roofing. Depending on the opinion of the engineer you should be able to remove the shoring quicker than you can get a special precast lintel made.

Forget about the guy down the street. - It is a different situation and just because it is still standing does not make it right or adequate. Trust the engineer you have hired.

MCC
02-03-2007, 03:27 PM
Just To Clear Up My Last Post I Was Talking About A Cast In Place Concrete Lintel.

eamesdaedelus
02-09-2007, 08:43 AM
Well my engineer is given me preliminary sizing for the lintel over my garage door. He is saying I'll need (6x) #6 bars with stirrups every 8". This is in an 8x16" high lintel. Question is how do I get that much rebar into the fairly small cavity of the lintel block and the bond beam block above and how do we get stirrups to run between the two layers of block?

It seems to me he is going about this as if it is a CIP concrete beam. I know that this can be done with a double height (16") block lintel, as I know of specific examples that have far heavier loading conditions spanning a bit further.

Knowing this to be the spec, how would you concrete block masters go about this?

Thanks,
Mark

concretemasonry
02-09-2007, 09:54 AM
Is this new construction? If so, what do the permit drawings say? If you are remodeling, what was the previous condition? Where do the two layers of block come from? - Are you considering 2- 8" courses of block as two layers? The proper way with a block lintel would be a 16" high lintel block, which is 8" long in the wall. Depending where you are, you should be able to get a 12" wide x 16" high x 8" long lintel block.

It sure looks like he has an 8" wide cast in place concrete lintel sitting on the 12" wide block wall, unless I am reading you wrong. Is the wall actually reinforced or is just the cores on either side of the door reinforced?

The amount of steel in the bottom of the beam(lintel) would be about the same for any 16" deep lintel. The stirrups sound like a little much, but who knowns?

Everything boils down to the roof load (DL, parapet, snow, activities, etc.) and the possible uses if the area if it is a flat roof. Depending on your location, you could also have seismic.

As usual, the curse of the parapet is probably part of the problem (2' of catilevered reinforced 12" block is 300 pounds per foot).

You should question him on the practicality of the design and see what the options are. He has the drawings for dimensions and should know what materials are available locally.

Dick

eamesdaedelus
02-09-2007, 03:11 PM
Actually we are working with an 8" thick wall now.

There are no permit drawings as we are out in the country, and I am the architect and GC on the project.

It is new construction.

There are no roof loads, but there is a shallow roof deck behind the parapet (6'- 8" deep). All of those live loads and dead loads are accounted for in the calcs. No snow, no seismic (this is in central Texas)

We're reinforcing vertical cells in the wall every four feet o.c. so we don't have the full weight of grouted block above the header.

I was intending to use lintel block as the lowest header course, with rebar in that course, then a course of RS- bondbeam blocks as the second layer with rebars there, then grouting all of that solid, to complete the header.

There will be two reinforced cells on each side of the door opening.

I've looked into what blocks are easy to get locally, and we can pretty much get whatever we want as we have a local FeatherLite plant.


What is the proper orientation of two rebars within an 8 wide" lintel block header. How do you get the two bars towards the bottom of the "U" where they'll do the best work in tension? The lintel blocks I've seen all seem to have a pretty narrow hollow as it gets towards the bottom of the block.

Thanks for all of the help. I'm big in understanding how these things are done by the guys that do it every day, not how my engineer thinks it should be done (since he doesn't do much block work...)

Mark

MCC
02-10-2007, 05:31 PM
Do They Have A 16" High Lintel Block Avalable If The Do Its Easy To Grout And Place The Rebar Exactly Where Yo Need It The Grout To The Next Layer Of Rebar.

eamesdaedelus
02-10-2007, 05:37 PM
I'll see if they have a 16" lintel block. That will probably be the easiest for my mason to deal with, as he'll have an open cavity to deal with.

Thanks,
Mark

MCC
02-10-2007, 05:49 PM
Good Luck Hope It Goes Well