Residential Garage Lintel

[ncsueng]

Designing a garage lintel. Simple gable roof. Garage is 26' x 30'. Garage door lintel span = 18' and is on the gable end. There is a floor above, but floor joists are parallel to lintel, so not picking up floor load (are at least ,minimally picking up load).

If I use a steel lintel with plate to support brick, how should I support it? Just some jack studs and king studs? And if so, just use lag bolts down through the bottom flange into the jack studs?

Anyone have better, reasonable ideas?

 

[Ron]

Your primary lintel is within the wood frame. That can be any section that will carry the load...LVL, triple 2x12's, etc. The ledge to carry the brick should be an angle (typically 6x6 x 3/8"), attached to the lintel and also minimally bearing on the brick at the edge of the openings, just to mitigate minor twisting.

 

[EngineeringEric]

Don't forget the effect of torsion on your beam. With a span this size i wouldn't want a loose lintel, use a fixed lintel.

 

[ncsueng]

a little more info.

The bottom of the floor system is around 11'-0". The bottom of the lintel is about 8'-0". So I was wanting lintel to carry wind load to the jambs (which carry load up to floor diaphragm and down to slab on grade).

So basically lintel is independent of floor diaphragm and must carry brick and wind load (no floor gravity load). In otherwords, there is a pony wall on top of steel lintel, up to floor diaphragm above.

 

[msquared48]

Well, in all probability, the lintel will soon no wind load from the door, only about a foot of the three feet above it. I would be far, far more concerned with the load from the brick and limiting the deflection of the lintel over the door to keep the door operable.

Mike McCann, PE, SE (WA)

 

[KootK]

I'd put end plates on the beam that extend above the top flange such that lag bolts can be installed into the king studs. Firstly, I think that the king studs is where you want the torque to go. Secondly, you'll deliver the torque more convincingly if you spread your fasteners out a bit. I'd recommend the same for Ron's idea which would be my first choice if the numbers work.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

@Ron;

Why a 6x6 lintel? That would stick out from the brick with the typical 1" air space. Also the torsion on the wood beam would get pretty high if you used a larger air space.

@Kootk - I assume you are talking about an I-beam. If so, how do you get the torsional deflection numbers to work out?

I dislike designing these things as you can never really get the torsion to work out even thought they seem to perform OK in practice. Seems the only way to really get the numbers to fly is to put kickers on the back side of the beam (of course the contractor will not appreciate that)

 

[Ron]

XR250....if you specify a 1" air gap for the cavity wall, you'll get no gap in many places. I do not specify a 1" gap...usually 1-1/2 or 2". Since the height above the ledge angle is limited, and the angle is robust, the torsion on the wood section will be tolerable. If the torsion is too high, the wood section can be flitched on its back side to assist.

I agree with KootK's comment about the end plates.

 

[KootK]

@Kootk - I assume you are talking about an I-beam. If so, how do you get the torsional deflection numbers to work out?

Sometimes I don't. If I have to start thinking HSS lintels, I'll usually consider it time to start thinking HSS posts as well. Then the connection between the two is relatively easy. I don't like designing these much either.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

 

[XR250]

@Ron;

Many times I work on houses where there is 10 to 15 ft or more of brick above the lintel - hardly limited. (basement garage on two story house).

@Kootk;

I have gone the tube steel route as well. Fortunately, most houses I get are not brick veneer or I think I would shoot myself.

I once talked to a tech rep from the brick institute and he agreed that these things really don't work out easily. He recommended putting joint reinforcement in the first three courses to provide a pseudo-reinforced masonry beam. In reality, I think the brick just acts as a deep beam or we would see lots more problems with these. I guess that is why most masons around here put a jack under the middle of the long lintel while they are laying brick.

 

[Canuck67]

I design supports like this often. For this span, predominate method is to design a steel beam with steel plate welded on the bottom. The steel plate supports the brick as a ledger and the steel beam supports the brick load and wood structure load. In all cases, if we are using a steel beam with plate, we support it on steel HSS columns. The top plates of the HSS columns are welded (less often bolted) to the underside of the bottom flange of the steel beam.

While it may be possible in some cases to justify with theoretical calcs that a timber or multiply wood column can support the loads (long term factors for brick/dead loads), remember that brick veneer is sensitive to deflections and creep which can result in cracking. With a steel HSS column costing $125 each, tough to justify otherwise on an economic basis. Tying the beam and columns together with welding helps restrain the tendency to rotate at the ends.

 

[XR250]

@CAnuck67

What braces the top flange of the i-beam?
If the columns are fastened to the underside of the i-beam, how is the torsion resolved? Seems you need the top flange attached as well.

 

[jayrod12]

I would likely be putting a bearing angle at the floor level fastened to a built up rim board that is blocked back a few bays. This eliminates the torsion and also significantly lowers the load to be seen by the garage door lintel. Then I don't worry about using a wood lintel with wood kings and jacks and another brick ledge angle. If your upper angle is 1/4" thick or less then they can even put mortar in the gap in front of it to hide the fact it exists.

 

[Canuck67]

@XR250,

Often there is a floor framing into the top of the steel beam where the floor joists are perpendicular to the steel beam, plus a wall on top of the floor framing which further adds some restraint. In your case, this does not appear to be true as the floor joists are parallel to the beam, however, you could consider re-orientation of them, or perhaps just the first few feet.

You may want to review technical note 31B from the Brick Industry Association - "Structural Steel Lintels". This document has some informative comments on lateral support and torsion of steel lintels supporting masonry brick.

I do like the idea of end plates suggested by kootk, however, I have never seen anything like that in practice and the prescriptive tables in the Code do not require it for up to about 18 ft. spans.

 

[Ron]

XR250....yes, the height of brick can be significant, which is why you should check the torsion; however, it can be accommodated once you know what it is. A 6x6x3/8 angle will handle a substantial brick load. You can also provide an intermediate ledge angle to reduce the load on the primary one.