Concrete lintel

woody7777

I have just had a handyman install a concrete lintel over an internal door for me to replace a wooden one. A friend told me to make sure he knew which was the top side, but when I put the question to him he replied that there is no top or bottom and they go in either way up.
Is this correct?

daveyjp

Depends what type of lintel.  Some have the rebar off centre and the shortest distance to the edge should be the bottom.

tacpot12

It depends on the design of the lintel, and specifically the location of the reinforcement of the lintel. It would be as well to check with the manufacturer.

You should think about the fact a concrete lintel that has a rectangular cross-section can be installed in four different orientations, at least two of which will not allow the lintel to support the maximum load that it has been designed to support.   

The handyman might well be correct - he may know that  that specific design of lintel can be installed either way up because the reinforcement is located in the centre of the lintel and he knows that the reinforcement is laid parallel to the plane of the top and bottom surfaces.  

grumbler

If the  pre-stressed steel bar is in the middle of the lintel (you could see it on the left and right sides), then  there is no top and bottom. I am yet to see a lintel with a bar not in the middle.

woody7777

The lintel was smooth on one side and rough on the other. I thought the rough side might be the bottom to help hold the plaster in place.

grumbler

woody7777 said:

The lintel was smooth on one side and rough on the other. I thought the rough side might be the bottom to help hold the plaster in place.

Usually it's some frame, not plaster. Some people say that the rough side is for the bricks above, but IMO it's just unintended result of the technological process - free top surface of concrete in a mould.

stuart45

The rough part is the top on a composite lintel. It helps tie the 3 courses of brickwork needed before it can take any point loads. Ideally the beds would have brick tor in so the lot becomes one lintel.
A non composite lintel can take a point load directly.
Concrete lintels should be checked for a camber built into them, and this tells you which is the top, when the rebar is in the neutral plane in the centre. Years ago the top was marked. 
Insitu ones had the steel in the bottom part of the lintel.
. 

woody7777

I am a bit confused now. Grumbler says there is no top and bottom and stuart45 says there is. Who is correct?

Section62

woody7777 said:

I am a bit confused now. Grumbler says there is no top and bottom and stuart45 says there is. Who is correct?

Both are.

It depends on the type of lintel.

Pre-stressing the concrete means the reinforcement can be in the centre - so the lintel can usually be used either way up.

Concrete with simple reinforcement has to have the reinforcement at the bottom - because the bottom of a simple concrete lintel is usually in tension when loaded, and therefore the steel is required to prevent cracking.