strength of concrete lintel

[treecott]

Hi all, new to the site, and I have read quite a few lintel posts. I am wondering if someone can help me with my problem.

I am doing a loft conversion, and steels are in supporting the roof etc. I have a large square bay window, with a concrete lintel over it. It is an 8ft window, and it goes pretty much up to the ceiling. There is approx 8/9" plastered,above the window (presumably the concrete lintel, and then some brickwork above ceiling height).

My question is I have now come to put the new floor joists in and I have to bolt 8x2 timber to the wall above this bay window, and attach the 8x2 joists in joist hangers off this timber. The property is a bungalow, and the roof overhangs the bay window slightly. There is very little brickwork above this bay window. I have bolted the 8x2 wood to the wall, and the joists are in. My worry is no-one from Building Control has mentioned about the concrete lintel being adequate to take the load of the floor. Neither has it been mentioned in the S.Eng. report. Who checks to see if the lintels are adequate? As this is a large span, could anyone tell me whether concrete would be ok, or will it have to be changed to a catnic lintel.

The steel is holding the roof up, so there is less pressure on the concrete lintel, however, the existing ceiling joists are set into the wall above the lintel, and as it is such a large opening, to have concrete lintels (which I presume there are two, one innner and one outer, should I be worried?

Any advice would be gratefully received.

 

[Shytalkz]

Sounds like the intention of the SE was that the 8x2s bolted to the wall support the load from the new joists. There is no additional loading (or even reduced loading) to the existing lintel, thus, no need to check it, assuming that it was ok before any of the work was carried out.

You need to check with the SE if you have any concerns.

 

[Agile]

I dont fully understand what you are saying.

However, the strength in a prestressed concrete lintel is not primarily within the lintel itself but in the brickwork above it as it effectively forms a composite beam.

Thats why you cannot support anything directly on a prestressed concrete lintel.

If you still have any doubts imagine this window to be on the ground floor with three stories above it.

Tony

 

[Shytalkz]

Not necessarily true Agile: some rely on composite action, others don't.