Ceiling joists and u beams? Is this what you would do?

18 Dec 2006
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United Kingdom
I am currently having a small extension made to the rear of my property which basically consists of knocking down an old conservatory, rebuilding in the same footprint an extension with a flat roof. The wall between the lounge and conservatory is being removed - so effectively I am creating a larger lounge.

Now the SE has come up with calcs showing that I need a couple of U Beams bolted together ( 300 x 90PFC ) to support the rear upper wall.

I left this for my builder to do last week whilst I've been away. Today, on the inspection of the work The Beams have been put in place. The existing ceiling joists are now resting on top of the Beams. This means the Beams are 300mm below the existing ceiling level which just leaves 2030 from floor to the underside of the Beams. Adding a wooden floor finish will reduce this height too.

Now I was under the impression that I was going to have a continuous flat ceiling from the old lounge all the way through to the new extension but now I've got this horrendous partition half way across the room.

So, this may need a rethink as most of my mates are over 6ft tall and will probably need to crouch under this beam when walking across the room.

I was under the impression that the joists could be placed into the U Beam or hung and made secure thus reducing the height of the Beam showing in the room?

Or is there any other way of reducing this eyesore cutting my room in half?

I have spoken to the builder about it and he says that the existing ceiling joists have to sit on the Beams and there is nothing he can do about it as the Beams are the correct ones as specified by the SE.

I'm not a builder so any advice and thoughts would be so welcome.

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your builder is correct. or he has done it in the way that was specified.

you can sit joists into the web, but this would involve a LOT more work and is a lot more difficult to do.

collecting the joists on TOP of a beam and then jacking that beam snug is a far more reliable way of supporting the floor and wall above than trying to feed a beam in at floor level.

did you specify a hidden beam? were both options offered to the builder for quoting? would you spend an extra £1800 - £2500 for the privilege.
Thanks noseall,

I asked the builder when quoted for a continuous ceiling all the way through. With this Beam slicing the room in two the room looks quite ugly now.
I will talk to him again tomorrow when he turns up and try to remedy this situation. The existing work he has done so far is extremely good and he has been professional at all times. It's a shame that this problem has arisen when things were going so well.

Looking at the plans he has followed the drawings and calcs as far as i can see. Perhaps I should have studied them a bit harder but I'm not a builder and probably wouldn't have spotted this mistake anyway.

Thanks again anyway,

you say you asked the builder for a continous(sp) ceiling, but then say he has followed plans. Did you give him the same plans when he priced it?
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Joists can sit in the web (or be hung off the top of the beam) to make a ceiling flush - this is what I normally specify and make it clear that the builder is to price on this basis.

But it is much easier for the builder to put the beam below the joists. However, its not correct to say that the joists have to sit on the beam.

Check the plans and check the engineers spec. If a flush ceiling is not mentioned then why not - did you ask for one from the outset?

300mm deep is a massive drop. Why couldn't the engineer calculate a beam less deep?

Either way, someone is not being fully professional. A 300 deep beam with only just over 2m headroom is obviously going to be a big issue to a client. I would expect the designer, the engineer and the builder to realise this and confirm with you, the client, if this will be acceptable.

IMO, its not acceptable for the builder to blindly carry on and say "Oh well, thats what is specified". If the engineer had specified a bit of 4x2 for the beam, would the builder have put that in? Ask him.
When I came up with the idea of the extension I got the builders round to quote and also draw up plans etc. I specified to the builder that I wanted continous ceiling.

The calcs came back from the SE specifying these deep Beams probably because the opening is 6m wide!

The builder drew up the plans but looking closer it doesn't actually state that the Beam will have the joists on top etc.

I thought that the joists would be placed into the web of the beam and noggins placed to prevent twisting?

I've come back home to find the joists on top of the Beam and the builder is telling me that this is the only way the joists can be supported by this type of beam. Is he right or can the joists be fixed into the web of the Beam?


Thought I'd show you some pictures of the Beam and how deep it looks from the ceiling height.
From the floor to under the Beam is just over 2m but this doesn't include the wooden flooring and Beam cladding.

Is there any Building Regs objections to placing the joists into the Beam Web as long as noggins are used?

surely if the beam is 300mm then if placed above the ceiling it would actually also be visable in the rooms above unless the floors are 300mm joists?
This is a real cockup.
I would get a different proffessional opinion on the caculations, even for a 6m wide opening a 300mm deep beam cannot be necessary.
Pay for a good structural engineer to work it out and then sue someone for the cost.
I would guesstimate that a 200mm deep beam would do and there is no reason the joists couldn't sit inside the web.
Somone is having you over mate.
Alan D.
And the slab the beam is resting on looks cuffed, it should be hi density conc or something similar, it looks like a slag block .
..... Is there any Building Regs objections to placing the joists into the Beam Web as long as noggins are used?

...... Is he right or can the joists be fixed into the web of the Beam?


See the first paragraph of post nr 6 :rolleyes:

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