RSJs too big?

[JDLDIY]

I'm having a door moved to butt up against a window, the new opening in the wall will be some 4m in length. We tried to find a lintel to cover the length but it's too big, so we had to opt for 2 RSJs, sledgehammer to crack a nut etc I know but there you are....

My question is that the RSJs are sitting in my driveway waiting for the builders to arrive in a weeks time and I've measured them at 145mm wide. So, bolt the 2 together and that makes 290mm, which is fine apart from the wall is only 260mm!! I have said that I'm going to render above the window and door, but how thick would render normally be?

I would really like any pointers/guidelines on how RSJs should be installed, so that I can keep a watchful eye as the job is being done and ask the right questions. I'd also like to know whether RSJs come in standard sizes and if so what they are. Could the steel yard have got the order wrong?

Cheers

JD

 

[jeds]

Not RSJ's JD - Universal beams!

They do come in standard sizes but there are millions of sizes. The narrowest - from memory this mind - is about 102mm. Might be 80MM?? Anyway, they come narrower than 145mm.

Steel stockists often don't have the size you want and it is usually a compromise. If they do have the size you want but also have a close off-cut they will have told your builders that the proper size one will have to come from a full length piece and that they will have to pay for the full length plus a thousand pounds for cutting. The builder will take the off-cut every time.

You could have used a pre-formed lintol - anything up to 5 metres+ in length! Expensive though.

Was this beam not specified? if it was you would know exactly what size to expect - not trying to save the cost of professional advice are you?

The end bearing should be a minimum of 150mm. It is common practice to sit the beams on the end bearing, lay a mortar bed on top and then wedge them up against the underside of the wall being supported. That's OK but make sure they don't pack the end bearing with anything that will compress or rot - like wooden wedges for example.

 

[JDLDIY]

Sorry if I've used the wrong terminology, many thanks for your reply Jeds.

Was this beam not specified? if it was you would know exactly what size to expect - not trying to save the cost of professional advice are you?

well actually yes I am getting around having professional calculations done as it happens. I know I should be heavily criticised for this, but in this case I believe I have made the right decision. We looked into the cost of a proper lintel but catnik gave us the price of a special one off, which was much dearer than the route we have chosen. We would definitely have needed proper calcs in this case as the floor weights etc would have been crucial. Another company (their main competitor) said they couldn't give us a lintel strong enough for the job. The steel we have will "hold up the Mary rose" in the words of the builder and i believe him. He has 30+ years experience locally and multiple recommendations. Building control are happy too. I'm more concerned that it's installed correctly and that we can hide it behind the render.
So, from what you are saying the lintels are jacked up onto the brick end bearings, a bed of mortar laid on top of the lintel and then I guess wedges laid under the lintel to bring it into contact with the upper brickwork? What would the wedges normally be made of then? What should be done about damp proofing? How should the lintels be joined together - they have said they will be bolted together.

Thanks again
JD

 

[david and julie]

Wedges would be pieces of slate hammered in tight and mortared whilst RSJ is jacked up with acro's

RSJ bolted together with long bolts/screwed rod through holes drilled or burnt in the joist.

DPC? is nowhere here, its on the ground about 2 brick courses up.

 

[JDLDIY]

When you use a cavity lintel, the "cavity tray" part of the design takes any moisture to the outside wall. I guess what I was getting at is what is done when using RSJs instead?

Where would these bits of slate come from? I see from working under the ground floor that some of my squeaky floorboards are the result of joists not being in contact with the sub walls, so I could do with getting hold of some of this slate to wedge in the gaps.

Thanks again!
JD

 

[david and julie]

usually pieces of roofing slates.

 

[jeds]

You are quite right, some lintols are shaped to do the job of a cavity tray. With a UB you don't have that shape so a pre-formed tray should be (is often!)inserted somewhere above the beam.

Speak with your building control inspector and ask him/her to explain what system is being used and how it works.

 

[JDLDIY]

Ahh...I see. Thanks, I will be having a word with the builder about that. What are these "trays" made from and how are they installed? God I'm nosey aren't I?!
JD

 

[david and julie]

I have a feeling that your builder will flood the job with manpower!!

 

[jeds]

Usually made from black plastic. Sometimes stiff, sometimes flexible. Some have lead flashing attached.

It also depends on the amount of wall above the beam and the exposure. If you have very little wall and it is sheltered it may not be necessary to have a tray at all.

Building control will soon tell you if they think its necessary. If they say it's not just ask them to explain why?

 

[JDLDIY]

I have a feeling that your builder will flood the job with manpower!!

What to get away from me as quickly as possible?
Wouldn't be surprised!!
JD

 

[ademac]

footnote: BCO will probably tell you to support the ends of the beams on concrete pads i.e. concrete bricks/blocks built in prior to fitting the beams.

 

[JDLDIY]

Yeah, padstones I think they call them, the builders fitted them as a matter of course. They used concrete slabs, looks very solid I must say, used half or third bricks to cover up from the front.

Cheers

JD