Eurocode 5 span tables (Using)

[chirpychippy]

Good morning.

I have got the Eurocode 5 Span tables 3rd edition. From this I am trying to fathom a joist section size for a certain span but am struggling to interpret the tables.
The project is a snooker room set into the corner of a warehouse with two stud walls at 90 degrees to form a box or a room.

This is my conundrum:

The joist span unsupported is going to be 6200mm. So I need a joist that will span this distance, the only sizing that gets anywhere near is 47x220 which will span 5.83 at 400c/c. This sizing to me is unrealistic and therefore I would like to reduce the depth by introducing a binder or two, however the binder will need to be 7.2mtrs unsupported*

None of this, despite not being able to understand the span tables, seems feesible. To digress the wall supporting the ceiling joists at one end will be a 4x2 stud wall at a height of 2.6mtrs, the other wall is concrete. I could increase the section size of the stud wall to 5x2 or even 6x2 but the main aim of this project is to keep the material costs as low as possible whilst maintaining a safe structure.

* The binders can be supported from the concrete roof above with struts.

So I envisage bolting a plate or two at 7.2 meters to the concrete ceiling above directly above the binders which will also be 7.2mtrs, these will be skew nailed to the ceiling joists. then I drop struts down from ceiling plate to the binders and side of joists at "say 1.2mtrs c/c and bolt using timber locks. The finish to the underside of the ceiling will be 9.5mm plasterboard and skim.

But I still don't know what size binder or joist will be adequate, could anyone offer guidance please.

 

[chirpychippy]

anybody, there is quite a lot in this book I don't understand?

I am of the inclination to use 8x2 c24 and brace from ceiling above. But if I were to do it from the book then I should be using something in the region of 12x2 c24 for .25kn/m2 which to my mind is ridiculous.

Please, what is the difference between .25 and .5 kn/m2 as in what is being allowed for bewtween the two. Thank you Chirpy

 

[theoldun]

Please, what is the difference between .25 and .5 kn/m2 as in what is being allowed for bewtween the two. Thank you Chirpy

Quick answer 0.25kn m2
Busy next couple of days, will come back to you.
Regards oldun

 

[catlad]

If this is just to support the ceiling without it being used for a floor, and you are to drop some wires down from the concrete roof above to strap to the middle of your ceiling to help prevent it sagging then I think 8"x2" will be ok if you can get those lengths.

 

[theoldun]

Chirpy,
Had a few spare minutes, so before you gert your knickers into a twist, google

Ecojoist® Technical Manual.pdf - Robinson Manufacturing.

Then google and find both Eco joist and Posi joist local manufacturers and ask for a quote from both for joists the overall span you require, the number of joists you require at 600mm centres, with no imposed load, no floor load but just a 15mm plasterboard and skim and quilt insulation
Total load 23.7kg m2, call it 0.23kn m2. Let me know how you get on/ For that loading they will make you up a joist approx 9m long.
Regards timber joist not being long enough, we do not think you would be able to source that length.
Regards oldun

 

[chirpychippy]

How bizzare catlad I was just googling that option using wires when I thought let's see if anyone has replied, it is an option but length of joist is a problem at the moment, they want to use for storage on top, but its just not ffeasible.

Cheetrs oldun, Sunday is my knicker wearing day and there nnot in a twist, thank you for the info will get on to it right now and let you know.

 

[chirpychippy]

Hello oldun, I can get 12x2 at 6.6mtrs coming in at £1200 for 19 lengths at c24! I rand local supplier of posi joist and they suggested PS10 at 600 centres would be fine and quoted £880 inc. But on checking their span tables its not big enough so am now waiting a resived estimate with correct size joist.

Could I? Put a double 12x2 across centre point of the length then hang 7x 2 off of the double at 90 degrees. The spans for the 7x2 C24 would be 3.9 clear span, left and right of the double?

 

[catlad]

You could stiffen those 12"x2"s by adding a steel plate and making a flitch beam, but why not just use a normal steel beam?

 

[theoldun]

Chirpy,
Suggest you wait for revised quote, as still think it will be cheaper than solid timbers. If you use solid, you have four rows of herring bone or solid noggins, binders and any possible hanging from concrete roof
Also remember that Posi Joists are two thirds labour content cheaper to install.
Have given fair bit of thought to this and if solid works out cheaper, then will make suggestion to you best way to go.
Regards oldunI

 

[chirpychippy]

Cheers Catlad, considering all options available and not discounting any at the moment, a steel could be a solution and I was thinking along the line of a 152x152 uc23 beam, but once again I cant work out the loadings for a beam, let alone for 6.3mtrs.

Oldun, I am waiting for a revised quote from Donaldson Timber, but whilst initially giving me a figure over the phone for the wrong size posi joist they are now saying that I shouldn't have been given a price over the phone as all their estimating is done by e-mail and that they have a two week league time on estimates. I think this is bl**dy ridiculous and am waiting a call from another supplier.

Hay ho, wait and see, thanks for your help. btw I am not going the route of bracing it from the concrete ceiling above, I don't even know if it can be drilled.

 

[chirpychippy]

Got a price from Travis Perkins today don't know who they went to for price but whoever it was specked this posi joist for span I am bridging.............

304 X 122
DL 22KN/M2
LL 1.5KNM2
SPACING 400 CC (According to them)

I asked for ceiling joist with the loads you specified Oldun and the above is what I got,

Grand Total inc VAT £6612.

Take that back it is Donaldsons Timber Engineering.

 

[catlad]

You must be looking at it upside down its £2199

 

[chirpychippy]

Well, not quite right I added the vat twice but still comes out at £4332.

Got price from Raeltd today Specking the following:

304 x 72 at 600 cc
Top dead 0.510kn/m2
Bottom dead 0.132kn/m2
Snow load? 0.600kn/m2

£704.75 + vat for 13.

Oldun whilst these loadings differ from yours are they within the tolerances you sspecified, please, thank you.

 

[theoldun]

Chirpy, We are never going to educate you by just keep telling you how to do it, so we are now going to make you fathom it out your self.
Go back to the technical manual page 20 read and understand dead loads and live loads 1500 N/m2 = 1.5 kn/m2. .250 N/m2 = 0,25 kn/m2. Okay, so far.
Now take take price of £4332 and ask your self why they have included a live load of 1.5 kn/m2 when you have no live load. We suggested a dead load of 23KN/m2 and they have given a dead load of 22kn/m2, so there are only coppers in dead load.
Regards quote of £704. plus Vat, is getting near the price we would expect, how ever why have they included a snow load?
Now go back to manual and read page 19 and then 20 and note the conversion factor at bottom for kg/m2 to kn/m2. We use the factor of 10 as it is easier
QUOTE Oldun whilst these loadings differ from yours are they within the tolerances you specified, please, thank you.
Chirpy you should now be able to answer your own question.
It would appear son, that either the manufacturer has not understood your instructions, or you have given wrong instructions.
If you go for last quote, make sure it is in writing and designed to your instructions .Any problems lad then come back as there is another more costly way round it.
We are still not sure of size of room
Regards oldun

 

[chirpychippy]

Oldun I am getting really frustrated with this dead load live load, I understand the difference between dead load and imposed load. I have looked at the calculation of say plasterboard at 12.5mm. So ive got 11.2kg/m2 x 9.81 = 109.872 kn/m2, so is this .109kn/m2 for plasterboard?

The room size is 7200mm long by 6300mm wide hence shorter span for joists. Imagine a rectangle! 2 long sides 2 short sides, 1 short side and 1 long side is concrete walls which form the rear corner of the warehouse, the other long side and short side is going to be 5x2 stud walls at 2.7mtrs in height, this forms the room in the corner of the warehouse.

I think we have got to the bottom of this now, I asked to speak to someone else and went through it all again. The joist size now is 253x97 not 304.

Nonetheless, I really still am at a loss with converting kg/m2 to kn/m2, what does to the factor of 10 mean?

Thank you.