Workshop Mezzanine Build Theroy Request

[Togalosh]

Evening Gents,

I am due to move to a big, empty & tall industrial unit to set up a new workshop with other makers & although it is much bigger than what we've been used to we still need to maximise on floor working/assembly space so a few mezzanines will have to be made. However I am not sure that I know how to go about it in the correct way so I am after some advice please.

I built a mezzanine in my current workshop, based on my floor joists of my Victorian house, which seems perfectly secure to me & hasn't made me doubt that at all in 5 years with plenty of Oak stock stored on it. The landlord of my current unit is a structural engineer & he is happy with it ..but then he was happy to use carpet in a ceiling for insulation purposes regardless of fire precautions. I made it from massive salvaged 'pine' packing crates which are of mixed quality with regards to any construction grading. Each 'plank' is approx. 8" x 2" at 450mm centres spanning 3m with 18mm ply on top with no noggins & between stud walling. I used 3"x6" as legs/uprights at each joist which were nailed to the stud walling. Does any of this ring alarm bells? If not I could copy this again as hopefully I should still be able to get as many van fulls of this packing crate timber as I can manage (we gave up at 4 very full van loads last time). I could double it up if it is of doubtful quality.. or is it not that simple?

So:
What quality/grade joist should I be looking for ?
How can I work out the maximum span for the material I can get ? A 3m span seems useable but the crates are 4 to 5m long.
How can I work out the dimensions of any upright supports/legs ?.. would making I beam like legs from thinner stock work ?
Should I use noggins between joists or will ply do the same job ?
I am planning to brace the corner sections to stop any racking (?) but what length should the braces be - does it matter ?
Floor fixing plates- any recommendations? I was going to copy those used in large warehouse racking.
Are there any gaps in my thinking/plans ?

Any advice would be much appreciated.
Togs

 

[Doug71]

What you are thinking sounds ok but mezzanine floors normally come under building regs. Would be worth checking the current regs for joist sizes, fire regs etc or even getting some plans drawn up, you should really be putting in an application and telling them exactly what you are proposing by submitting plans etc.

I know most people wouldn't bother but I always think it's worth doing things like this properly these days for peace of mind.

Doug

 

[Armagh]

Type "joist span tables building regs" into Google and you'll get all manner of informative charts.

I'm pretty sure that with construction grade timber that's stamped c24 you can achieve spans of up to 4.6m spaced at 400mm centres if you use 9x2s. Noggins must be at least every 1500mm I believe. There's room for manoeuvre too. You can achieve larger spans if you space your joist more closely, or use heavier sections of timber. If you're speaking of a smallish span like 3m then 8x2 timber is certainly enough, but you'd want noggins in the middle.

 

[Lons]

I'd go with what the others said but especially be careful about regs as it's presumably a commercial environment and should anything untowards happen, the HSE will be down on it like a ton of bricks. I doubt they would be happy about ungraded timber though doesn't mean you can't use it.

One thing you need to be aware of is that when calculating loading it's not just about size of timber section but weight also as the construction has to support its own weight as part of the loading. Noggins are a must IMO.

Bob

 

[DoctorWibble]

Noggins make a big difference. They share loads between joists. Whatever you do include noggins. They don't cost much and are easy to install.

And best use structural graded timber. Its not expensive and makes it easy and safe to design. The alternative is over-building with cheaper timber of an unknown strength which is actually likely to cost more in the end and can give you no certainty even then. And if anything did go wrong you'd have serious insurance /liability issues.

And use the on-line span calculators as has been suggested by others.

 

[Sawdust=manglitter]

:shock:

As a structural engineer seeing things like this makes me wonder how things dont fall down all the time!?

It sounds like it will require building control's involvement, particularly as it's in a commercial setting. This will also involve getting design calculations undertaken by a structural engineer to satisfy building control. Getting building control and a structural engineer involved might seem like a waste of money to some, but its all required for good reason. God forbid that something were to happen, but its not just for yours and others' H&S, your insurance would also be void.

To start with, you should be using structurally graded timber (for example C24 grade). The sizes/specifications will also depend on the proposed usage and loading (which will make a drastic difference), i.e. only for timber storage, will that also include man access to access stored items, or storing any machinery/heavier goods, will there be shelves and if so how high (max capacity), etc. A bit more info, and better still a sketch, will give a better idea of what may be required.

Also FYI, span tables will mean nothing for your purposes as they will all be based on domestic loading!

 

[Togalosh]

What you are thinking sounds ok but mezzanine floors normally come under building regs. Would be worth checking the current regs for joist sizes, fire regs etc or even getting some plans drawn up, you should really be putting in an application and telling them exactly what you are proposing by submitting plans etc.

I know most people wouldn't bother but I always think it's worth doing things like this properly these days for peace of mind.

Doug

Thanks Doug, that obviously never occurred to me.

 

[Togalosh]

Thank you very much Gents,

As ever more brains make more sense.. it seems that it was a stupid idea to use the salvaged wood, especially as it wouldn't save me much (if anything) as the time it would take to fetch & break it down would outweigh any financial saving if structural timber is cheap enough. I thought it was quite expensive...

I don't intentionally cut corners & certainly do not intentionally do shoddy work so I will be retro fitting noggins to my 1st mezzanine asap & definitely before I move out. 3 long served builder/carpenters who saw what I was doing did not raise any concerns about it. If they had I'd have followed their advice. I have no qualms about calling building control either or over specifying the materials to be used. I'd rather not have a mezzanine than have a shoddy & dangerous one.

It will be tricky to work out what weight will be stored on it (oak stock of various sizes &odds & sods of furniture waiting for reassignment) but I will over estimate it & yes I will have to get up there to get at it.. It's just for storage so no machinery as such will go up there just the odd rarely used power tool perhaps. A sketch could follow when I actually get into see the new place & work out my space within it.

Sawdust: you say online span charts are usually for domestic loadings.. why is weight treated differently in domestic & industrial settings ? Weight is weight no ? If I used 9"x 2" joists as mentioned by Armagh for a 3.5m x 3.5m platform with timber stacked no more than 1m high would that be considered to be a substantial structure or the minimum required for any loading ?

Togs

 

[Sawdust=manglitter]

Sorry, I didnt mean to imply that you cut corners or shoddy workmanship! In work i just see thing daily that have been standing for a while yet could never be proven to work in calculations! But thats why we use factors of safety in our calculations to ensure that nothing untoward occurs.

In terms of variations in loading, we undertake our calculations based on design standards (british standards or eurocode), so we cannot deviate from these standards. Just to give you an idea, please see below load tables for various situations which we are required to use. Note that the domestic joist span tables are ALL based on the very first values of UDL=1.5 kN/m2 and a point load=1.4kN. Note the massive variations in different situations.

Just to give you an idea, assuming Oak has an average density of around 800kg/m3, a stack of 1m tall and 1m wide would be the equivalent of 8.0kN/m2, which in comparison doesnt come close to most of the loading shown in the above tables. I was just saying that it should be designed appropriately by a structural engineer.
(Dont mean to scare you though!)

 

[TFrench]

Used industrial mez floors can be had on ebay for relatively cheap - stronger than wood and it'll go together much faster which is what you want if its a commercial environment.

 

[Togalosh]

Sorry, I didnt mean to imply that you cut corners or shoddy workmanship!

I didn't take it that way so no need to apologise.. I was expressing surprise & disappointment with my own work & lack of thinking...

I see gas "unsafe situations" almost daily which make me wonder how no one has come to harm. People are so careless, it's like watching Evolution By Natural Selection taking place right in front of me.

Thanks for the tech data. Lots to think about.

 

[Togalosh]

Used industrial mez floors can be had on ebay for relatively cheap - stronger than wood and it'll go together much faster which is what you want if its a commercial environment.

Ha, again something I never considered. I will check that out.

Nice one TFrench.