# Floor strength for heavy(ish) machinery



## NickM (9 Mar 2019)

This came up on the thread about the Baileigh table saw review - I thought I'd start a new thread to avoid that one drifting.

That saw weighs around 200kg and in asking how feasible it would be to get it up some stairs to a room above my garage, I was prompted to think about whether the floor will be strong enough.

The set up is as follows:

- Floor joists are 3" x 8" and are spaced at 15" on centres. The span is around 16.5'.
- The floor is 20mm chip board.
- The building is brick construction and the roof is a pitched roof.
- Although the saw wouldn't be right in the middle of the span, I can't get it very close to the wall because of the pitched roof.

The joists seem large, strong and relatively closely spaced to me (but I'll freely admit that I'm guessing...), but I wondered about the chipboard. I could put the saw on another sheet, making sure that it straddles a couple of joists which I think would make it stronger. I might need to be careful if I decided to put the saw on a mobile base because of the extra pressure going through the wheels.

Any thoughts?

Thanks.


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## MikeG. (9 Mar 2019)

Those joists are sized for a uniformly distributed load. They are barely strong enough for that. Whilst 200 kg isn't huge, it is a point-load, and as such I absolutely would not put that weight on that floor (even if you could get it up the stairs), unless the floor was radically reinforced.


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## RobinBHM (9 Mar 2019)

Im wondering if you sistered 3 or 4 joists where the saw will sit, would be ok.

Say with 10 x 2 joists -they dont have to be full length, a foot or so short of each end would work.

If you have some bags of sand or cement around, lay 8 at the spot where the saw will sit and measure the sag.

Note: I agree with Mikes advice, just trying to come with some solutions / ideas, we dont people being stopped from buying new toys


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## NickM (9 Mar 2019)

Thanks. Very helpful.


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## MikeG. (9 Mar 2019)

I'm afraid I think you need some steel in underneath that floor to cope with that sort of point-load. Further, that won't be all that happens up there. You'll bring other tools, equipment, timber etc up in association with the table saw. You'll stand adjacent to the saw yourself. Unless you can get a prop under the floor, I honestly think that steel is your only answer (or a glulam beam, perhaps...just that steel tends to be cheaper).


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## MikeG. (9 Mar 2019)

RobinBHM":3hunzow3 said:


> Im wondering if you sistered 3 or 4 joists where the saw will sit, would be ok. Say with 10 x 2 joists -they dont have to be full length, a foot or so short of each end would work...........



Every structural engineer in the country who sees this is cringing right now!   Seriously, please don't anyone try this at home.


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## Peterm1000 (9 Mar 2019)

Ok - about to show my stupidity. So why is it OK to have 2 people totalling 200kg in a double bed weighing a further 100kg all going through 4 posts, but not OK to have a lighter saw on the same floor? We have even had 4 full sized blokes stand next to each other in one of our upstairs bedrooms and the floor has not collapsed.


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## MikeG. (9 Mar 2019)

A floor isn't judged to be strong enough simply because it doesn't collapse, BTW.

That bed isn't even OK on that floor. The maximum span of a 200x75 joist is 4.83m at 400 C's, with the minimum possible dead load on top. The span is a foot longer than that. So in the absolute ideal circumstance, with the minimum dead load and an assumed domestic UDL on top, that floor doesn't work...........never mind sticking a point load on one or two joists right in the middle.

Besides, those 4 bed posts are each putting down a point load of 300/4 = 75 kg, probably spaced some 1500mm apart and thus putting the load onto multiple joists. The table saw is concentrating its load on one or two joists, and of course it would have an operator standing there too.


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## RobinBHM (9 Mar 2019)

MikeG.":unbta8mw said:


> RobinBHM":unbta8mw said:
> 
> 
> > Im wondering if you sistered 3 or 4 joists where the saw will sit, would be ok. Say with 10 x 2 joists -they dont have to be full length, a foot or so short of each end would work...........
> ...



I cant actually what is wrong with what Im proposing. We are only talking 200kg. Over 2 joists thats an increase in load of 50kg at each end. 

If existing joists are sistered, that would increase the stiffness of those joists. The bending moment near the ends of a beam are very small, so the sistering isnt required the whole length. The only risk is increasing the load on the joist support, but thats only 50kg per joist end -if they are on hangers there would be a big safety margin.

I realise 10 x 2 might not be a big enough section -ive not looked at the span tables, but given the fairly small load and the joists are being effectively double in section, I wouldve thought it ok.

I did think of making a flitch beam of one of the joists, but thats exprensive and a lot of work. A few lengths of joist glued and bolted is easy.


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## MikeG. (9 Mar 2019)

RobinBHM":23g68lwn said:


> .........I cant actually what is wrong with what Im proposing...........



I don't know how much clearer I can make it. That floor is too weak for normal domestic loads. It shouldn't be used as a floor at all. You are proposing to stick a weight in the middle of it, and that will take the deflection beyond acceptable limits. It really is that straightforward. Strengthen the floor from below, or forget the whole idea. It's that simple.

BTW...the hangers argument is irrelevant. The figure that this floor will fail on is deflection. It will bend too much.

-

ETA............oh, whoops..........you were arguing about a short sistering arrangement. Sorry. Then you've got to demonstrate that your fixings can take the strain you are proposing, given that they are the only thing taking the deflection. Span tables aren't going to help you, because they work on a simply supported beam principle, and yours has no end support.


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## NickM (9 Mar 2019)

MikeG.":23avrmnx said:


> RobinBHM":23avrmnx said:
> 
> 
> > .........I cant actually what is wrong with what Im proposing...........
> ...



In fairness to Robin, it’s not his floor. It’s mine, so I suspect he has already forgotten about it!

Anyway, I appreciate the input. I need to have a think about what to do.


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## Peterm1000 (9 Mar 2019)

MikeG.":f5uror1q said:


> A floor isn't judged to be strong enough simply because it doesn't collapse, BTW.



Thank you - I don't claim to be Einstein, but I had that bit figured out!   

I think you saying that floor isn't strong enough to have anyone stand on it let alone put the equivalent of 2 people in the middle of it... I suspect there are multiple houses out there like that today that haven't had someone fall through the floor yet.


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## Trevanion (9 Mar 2019)

I know someone with a pretty similar setup with 10" x 3"s on 16" centres and 20mm chipboard on top on about 2 20ish ft spans between the walls and middle beams in the top of a sheep barn. I know that his his Wadkin DM morticer is in excess of 300kg, I think the Dominion Morticer that sits right next to it is over 400kg, then there's a 4 sided planer moulder in there which I think was about a tonne and a half, then there was a seriously heavy spindle moulder that was well over a tonne not too far away from it either. Plus a few other machines in the 100-200KG range. In all, there are several tonnes on these timbers and the deflection is almost nil.

Not sure if that helps you out at all but I'm sure Mike's maths make sense, it's not my field of expertise so I won't comment.


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## NickM (9 Mar 2019)

Thanks Trevanion

I’m certainly not planning to load it up that much! I couldn’t get that sort of machinery up there even if the floor was up to the job!

Anyway, the diet starts tomorrow (homer) ...


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## MikeG. (9 Mar 2019)

Nick, you are being very selective in who you listen to. You seem only to hear those people who say what you want to hear.


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## sunnybob (9 Mar 2019)

I have no technical advice to give, I dont know right from wrong, but I do have to mention a point that many people dont consider in situations like this.
Insurance claims when it all goes runny on you.

Assuming Mike is quoting building regulations, then anything less than his dimensions will render your insurance null and void when (IF) it falls through the floor. Property and people damage will come squarely back to the person who decided to ignore building regs. Insurance companies always have a good laugh when told that so and so did that and it worked for them.
Thats all. Its your house and your machinery.


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## NickM (9 Mar 2019)

No, I’m listening to everyone. Particular thanks for your considered and expert input. I’ll certainly be having a look to see what I can do in terms of reinforcement/re-thinking. 

Thanks again.


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## Peterm1000 (9 Mar 2019)

MikeG.":1afqk3a8 said:


> The maximum span of a 200x75 joist is 4.83m at 400 C's, with the minimum possible dead load on top. The span is a foot longer than that.



I was really surprised by that comment so I looked in the building regs (we just had a big extension built). That's what it is for C16 timber. For C24 timber, the maximum span is 5.12m so if it's built in C24, then the span should be fine. All our joists were C24 as there was basically no price difference.

They also say these are the spans before you get beyond the deemed acceptable 14mm deflection of the floor. I guess if that happens, you start to get cracks in the plaster below.

Based on all of this, it does seem a little unwise to have a load of heavy machinery upstairs (not least think of how hard it will be to get all that equipment up there). However, the idea of it all crashing through the ceiling feels a little dramatic. 

If in doubt, I would speak to a builder or structural engineer.


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## MikeG. (9 Mar 2019)

Peterm1000":2405elvz said:


> .......... I looked in the building regs............



I don't want to split hairs, but there are no longer any span tables in the Approved Documents (BUilding Regs). And I have no idea what table you are looking at, as mine for C24 give a max span of 4.97 at 400 C's.


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## Doug71 (9 Mar 2019)

There must be so many first floors underspeced.

I got a nice freestanding bath for my conversion, when I checked the specifications it was over 300kg when full of water, add a couple of people and you are talking 450kg+.
I made sure the joist would carry it but the builder and building control didn't pick up on it at all yet if I said said I was putting a cast iron table saw up there I'm sure there would have been an issue.


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## MikeG. (10 Mar 2019)

I always double up joists under bath locations, and specify a load-spreader on the floor under the feet to relieve the point load. The thing with baths is that they generally stand fairly close to a wall, and bathrooms are generally small rooms, and thus the span is generally small. That's quite a different thing to standing a piece of equipment in the middle of a floor which was under-specced to start with. Filing cabinets are the other one to watch out for: paper is damned heavy. The only total floor failure I've ever seen was because of a row of filing cabinets.


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## Blackswanwood (10 Mar 2019)

Sounds risky. https://www.ehow.co.uk/how_7485788_calc ... acity.html may help or confuse further! I would want a structural engineer to opine.


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## MikeG. (10 Mar 2019)

Blackswanwood":16hoch5w said:


> ........ https://www.ehow.co.uk/how_7485788_calc ... acity.html may help or confuse further! .........



Confuse, definitely. That again is dealing with a uniformly distributed load, not a point load.


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## dizjasta (10 Mar 2019)

This thread has been interesting and informative, it seems your workshop was erected some time ago and may have been constructed to regulations that prevailed at the time. Is this the case? Present day tables for beam sizes and spans for domestic applications will provide advice for the designer to provide a safe structural member which also avoids cosmetic upset due to deflection that may affect plaster decoration.
I doubt your workshop needs decoration. On the information to hand It seems the first floor was intended for storage at around 40lb/ft2* and allowed pedestrian access for up to 4 people.
I think further examination of the flooring strength is needed. I believe that your floor will take your equipment and 2 people but no storage.
It is estimated that your first floor space has an area of 330ft2* supported by 14 joists that will have full loading with the 2 joists at either end being ignored. What is the first floor size?


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## MikeG. (10 Mar 2019)

dizjasta":3ffwh4qm said:


> This thread has been interesting and informative, it seems your workshop was erected some time ago and may have been constructed to regulations that prevailed at the time. Is this the case? Present day tables for beam sizes and spans for domestic applications will provide advice for the designer to provide a safe structural member which also avoids cosmetic upset due to deflection that may affect plaster decoration.
> I doubt your workshop needs decoration. On the information to hand It seems the first floor was intended for storage at around 40lb/ft2* and allowed pedestrian access for up to 4 people.
> I think further examination of the flooring strength is needed. I believe that your floor will take your equipment and 2 people but no storage.
> It is estimated that your first floor space has an area of 330ft2* supported by 14 joists that will have full loading with the 2 joists at either end being ignored. What is the first floor size?



All of which suggest you too are treated this as a uniform load, not a point load.


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## sammy.se (10 Mar 2019)

What is a cross beam ( I don't know the right term) was placed above and perpendicular to the joists, and the joists then attached to them?

I know it sounds a bit crazy, and introduces a massive trip hazard... But...

I only suggest this because in my Victorian house loft, there is a 3x8 beam across the 2x4 ceiling joists at the mid point, supported by the brick walls, and the joists are attached to it. Presumably to prevent sagging. The total span is about 5 meters.

I know, not ideal, but maybe this might make it possible?

Sent from my Nexus 5X using Tapatalk


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## MikeG. (10 Mar 2019)

Underneath is the obvious answer.


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## sammy.se (10 Mar 2019)

MikeG.":27siw81w said:


> Underneath is the obvious answer.


 

Even better.

OP - why not just add a beam below? 

Sent from my Nexus 5X using Tapatalk


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## dizjasta (10 Mar 2019)

MikeG.":x63bv3op said:


> dizjasta":x63bv3op said:
> 
> 
> > This thread has been interesting and informative, it seems your workshop was erected some time ago and may have been constructed to regulations that prevailed at the time. Is this the case? Present day tables for beam sizes and spans for domestic applications will provide advice for the designer to provide a safe structural member which also avoids cosmetic upset due to deflection that may affect plaster decoration.
> ...


Mike my comments are directed to the original poster to garner information. No mention of "uniform load".


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## dizjasta (10 Mar 2019)

dizjasta":1e7f5d3s said:


> This thread has been interesting and informative, it seems your workshop was erected some time ago and may have been constructed to regulations that prevailed at the time. Is this the case? Present day tables for beam sizes and spans for domestic applications will provide advice for the designer to provide a safe structural member which also avoids cosmetic upset due to deflection that may affect plaster decoration.
> I doubt your workshop needs decoration. On the information to hand It seems the first floor was intended for storage at around 40lb/ft2* and allowed pedestrian access for up to 4 people.
> I think further examination of the flooring strength is needed. I believe that your floor will take your equipment and 2 people but no storage.
> It is estimated that your first floor space has an area of 330ft2* supported by 14 joists that will have full loading with the 2 joists at either end being ignored. What is the first floor size?


NickM do you have any details to hand so this matter can proceed or perhaps DEVELOPE!!!!!!!


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## deema (10 Mar 2019)

I would listen very carefully to Mike. An architects opinion on such things is not something I would ignore.

The old rule of thumb for floor joists was to half the span and for every foot use 1” of thickness plus an inch. Interestingly your joists should only have been used to span 14’ using this rule. 

As a slight aside, I understand building regs were first started in 1965. I’d appreciate knowing from Mike if modern regulations apply to old floors built before this time or do they have grandfather rights?


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## NickM (10 Mar 2019)

Unfortunately I don’t think a beam underneath is possible (or at least would be too big a job).

I wanted to use the space above the garage, because I thought it would be fun to embark on a new hobby making sawdust upstairs, whilst carrying on with one of my other pastimes of tinkering with a car I built a few years ago downstairs.

However, taking account of the helpful comments here, I think I am going to move to plan B which is to set up ‘shop in an old stable building. There is some negotiating to be done as I may need to turf out some of my wife’s bee keeping kit and some camping gear, but that’s all light so should be safe above the garage. In reality, I think the stable will actually be a better space. For a start it’s full height and it’s on the ground! I’m fortunate to have an alternative. 

So, I’ve got a few things to organise, but I think I can start looking around for some machines again!

Thanks again.


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## MikeG. (10 Mar 2019)

Now you're talking! Let's see a photo or two of this old stable..........


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## MikeG. (10 Mar 2019)

deema":2zyfpi33 said:


> The old rule of thumb for floor joists was to half the span and for every foot use 1” of thickness plus an inch. Interestingly your joists should only have been used to span 14’ using this rule.



Plus 2", and you never go far wrong. That rule only applies to 2" wide joists, though, and his are 3".



> As a slight aside, I understand building regs were first started in 1965. I’d appreciate knowing from Mike if modern regulations apply to old floors built before this time or do they have grandfather rights?



Building regs only apply to stuff to which new works are done. Old stuff benefits from the principle of "at least as good as it was before" if it is rebuilt/fixed up but falls below the threshold of being controllable. So, as long as no work is done to old floors, building regs are irrelevant (unless stipulated by, say, an insurance company or a mortgage provider).


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## NickM (11 Mar 2019)

MikeG.":xw2063h4 said:


> Now you're talking! Let's see a photo or two of this old stable..........



I’ll try to do that!

The garage has a bit of history. I think back in the day it would have housed a proper vintage car (would have been state of the art then of course). It used to have a pair of sliding doors - the tracks are visible in the floor. There’s even an old petrol pump and, I assume, there must be a tank underground somewhere.

Unfortunately a beech tree fell on it about 15-20 years ago and pretty much destroyed it. The previous owner of the house was in the garage with his son when it came down - the tree was already listing severely and they were trying to rescue his Triumph TR6! It was probably the heavy cast iron petrol pump which saved them as it stopped the tree getting right down to floor level. They rebuilt it and took the chance to add the upstairs room.


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## deema (11 Mar 2019)

Thanks Mike, really appreciate it.


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## NickM (11 Mar 2019)

Partly as a test to see if I can upload photos, here is a shot of the stables in the snow. The stables are either side of the stable door - you can only see one side (with the arched window).


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## NickM (11 Mar 2019)

The picture upload worked!

Here is a picture of the inside of one of the stables with the current “horse” - my dad’s old Wrigley truck which spent a good twenty years in daily use in his greenhouses in Guernsey before he retired from growing flowers. It now gets a bit of use shifting stuff around my garden (when I can get it to start...).

The stables are smaller than ideal but I think I’ll start in one side and gradually move into the other as I subtly move my wife’s bee keeping stuff out...

The “chocolate bar” floor is going to be a bit of a challenge in terms of getting machines/benches level, but I’ll find a way to overcome that.


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## MikeG. (11 Mar 2019)

Brilliant. That should make a wonderful workshop. Get some more photos when you can, and we'll see the size of the task. It might be worth leveling the floor before moving anything into there.


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## NickM (11 Mar 2019)

And finally, here’s a picture of the petrol pump in the garage which I mentioned in a previous post (sorry, it’s on its side).


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## Bm101 (12 Mar 2019)

If I had spare unused brick built stables with concrete floors I would also have chosen to ignore them and install heavy machinery in my actual house. On the second floor. 

 

No offence meant Nick in _any_ way. I'm sure there's a multitude of reasons .


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## Bm101 (12 Mar 2019)




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## NickM (12 Mar 2019)

Bm101":fy4ch3tu said:


> I'm sure there's a multitude of reasons .



Yes. The main one was the fact that my wife’s stuff currently occupies the stables!


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