# Workshop floor joists



## Ram64 (20 Jan 2019)

HI all,
I'll be starting a new workshop build soon (hammer) , just a 10 foot by 8 foot affair and have a question about floor joists.
I've recently acquired a number of lengths of reclaimed 5" x 4" (150mm x 125mm actual) at 10 foot in length. Is it reasonable to assume these will make an 8 foot span unsupported? The nearest size by comparison in any span table is C16 150mm x 47mm which at 600mm centres is showing a max span of 2.76m. Does the extra width make any gains?
Thanks in advance 
Nigel


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## woodbloke66 (20 Jan 2019)

MikeG is your top bloke for this but I'd hazard a guess and say 'no'; you're going to need some sort of support mid way - Rob


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## J-G (20 Jan 2019)

Ram64":3iw3p6ca said:


> HI all,
> I'll be starting a new workshop build soon , just a 10 foot by 8 foot affair and have a question about floor joists.
> I've recently acquired a number of lengths of reclaimed 5" x 4" (150mm x 125mm actual) at 10 foot in length. Is it reasonable to assume these will make an 8 foot span unsupported? The nearest size by comparison in any span table is C16 150mm x 47mm which at 600mm centres is showing a max span of 2.76m. Does the extra width make any gains?



Since 2.76m is just over 9 feet, whether there is any gain by using joists 2.6 x wider than that quoted in the table is irrelevant. Of course there will be gains but finding out how much would be a futile exercise. A rough calculation suggests those beams could span 5m .

Incidentally 150 x 125 is ~ 6" x 5" not 5" x 4"


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## deema (20 Jan 2019)

Mike G is the expert. 
The old carpenters rule was half the span plus an inch for floor joists (4” +1”I.e. 5”), so i will be interested to see what Mike has to say.


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## MikeG. (20 Jan 2019)

Ram64":cumce8hu said:


> ........ 5" x 4" (150mm x 125mm actual)........



Which is it?

Given that 150x125 is not a standard size, and something I've never come across in softwood, I'm guessing you meant 125x100.


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## Ram64 (20 Jan 2019)

125 x 100 it is........apologies


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## Ram64 (24 Jan 2019)

I even looked at the wrong dimensions in the tables. Gawd that was a bad, must try harder (homer) 

Looks like the nearest equivalent is 75 x 122, which at 600 mm centres is between 2.34m and 2.73m depending on the loading. Once again apologies for the confusion.

Thanks again Nigel


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## screwpainting (13 Feb 2019)

I've recently acquired a number of lengths of reclaimed 5" x 4" (150mm x 125mm actual) at 10 foot in length. [/quote said:


> Whatever you do, treat those reclaimed timbers and particularly, trim, check and drench the end grain with a good rot treatment.
> Much better to be safe than sorry.


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