Building a floor, joists and bearers... one for the joiners

[grim_d]

Good Evening,

I have just this evening been given the key to my new unit and would like to get a floor up for storage etc before getting the car in.

Before I go to my local builders merchant and my jaw hits the floor at the price of timber I would like to know if I am on the right track in regards to joists and bearers etc.

See below for my highly technical drawing on the subject, if constructed out of 2 x 8 will it be strong enough not to randomly collapse? is 3m between the bearers too much?, if I added a bearer in the middle of each and brought it down to 1.5m would this be better?

Red = Bearer
Green = Joists between bearers
Black = Joists



Thanks in advance and any more info required let me know!

Edited by grim_d on Friday 2nd July 23:58

[DrDeAtH]

just add 2 noggins per joist span (1 per metre) to give the flooe some strength. you may find 400mm centers better as the flooring you buy will be 600 or 1200mm wide. just remember to stager the joints and use 2"x 10 (5.0 x 50) screws

[herbialfa]

Do a Google on Joist span tables!

You'll get what you need to know from there!

[Spudler]

Ditto the above posts.
Also bear in mind , if using ply for flooring, some will come in 2440 lengths so decide what type of flooring you'll be using before setting out the joists. As mentioned above 400 centers is the norm.

[grim_d]

I thought I would have got away with 450mm centres but I will reduce to 400mm if recommended.

I did search for span tables but they don't seem to mention the spacing between bearers which is really my main concern, any ideas?

[Busamav]

grim_d said:

I thought I would have got away with 450mm centres but I will reduce to 400mm if recommended.

You would be fine with 450 ctrs , but as they guys above mention , you will be cutting the flooring and there will be lots of waste , 400 is the norm.

[TimCrighton]

The distance between the barers is all going to be down to the loadings that are going to subject the floor too. Remember also that your work will be subjec to Building Regs so I would suggest double checking at www.planningportal.gov.uk the requirements that you will to include. Handrails etc will be necessary. Most mezzanine flooring for storage is 50mm so that may be special order for a builders merchants but that is with metal joists and frame work.

[benmc]

Just looked at my loading tables

For a 4m span you are looking at the following

Dead load (kN/m2) excluding self-weight of joist - More than 0.25 but not more
than 0.50

450mm between joists

44*220
or
47*220

It would be the bearers that concern me. What are they supported on?

Ben

[grim_d]

Not sure what that means in laymans terms? I'm a bit rubbish at physics.

The bearers will be supported on a concrete floor with brackets and tethered where possible to the structure of the building.

[benmc]

I am no way a professional but have done some selfbuilding with joists etc etc

My concern is the green lines. They are supporting quite a load as the take the load from each of the beams at right angles.

grim_d said:

Not sure what that means in laymans terms? I'm a bit rubbish at physics.

The bearers will be supported on a concrete floor with brackets and tethered where possible to the structure of the building.

[grim_d]

That was one of my concerns also, I'm willing to add more bearers if that is what is required?

Like the below?

[grim_d]

Well thanks for the replies guys but the chap who owns the building has donated some I-Beams and joists to us and is even going to erect the floor for us.

Which is nice.