This length has a maximum safety capacity that is based on the width and material used to make the floor.
Floor bent over joist.
By building a wall under joists you divide the span.
It is interesting to note that the deflection of the subfloor and underlayment panels in figure 1 relative to the top of the joist is zero no deflection even though the panels are clearly bent over the joists as represented by two radii r and 1 44r.
The longer the distance a joist spans without support the more it will flex.
I am wanting to install real hardwood flooring over my wood sub floor.
I live in south east texas it gets hot here so a c runs a lot.
On the top side of the floor another fix it idea to lay down new hardwood over the existing floor.
But it s usually best to run the sister joist over the entire span.
What i have for a sub floor is 1 2 plywood then 15lb felt then 5 8 plywood.
While most residential construction uses 2x8 joists with 16 inch spacing there are many other factors you need to consider when determining the proper joist span length.
When the sagging joists are level apply a generous bead of construction adhesive to the existing joist.
Then attach the sister joist using three 16d common nails driven every 16 in.
A plywood subfloor will bridge any minor waves in the existing floor and leveling compound would help too.
Joist span and spacing is set by your local building code.
You will have to make sure your joists can handle the addition of considerably more weight from the plywood subfloor and any floor coverings.
If you build a wall to support joists be sure to place a stud directly and tightly under each joist.
But larger is not always better when builders are constructing a home or adding a room addition.
Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor.
Driving 16d common nails in old hard wood is difficult.
There shouldn t be any cuts or penetrations in the middle third of the joist or at the bottom of the joist either.
However the amount of bend or deflection allowed by most building codes typically joist length divided by 360 does not address the nature of lumber to creep creep in this sense means to nominally bend over a prolonged period of time.
As an organic material wood joists are prone to deflection under load.
I also have 6 bat insulation on bottom being held up with chicken wire.
When building a house or even a deck it is important to confirm you have the correct joist sizes spans and spacing before you get started.
The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example.
The floor above will be stiffest if you place the wall in the middle of the joists.
