hello,
i need to increase the head height in my basement by about 3-4″ for an area about 3’x3′. this is to allow adequate height for a piece of equipment.
my joists are 2×8’s, 16″ on center. i’ve thought of two possible scenarios.
1) cut out 3′ of a joist, head it off at either end and insert doubled up 2×4’s in place of the old 2×8″, or maybe use a scrap of 4×4 paralam
2) cut out 3 to 4″ of a joist (basically notch out 3′ of it), and sister/glue plywood on either side
would either of these be adequate?
i have diagonal subfloor (3/4″ roughsawn) on the joists and 3/4″ oak flooring above that.
thanks as always,
john
Replies
boxing joists
That doesn't seem to be too large an opening, I would cut it out and us doubled 2x8s around the opening, if you have reasonable flooring above and you don't plan to put something extremely heavy on it, it should be find.
Doubled 2X4s won't work.
The doubled 2X4s are not structurally equivalent to a 2X8.
You could probably sandwich the existing 2X8 between two pieces of 3-inch by 0.020 angle iron and run them three or four feet past the area you want to raise, and then trim off the bottom.
YOu should really get an engineer involved. It will cost a couple of hundred dollars, but you will get a real answer, that doesn't involve the floor sagging over time.
Need to know more to begin to give an adequate answer, but your proposed sounds poor.
When making a hole, which is essentially what you are doing, you must first double or triple the adjacent joists, then attach your header to them properly.
How long are your 2x8s?
What loads come to bear on them above?
are you able to take up any load with posts?
I was faced with a similar once and hired an engineer. This was 2x12 spanning 12'6" at 16" oc
we reframed with double 2x6 @ 12" oc
thanks everybody. i appreciate the input.......fortunately i have an engineer friend i could run this past. i apologize, i suppose i knew this instinctually, but wondered if i was overthinking. i guess its never a bad idea to get a pro involved
again, thank you
How about
going down instead of up?
By that I mean, it might be easier to open the (basement slab?) and go down a few inches, if that would be suitable for your application, than modifying a marginally constructed floor.
I was just going to say that. Cutting out a 3'x3' square of slab floor, digging down another 4"-8", then re-pouring a new minislab with forms to match up to the new height.
You would need to come up with an easy way to drain it if you had a basement flood.
Now paul
There is no EASY way to drain a basement flood