I would consider trying to spread out the load, but I've thought about whether plywood screwed into all the joists is a better option. I built a kitchen island with a granite countertop placed in a similar way directly over a truss. I calculated it and concluded that the weight isn't more than what you have there, but even more spread out, since I used skirting instead of legs.
It all went great, but after a few months I started noticing paint flakes on the floor in the room below. It turned out that the ceiling was starting to sag due to the prolonged weight... My solution (after quickly jacking up the ceiling temporarily) was to install a laminated beam in the ceiling to keep the kitchen island in place.
But, note that this is in a house from '74 that was built in an afternoon when all the inspectors were on break and the frame consists of fast-growing balsa wood, and the builders involved were heavily alcoholic. (Perhaps I'm exaggerating a bit, they probably had a sober apprentice.)
It all went great, but after a few months I started noticing paint flakes on the floor in the room below. It turned out that the ceiling was starting to sag due to the prolonged weight... My solution (after quickly jacking up the ceiling temporarily) was to install a laminated beam in the ceiling to keep the kitchen island in place.
But, note that this is in a house from '74 that was built in an afternoon when all the inspectors were on break and the frame consists of fast-growing balsa wood, and the builders involved were heavily alcoholic. (Perhaps I'm exaggerating a bit, they probably had a sober apprentice.)
Okay! Then you also had better conditions than me since you have pedestals. Our house is also built in '74...Dowser4711 said:
Do you know if you also had 220mm beams? What was your longest distance to a load-bearing wall? Did you insert "glulam pieces" between the roof trusses or did you install a completely new beam?
A 20mm plywood is the simplest solution that might be sufficient...
Yep, 220mm beams with a 3.5m span, so it *should* have worked.
I simply inserted, no wait, I inserted two glulam beams, (because the 220 beam I got hold of happened to be around 8m, and it felt unnecessary to throw away half rather than being needed)
parallel to the existing center beam after I jacked up the beam with a hydraulic jack.
Then I used several French wood screws to pull all three beams together into one unit since the floor is only attached to the original beam.
(I didn't want to deal with any kind of moving gap between the floor and the glulam that could make noise when walking on the upper floor.)
If I had opened up from the upper floor, I probably would have placed the beams in the middle of the existing ones and screwed the floor to them.
I simply inserted, no wait, I inserted two glulam beams, (because the 220 beam I got hold of happened to be around 8m, and it felt unnecessary to throw away half rather than being needed)
parallel to the existing center beam after I jacked up the beam with a hydraulic jack.
Then I used several French wood screws to pull all three beams together into one unit since the floor is only attached to the original beam.
(I didn't want to deal with any kind of moving gap between the floor and the glulam that could make noise when walking on the upper floor.)
If I had opened up from the upper floor, I probably would have placed the beams in the middle of the existing ones and screwed the floor to them.