Piano World Home Page Forums Our Most Popular Forums Piano Forum OK so a 700 pound grand piano walks into my house and...

If the problem were point loads, tip-toeing would be the wrong thing to do. You should walk as flat-footed as possible. Better yet, just stand still!

Update: A carpenter spent 4 hours today installing the 2 by 10 blocking between the floor joists where the Piano legs sit on the floor. The blocking was then cross-braced between the three joists.

Next week a double 2 by 12 beam will be installed across the middle of the room with a steel post to the concrete base.

Pics will follow when the whole thing is done...

My first house was a wood house, up off the ground. Built in the forties. I didn't have a piano at the time, but I did have a six foot long marble pedestal table. The pedestal was about 15x24 or so.

I was worried about it, but the table actually made things more stable. Previously, things would rattle when I walked around but after I brought it in, all that stopped. It was still more rattle-ish than a slab, but not by much.

Is this over a crawl space or a full basement?

Fully insulated 5 foot high crawlspace.

"Fully insulated 5 foot high crawlspace." That is good news. It means you can probably support the joists nicely with the 2x12s. How many feet do the joists span? And what is the dimension in the other direction perpendicular to the joists? Finally, are the joists 2x8 or 2x10's.

The joists in my 110 year old house are 2x8's and span 16 ft (the 2x8s are actually 2 inches thick). When I moved in I did not notice much give in the floor but I hate to feel the floor move in any way when I walk across it so I effectively halved the span by adding my own beams.

I built up beams from three 2x4s side by side. I glued them and also bolted them together to make a solid 4 1/2 (w) by 3 1/2 (h) beam that was 8 ft long. I supported each beam by two metal cellar posts from Home Depot. I put the beams under (and perpendicular to) the joists throughout the basement. My only costs were the 2x4s and the cellar posts.

This was way before I bought the Knabe grand. The addition of the piano had no noticeable effect. I also put steel plates under the piano feet so as to distribute the force over a larger area and decrease the localized floor pressure (floor pressure is pounds force per square foot).

So, it sounds like your addition of the 2x12s will effectively cut the span in half and solve the problem. Good luck.

Half the span means a quarter of the deflection -- or even better in this case, as you're making the joists into continuous beams. Adding a girder and some piers and posts should do the trick for the OP.

A quarter of the deflection would be just fine.

I noticed last night that even though only a part of the support system is in place, the floor movement is already down by a third in my estimation. The entire 25 square foot floor system directly under the piano is now one continuous support structure.

Once the vertical support is added we should be in great shape.

Final supports were put into place today. Most of the vibrations are gone. Very happy with the results.

Pics of the final supports below:

You have improved the spec. of your house by doing all that.

hey Brian,

Tell you contractor good job for me, will you? Very smart approach to his blocking technique. He's managed to spread the PSI around with that configuration. I take it he prepped the soil below the pier anchors, how did he do that? I question that because I've got to do the same thing with a portion of our back deck. The cement piers worked great but the soil still let go so it's round 2, except this time, I'm doing it myself!

Thanks in advance...........blob

Hey blob;

I'll pass the good word on. The soil below was compacted sand to begin with, over hard clay. They compacted the base a bit more and then laid the foundation blocks.

One other thing they did after my pics. They laid a double 2x6 between the two main piers, right up against the three trusses that the piano spans. That provided additional support right across where we walk into our office.

The end result? About 90% of the movement is gone. The top of the piano lamp barely moves now. Perhaps an extreme measure, but seems to have worked as designed.

I have an SDS-Max Boschhammer with the 5" x 5" tamping attachment that I've used to prep the hole for placing concrete piers. Measure the space you'll be working in, and rent the biggest one that'll fit.

Or, the low budget high exercise approach is to do the same sort of compaction, only using a hand sledge to beat on a scrap of 4x4.

Brian and John,

Thanks for the info guys. I'll put those procedures to use when I start that project. thanks again.........blob