Floor Strength Question

[Bill Grumbine]

Greetings all

The time has come to go shopping for a new bed, and SWMBO and I were out looking at the possibilities. We are both interested in a water bed of a particluar design. I do not really feel like typing out history of bed types, reasoning behind it, etc, since I want to keep this short and to the point. Translated, that means I don't really want to hear about different beds I should be considering. I want to know about how to calculate loads and load bearing capacity before we make a decision.

What I need to know is how to calculate the ability of our floor to bear the load of this particular bed. The total weight is going to be just under 1000 lbs. The floor is in an old stone farmhouse, and consists of old pine boards approximately 7/8" thick. The joists are set on 24" centers, and are mixed fir and chestnut, approximately 2 1/2" x 7 3/4". The main beam is red oak, 7 1/2" x 10". The joists are mortised into the main beam at the center of the house, and set on a stone sill on the outer wall.

If I had to make a guess I would say the floor would support the weight, but I would feel a little better with some objective figures. Having written that, if anyone here has the formula for figuring this stuff out, I would appreciate hearing about how to do it.

Thanks.

Bill

[Chuck Wintle]

I guess if you could always double up on the floor joists to be safe. One detail you left out is the joist span.

[Bill Grumbine]

Yeah, I forgot that measurement Charles. The span is just a hair under 12'. I've got this question going on another forum as well, and while things are a little hazy from an engineering point of view, we had a waterbed in our last house for almost 14 years with no problems. The bed weighed over twice as much and the room size was pretty close to the same, so I am thinking I will be fine with it.

Bill

[Jim Becker]

I know you didn't want to hear it, Bill, but honestly, water beds are not the best for larger people. I had one years ago and found it got less comfortable over time as I, um...expanded. I've heard the same from others. Frankly, the Select Comfort we have now (dual zone) is the most comfortable bed I've slept in consistently, particularly because Dr. SWMBO and I prefer different firmness...she very soft and me mid-range. It has even support like you get with a water matress due to the pneumatic nature of the system without the excessive weight that a water matress brings, too.

[Ben Grunow]

The only help I can offer is to suggest some thins steel plates to spread the load or a 2x6 spanning the bed feet (if bed skirt will hide one) across the joists. Examining hand hewn timbers is a sketchy endeavour given their varying sizes and different wood types/age and one good knot will throw the whole thing off (modern lumber is sawn around large knots and graded for different uses based on knot sizes and locations). Sounds to me like your floor will be fine if a little bouncy.

I would get a couple more people and stand in the middle of the room and bounce a little and see what happens. Sounds unscientific but it will tell you what the room wil be like with all that weight in it. The floor will hold it but it might be sagged and bouncy. If it is marginal, get one of the sleep number beds that Jim and I have and you wont be disappointed. The other great thing about them is that they are very light weight (makes moving them a snap). I am 250 and it has held me up for 4 years with little sign of wear. Sorry to advertise to you (no affiliation-just happy customer).

Good luck.

[Bill Grumbine]

Ben (and Jim), we've had an air bed for seven years now, and it has seen better days. We had a waterbed before that for 14 years, and decided to go back. I did a fair amount of studying today, and it looks like we are in good shape for what we want to do.

Bill

[Charles McKinley]

Hi Bill,

Has there been any "modification" from past plumbers or eletricians that may have notched any of the joist? Is there an easy way to check all of them?

[Joe Pelonio]

Bill,

We were waterbed owners back in the '70s, remember the old fashioned
ones, one big bag of water? Ah, those days. When we first moved here we had the kind that looks like a normal queen sized bed but the matress unzips to reveal a water bladder with several "tubes" for less lateral movement. Since it's upstairs I was a little nervous but with some investigation discovered that the center of the bed was placed over the main 4x12 beam, and with 3/4 plywood subfloor figured it would be fine and it was.

In your case I'd definitely take a close look, and make sure ahead of time.
The size of the wood on yours sounds fine to me but make sure it's all secured.

[Bill Grumbine]

Hi Bill,

Has there been any "modification" from past plumbers or eletricians that may have notched any of the joist? Is there an easy way to check all of them?

Hi Charles

There is one pipe to the radiator where the joists for part of the room were notched, but they were covered over with some steel that is nailed down on both sides over the notch. There are probably three holes of 3/4" diameter, one in each of three joists. I have not gotten a definitive answer through math, and it does not look like I am going to get one, but thinking about the amount of people who have been in the house in various rooms all at one time, I am confident that there is not going to be any catastrophic failure. I don't remember if you remember looking up at the joists when you were here, but they are stout and clear. People back then knew a lot about how to build with wood, perhaps more than a lot of us do today. At least, those who built houses that have lasted as long as ours has knew a lot. ;)


Bill,

We were waterbed owners back in the '70s, remember the old fashioned
ones, one big bag of water? Ah, those days.

Joe, we had one of those for 14 years. It was great, but we are a little older now, and a little more sedate. Notice, I did not write sedated! But the tube style looks like a real nice alternative.

Bill