Support beam for springy floor. Calling all Google School O' Engineering Grads

[Malcolm Schweizer]

But seriously- calling upon the collective knowledge of the forum. This isn't a real difficult problem to solve.

The house is 180 years old. The floor joists are pitch pine and floors are heart pine. The joists are 3x6 spaced 2' on center. I'm amazed that they have held up as well as they have. The rooms upstairs are all fairly short spans except the living room, which spans 15'6"x17'6". The room below that is 15'6"x14'6", so there is a stone wall resting under part of that upstairs span.

All I want to do is build a laminated beam 12"x6"x15'6" and run it down the middle of the joists to divide the load and stiffen up that upstairs floor. The ceiling is plywood wainscoting trimmed with crown moulding. I really don't want to pull all that down. My thought is to build a bracket to support the beam and have it galvanized and powder coated. Use a trim saw to trim out only the wainscoting where the beam goes, trim away the crown moulding, and set the beam, then trim it out with a small piece of moulding to cover any gap along the ceiling.

Any objections? The walls on either end of the beam are 16" thick stone masonry construction, and the support would be lag bolted into that. I really do not want a support post because it interferes with furniture placement. Do the joists need to be mechanically tied to the beam, or can they just rest on the beam?

The floor is only sagging a tiny bit, and it's not terribly springy, but certainly it could be more stiff. So I guess I'm saying this doesn't really need to support a lot of load- just help out what is already there.

Crude sketch- bracket would be designed a bit more decorative than this, with decorative ends like these http://www.leevalley.com/US/wood/page.aspx?p=73947&cat=1,71685,73945


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[Malcolm Schweizer]

Bracket would also extend much further into the beam and made from 1/4" steel plate.

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[Lee Schierer]

Without knowing what is inside the wall where you intend to anchor the bracket, you may not gain anything. Beams should transfer the load to the foundation via columns. Obviously, 3 x 6 joists spanning 14 feet on 24" centers is not adequate. Your photo appears to show a door or window below where you plan to anchor your beam, which would not be structured to pick up the weight load. A good contractor or structural engineer on site could give you a better qualified opinion of what is needed and what size beam would work to stiffen your floor.

[Malcolm McLeod]

... The walls on either end of the beam are 16" thick stone masonry construction, and the support would be lag bolted into that.
Just to verify, the new beam is perpendicular to the joists above?

Any chance you could cut pockets into the interior stone wall to receive the ends of the new beam? This might also require a pass-thru hole/pocket in the opposite wall so the beam could be slid into place. ...Maybe? Or, cut one pocket deep enough to allow the beam to 'over-insert' and then slide part-way out when the opposite end is in position (not sure how to say this better). With the beam solidly supported on the stone walls, the brackets become optional. This would be more work, but last forever.

You might also consider a new LVL structural beam, placed as you outline, properly supported (method TBD), with a half inch or so between it's top and the beaded ceiling. You could then insert wedges at each joist to ensure uniform load distribution. Then 'wrap' the beam with the finish wood of choice.

Food for thought...

[John K Jordan]

Malcolm,

Interesting problem! How did you size the beam? When I built one to hold up a new roof section an architect friend put me in touch with a structural engineer who sized the beam for me.

My house is timber frame with exposed posts and beams everywhere. Just looking now, I see a 6"x12" solid pine beam on a 15' span supporting part of an upper room. An 18' span is a 8"x12" beam with a support post on either end.

Another option might be to weld end brackets on a steel I-beam and box it in with wood - might result in a smaller beam if that would be desirable. The box could even hide the end brackets and bolts. A friend of mine used huge solid posts and beams in his house. All these are old timbers dredged from Lake Superior except he was short one post. To disguise the difference, we resawed a 12' board into 4 thin pieces to skin the odd post.

I assume by no posts you mean at the ends of the beams as well. All of the beams in this house are supported by posts on the ends. I suspect the brackets would work if the masonry is sound but I don't know how to check that. Another possible option would be to hide steel supports poles in the masonry walls but that would be a big project.

Also, if you use exposed brackets a blacksmith might be able to make steel brackets that don't look like they were made today, or at perhaps modify a new perfectly smooth modern-looking steel bracket with a hammer to make it look 100 years old.

JKJ

[Malcolm Schweizer]

That is actually an armoir below the beam- not a door. The wall is granite stone and mortar construction. It is plenty strong to support the beam. It falls on a "T" where there is another wall behind that one. On the opposite end of the room is an exterior wall 16" thick stone construction.

The size of beam was calculated based on span and load plus a huge fudge factor.

I really don't want a support post, and no way am I chipping into the wall- way too challenging. I would do a post before I did that. I will run it by an architect but trying to rough out what I can do before I send it to her for review.

Keep in mind that the floors and joists are original to the house and still holding well, and I am only trying to eliminate some of the springiness to the floor above and am not reengineering the whole floor. This just will go under the existing joists.

[Adam Herman]

the only problem i see is your potential connection to the masonry. old mortar will not hold anything in tension as your bolts will be. Masonry is really only strong in compression. You need to create a pocket in the walls to do this permanently. The beam could end at the surface of the wall if your steel bracket extended back into the wall some distance to transfer the load directly to the wall, and not through bolts. use a demo saw to cut slots for the steel plates.

[Michael Dye]

Another suggestion. How about building a less decorative bracket for the ends. Construct a series of exposed beams that would rest under the existing beams, then finish the entire group as exposed beams, including a veneered surface and decorative end caps. Looks to me like the attachment to the existing walls would put the bolts in shear, not tension. Something to think about. Good luck

[Malcolm Schweizer]

The backup plan is a series of smaller joists. It seems to me either way it's really a large or small version of this:
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Doing some research and I found a few examples where they used a narrow support post on each end bolted into the wall. I may be able to tolerate that. I really wanted to keep the furniture flush against the wall without a post being in the way. If I can get by with a 3" thick support post I might live with that. My one concern is as mentioned above- I would be depending on the lag bolt shear strength to support the load.

[Malcolm Schweizer]

My neighbor's house. Notice the iron "shelf supports" bolted to the wall and holding the porch. (By the way, interesting note- this was the former home of General Santa Anna who led the Mexican army in the Alamo.) This suggests to me that the walls (same stone construction) could take the bolt-on idea.
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Appreciate the replies so far. Once I draw up a plan this will go to an architect friend for approval. I'm just trying to keep it to "Here- finesse this and approve it" and not "Charge me an arm and a leg to totally redesign this."

[Karl Andersson]

Hi Malcom,
I've seen balcony construction like Santa Anna's while working rebuild jobs in New Orleans; those brackets are often just bolt-on decorations, not structural and the balcony sits on structural iron/ steel beams that are cantilevered out from inside the house structure, so it may not be what it seems. Sometimes the decks sit on a metal ledger that runs along the wall under them with long bolts completely through the masonry wall, anchored by star-shaped or round "washers", but then they have columns down to the street for vertical support.

I just made and installed a laminated 6"x12"x24'stiffener beam for a room with a crawlspace under it so my wife can do her aerobics without the knickknacks falling off the shelves, etc. I put in two support columns along the spans, but I think your idea will be fine to strengthen your floor since the house has held up so long. It's likely your old beams are a lot better/ stronger wood that modern BORG Hem-Fir crap.

I wouldn't use lags like you've shown unless I had an engineer tell me the bolts and anchors I had were up to the shear forces - your beam won't be as heavy as mine, but you still don't want it falling on you. If you can't find hardware to do what you want, how about a 2x6 "column" from the floor to the beam at each end, lagged/ anchored into the wall with corbels or brackets at the top to widen the bearing surface? 2 inches from the wall isn't much for furniture to hide.

Karl

[Malcolm Schweizer]

Hi Malcom,
I've seen balcony construction like Santa Anna's while working rebuild jobs in New Orleans; those brackets are often just bolt-on decorations, not structural and the balcony sits on structural iron/ steel beams that are cantilevered out from inside the house structure, so it may not be what it seems. Sometimes the decks sit on a metal ledger that runs along the wall under them with long bolts completely through the masonry wall, anchored by star-shaped or round "washers", but then they have columns down to the street for vertical support.

I just made and installed a laminated 6"x12"x24'stiffener beam for a room with a crawlspace under it so my wife can do her aerobics without the knickknacks falling off the shelves, etc. I put in two support columns along the spans, but I think your idea will be fine to strengthen your floor since the house has held up so long. It's likely your old beams are a lot better/ stronger wood that modern BORG Hem-Fir crap.

I wouldn't use lags like you've shown unless I had an engineer tell me the bolts and anchors I had were up to the shear forces - your beam won't be as heavy as mine, but you still don't want it falling on you. If you can't find hardware to do what you want, how about a 2x6 "column" from the floor to the beam at each end, lagged/ anchored into the wall with corbels or brackets at the top to widen the bearing surface? 2 inches from the wall isn't much for furniture to hide.

Karl

Good day Karl,

Thanks for the reply. If I do a post it would be as you said- a column bolted to the wall and resting on a poured concrete pad. I just don't want the furniture to have to go around the column. I may build a false wall out the thickness of the column and then the furniture is flush to the wall. I'm going to also ask about using a 2" deep column. Seems awful shallow, and not much to mortise into for corbels.

[Malcolm Schweizer]

Update: The joists in the large room are bigger than in the smaller room- 7"x6", and are 22" OC. That's better. Also I didn't think about the fact that they are let in to a ridge beam all the way around, and that ridge beam is more than ample for screwing a hanger into, and then the rest of the hanger can have lag bolts into the stone walls. I believe we have a winner here. (Not drawn to scale.)

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[Charlie Velasquez]

Update:... Also I didn't think about the fact that they are let in to a ridge beam all the way around, and that ridge beam is more than ample for screwing a hanger into, and then the rest of the hanger can have lag bolts into the stone walls. .Just curious, how is the ledger beam supported?

[Malcolm Schweizer]

Just curious, how is the ledger beam supported?

It sits atop a stone wall on one side of the room, and it is let into the stone wall on the other side. (the far side is an outer wall and this is the bottom floor, so it is let into that wall. The other side of the room there is a wall just for the downstairs and it rests on top of that wall.

[Jim Becker]

the only problem i see is your potential connection to the masonry. old mortar will not hold anything in tension as your bolts will be. Masonry is really only strong in compression. You need to create a pocket in the walls to do this permanently. The beam could end at the surface of the wall if your steel bracket extended back into the wall some distance to transfer the load directly to the wall, and not through bolts. use a demo saw to cut slots for the steel plates.
This. The pockets are necessary so you have something to rest the beam on. Surface mounting with brackets is fine for cosmetic things, but not for load bearing. One of the pockets needs to be created deeper and taller so you can slide the beam in that side first far enough to lift the other end up and get it into the pocket on that side. Due to the clearances required to move things back and forth, you'll likely need some shimming on top of the beam after that to engage the floor above it securely.

[Malcolm Schweizer]

This. The pockets are necessary so you have something to rest the beam on. Surface mounting with brackets is fine for cosmetic things, but not for load bearing. One of the pockets needs to be created deeper and taller so you can slide the beam in that side first far enough to lift the other end up and get it into the pocket on that side. Due to the clearances required to move things back and forth, you'll likely need some shimming on top of the beam after that to engage the floor above it securely.

They make beam hangers for timber framing.

[Jim Becker]

They make beam hangers for timber framing.

True. I guess I shouldn't have been quite so absolute in my statement, although I believe that most timber framing beams have tenons into mortises to transfer weight into the post directly.

[Bruce Wrenn]

Go into upstairs room, and pull a tight line across floor. I'm willing to bet sag is worse in middle of the room. We often go under houses, and put up a perpendicular built up beam supported by joist hangers nailed to the existing joists. No posts. This forces joists to share the load, and move as a unit.

[Jim Becker]

Bruce brings up an important thing...to install that beam without gaps, you may want/need to temporarily jack the ceiling "level"...

[Malcolm Schweizer]

Bruce brings up an important thing...to install that beam without gaps, you may want/need to temporarily jack the ceiling "level"...

Yes, my plan is to jack the beam into place and have a person checking upstairs for level. Once in place and the floor is as level as it can be, slide the collar in place, drill holes, and install.

That's the plan. Lots of finger crossing involved.