100+ year old residential timber analysis & reinforcement 2

[RattlinBog]

I'm hoping to get some advice and a sanity check on a few things. In my spare time, I've been starting to plan repairs for the first level framing of my own 100+ year old home. For background, I'm a licensed structural engineer (PE not SE) with about 5 years experience in heavy industry. I work with steel and concrete. My experience with timber design is limited to one undergrad class and sizing a handful of beams and crane mats--so very little practical experience. Virtually zero experience with residential. I'm trying to crunch some numbers so I have a better feel for what's going on in my house and planning to hire a local contractor for repairs.

See attached pdf for a drawing of my house, NDS calcs for a timber beam, and some photos. Below is what I hope to get a little help for:

1) At least one 2x8 floor joist is failing/splitting (photo 1). Joists are old-growth full length 19-20 ft, spanning over a 6x8 timber. No bridging or bracing. I still need to analyze joists per NDS, but I'm planning to sister the failed joist (and a few others) as full length as possible. Anyone see issues with sistering the old joist that is cracked per photo 1? I'll need to reroute electrical. I think I will also install bridging between joists where it's feasible. Some shoring/jacking will be required for this work. I'm assuming driving nails into old wood will be very difficult.

2) My 6x8 timber beam appears to be failing in bending at 350% utilization per NDS... Trying to be conservative, I assumed Douglas Fir-Larch No. 2 with Fb = 750 psi and Fv = 170 psi. Assumed DL = 20 psf and LL = 40 psf. I believe beam is picking up load from second floor as well. Beam is continuous over an S6 steel post at midspan. I assumed pinned-pinned at end connections. Perhaps that's wrong as beam is embedded in concrete wall. Could I call it fixed-fixed to reduce my moment to 7.6 kip-ft? Also, am I being too conservative with assuming No. 2 and Fb = 750 psi? I don't know what's reasonable for a 100+ year old timber.

3) The 6x8 beam has some other issues I want to address. It has a big, ugly notch (photo 2) from an old duct a few feet west of the steel post. I believe notch should be in compression, but it's not code-compliant and definitely not helping my flexure check. I'd like to sharpen my pencil on bullet point 2, and then I can design some reinforcement for that area, perhaps by building a U-shape from 2x lumber to nail from underneath. The beam also has some fairly significant checking (photo 3) on one face only for about 12 ft, starting at the steel post and running east. The other face of the beam has very minor checking. Checking is about 1/2" wide; I can stick my fingers in it. Could this checking be from a more serious issue than from regular drying/shrinkage?

I appreciate any help. Let me know if this type of post is not allowed. I repeat, this is not for work; it's a personal project on my own home.

 

[RattlinBog]

Thanks for the insight ChorasDen. I did review the NDS section about notches, but I'm not sure if I can get it to apply to my scenario. Maybe I'll leave the existing beam analysis as is and move on to reinforcement design. I can only sharpen my pencil so much. And perhaps you're right about the checking/failure on the east half. I'm not really sure how to address it besides reinforcement.

Attaching more photos of the beam for perspective--had to compress photos, so they're a bit grainy. There are a lot of things that are going to get in the way of full length LVL reinforcement. Chimney, water heater, furnace, steel post and cap plate, utility room, pipes, and electrical...some are moveable, some definitely aren't.

I'm currently thinking the best I'll be able to do this is take (4) +/- 12'-0" LVLs (1-3/4" x 9-1/2" perhaps) and sister them on both faces of existing beam on either side of the midspan post. Still need to run these numbers. I'm also considering adding a new post to break up the 12'-6" east span in half. I'll need to be careful about point loading my slab, but it will reduce bending in the beam significantly. See below for existing FBD and proposed FBD with new post. Going to sleep on this for a bit.

Existing: (wood post at 4.92k reaction; beam notch at M=1.84 k-ft)

Proposed: (new post at 6.32k reaction; beam notch at M=2.34 k-ft)

 

[tc7]

Hi RattlinBog-
Your situation is somewhat familiar as I also have a 130+ year old house that was cobbled together with reused timbers and have also rehabbed a few of these ancients in my earlier life. My first thought was that sistering your 6x8 beam with full length LVL's isn't your best option since it seems impossible to get them down to the basement without busting through the foundation.

Is it possible your beam was recycled from some other building at the time your house was constructed and that frightful looking split was "pre-existing", now giving you the appearance that there is a more serious problem than you really have ? Regardless of when or how it happened, I'm impressed at how straight and true that beam appears to be now, leading me to think it may have been resawn & squared-up before being installed in your house. Have you stretched a line to see how much sag you have at the midspans ? I would simply concentrate on adding another post (w/o LVL's) to your existing conditions since the basement appears to be a utility space anyway.

On a side note - your calculation sheets have a very nice format, are they output reports from some commercial software program (if so, which one?) or did you create your own spreadsheet macro ?

Thanks and good luck.

 

[RattlinBog]

tc7, you're definitely right about a full length LVL not fitting in my basement just down the stairs--haha. I should be able to squeeze in a 12 footer, though.

I do agree that, aside from the checking and notch, the beam does look to be in pretty good shape. I have not strung a line yet; I'll do that this weekend. Perhaps you're right that the beam was reused from another structure, etc. Some homes were literally picked up and moved decades ago in the town I live, and there's a small chance that my house was one of those.

I do like the thought of just adding another post, but I'm hesitant to do that and add a concentrated load on my slab. The correct way to do it would be to pour a new footing. I'll talk to a contractor...

These calculations are in Mathcad Prime (I have it at work). My free body diagrams are made in Strian (link: [URL unfurl="true"]https://structural-analyser.com/[/url]). It's really nice for indeterminate structures.

P.S. Talked to an electrician today. It'll be about $4000-$5000 to pull wires out of my joists, clean up some higgledy-piggledy, and update some things to current code--just so I can sister a few joists. Uff!

 

[XR250]

I do like the thought of just adding another post, but I'm hesitant to do that and add a concentrated load on my slab. The correct way to do it would be to pour a new footing. I'll talk to a contractor...

Are there footings under the current posts? I would slam another post under there and be done. If it cracks (unlikely), add a footing later.

 

[jerseyshore]

I do this a ton and by the looks of this beam I wouldn't even bother with it. Your joists aren't even lapped over top here so it's even easier to just add a new LVL right next to it. Shoring wouldn't be needed in that case. You can always add new 2x8 joists to sister any damaged ones.

If your floor is really sagging you can take the risk of jacking it back up first, but if not, just add a new LVL girder and posts right next to the existing one. Put a post right up against the wall on each end to avoid bearing the beam on the wall.

Drill a 1/2" hole in your floor slab and take a wire hanger to see how thick it is. As long as you have 3.5"+ you should be good without it cracking for a long time.

If you wanted to add a footing(s) it shouldn't be too expensive. I had a mason friend do it on the weekend and I think he charged me $500 or less to cut the old footing out and pour a new bigger one.

Forte is the best free software for Trus Joist products and is very user friendly if you're looking for an easy to use wood design program.

 

[kipfoot]

I disagree with the suggestion to add a post without a footing. If you add a post, which you should, put a new footing under it. Then it's done and the future owner of the house won't be back here saying some jackleg installed a post with nothing under it.

 

[jerseyshore]

Yes if you want to do it the right way you should add a footing. But there are a million houses with posts resting on basement slabs and most don't have any issues. If you run a calc for a point load on a slab on grade even with somewhat conservative soil assumptions you'll find that 4 to 5 in. Slabs can handle most house point loads.

But yes you should put footings in. Especially as an engineer owning the house. I ripped out a 2'x2'x14" footing for a new 3'x3'. No one does that unless you're an engineer. I also like the fact that I can bury my baseplate and anchor bolts below the slab instead of tripping over them constantly.

 

[RattlinBog]

XR250, not sure about footings under existing posts--nothing obvious at top of concrete. I'll take jerseyshore's advice and drill a small hole to check thickness.

jerseyshore & kipfoot, I think we're all starting to funnel down to a good solution that's somewhere between overkill and not giving a rip. I've gone from "oh crap my house is falling" to "ok maybe this isn't too bad, and a reasonable fix is available." My wife won't like it, but I think a post is the way to go; it just reduces my moment too much to ignore the advantage. I will add a footing. At the same time, I'd still like to sister/reinforce the beam with either an LVL or 2x...if for no other reason other than to hide give the appearance that I have a beam without visual flaws. As kipfoot mentioned, I am thinking of future owners as well. This is not our forever home. We have a couple young boys and can tell we'll be outgrowing this house in a few years. I'll still crunch my numbers and make the math work--I want to and will do this right; but I don't think I need to do anything over the top.

Honestly, it's looking like the electrical work may be the most complicated and expensive part of this project lol.

 

[jerseyshore]

Utilities are always expensive.

If the wires are near the top or bottom of the joists you could run 2x6s next to the existing 2x8s to avoid having to move wires. Use double 2x6s in that case.

If you're not going to be staying here for a long time I would definitely do things that look good for the future buyer.

Easy for you as an engineer to tell a future buyer "the old floor needed some work so I engineered some fixes after we moved in, have had no problems since" as long as the repairs look legit.

 

[RattlinBog]

Sorry for reviving an old thread. I haven't been on the forum in a while but thought I'd provide an update on how this project is going. All the local contractors I reached out to either didn't return my phone call or were booked up. I decided to do the structural repairs myself, and I'm about 1/4 to 1/3 of the way complete. I hired an electrician to pull wires out of my joists and run temporary wires. Once I'm done with repairs, they'll come back to put wires through my joists and clean up a lot of old, messy wiring and junction boxes. Not cheap, but I think it'll be worth it in the long run for my 100+ year old house.

The repairs have been going well. After finalizing design, I reached out to a more experienced structural engineer friend from the consulting firm I used to work at. He made some recommendations but was overall happy with my plans. I also got a building permit. So far, I have sistered several cracked/twisted joists and also demolished an old, small utility room that was in my way for repairs. I was able to get 2x8 Hem-fir select structural from a local lumber yard for my joist sisters. I'm using Loctite PL 3x premium construction adhesive and Simpson Strong-Tie SDWS framing screws (0.16 x 3") @ 16" O.C. I've been using a post and bottle jack to apply a bit of positive pressure to help equalize load share and let the adhesive cure over 24 hours. I'm providing end bearing to the joist sisters where I can, but it isn't feasible everywhere.

I still have a few more joists to sister, my main beam to reinforce and install posts below, and blocking to install between joists. Some photos attached showing new joist sisters and some ugly joists yet to be repaired at the end. This has been a fun, albeit sometimes frustrating project. Maneuvering around utilities has been challenging, but it's been a worthwhile experience. I'm trying to treat it more like a "hobby" or learning opportunity to enjoy it. It's also been a good excuse to buy some new tools...