OT: structual question with basement beam replacement.

mr douglas t · Post by **mr douglas t** » Thu Jan 03, 2008 5:04 pm

This may be a long question, but I would like to get all the facts out there first. We have a typical wood frame house built in the seventies. We are going to be finishing the basement into living space and I want to remove a few of the steel lolly colums to open up an area in the basement. We currently have a span of 12' with a colum every 6 feet. The beam on top of the colums is a tripple 2x8. I was going to thru bolt two pieces of 1/4" thick, 8" wide steel on either side of the beam and cut/ and remove the center lolly colum. The beam will than be supporting the full 12 feet. I was going to thru bolt the two pieces of steel together every 12', stagering up and down

How does this sound to everyone out there?

Should I use thicker steel?

The beam is supporting the dinning room wall upstairs along with the second floor and a diving wall on the second floor. No roof load is on this beam. Only the interior wals and second floor.

crzypete · Post by **crzypete** » Thu Jan 03, 2008 11:31 pm

Mr D,
I am no expert, but that sounds like it would work. Think of the flitch plate as the web on a I beam- the wood gives it its lateral strength to prevent it from buckling. I would be inclined to use 7" wide steel so that there was no steel hanging below the beams- less work later

The engineer who did the calculations for the beam I flitch plated specced the bolts to be further from the edge than I expected- It was a 2x12 and he wanted the holes 3 or 4 inches from either edge. I believe you will want yours 2+ inches from the edge. Have the steel place pre-punch them for you.

You might ask your steel place if they have an engineer on staff.

Pete

guzziguy · Post by **guzziguy** » Fri Jan 04, 2008 7:58 am

Is your basement heated?

mr douglas t · Post by **mr douglas t** » Fri Jan 04, 2008 9:29 am

The basement is not heated. I was going to cut an extra duct in the current forced hot air system to dump into the basement. As far as the hole punching, I was going to drill them myself. It would be a good excuse to buy a magnetic drill.

nektai · Post by **nektai** » Fri Jan 04, 2008 6:33 pm

Consider punching a hole in the return duct as well to set up proper air flow.

thumb_basher · Post by **thumb_basher** » Sat Jan 05, 2008 3:33 am

G'd Evening, Mr. Douglas...

I've done this on a number of houses. We've always used 1/2" steel flitch plates (by the maximum dimension dictated by the existing beam).

It's important that the steel extend over the vertical members carrying it, as is true of any post and lintel scenario.

Bolt schedule has always been as Crzy noted...2 bolts at each end (2 to 4" from the end of the steel), with bolts staggered up and down in the field. Different engineers have specified different spacing on the bolts, but I've never seen them as close together as 12", so you should be more than fine (typically, they're 24 - 36" apart...).

Some advance notes:
1. Check your existing beam for straight, and make any corrections in advance with a jack or lally column.

2. Clamp your flitch plates together, and drill them together (or have your steel supplier do that...) Torching them is cheaper than punching them, but the holes REALLY suck...sometimes they don't even accommodate the bolts...

3. I usually start with an oversized hole drilled through the wood beam at each end. This allows you to align and adjust both pieces of steel.

4. Through bolting is important. No lags. For alignment, it's best to have a second set of eyes, to correct the direction of your bit as you plow through the wood beam. Those self-feed bits will not be long for this world should you hit the steel on the other side with the feeder point...

5. Put the bolts in as you go...

(Not sure if your magnetic drill press has the capacity, but you MIGHT be able to drill with that???)

Hope this helps!

bldgmovr · Post by **bldgmovr** » Mon Jan 07, 2008 5:37 pm

douglas:
thumb_basher gives good advice above. A wide-flange 8" beam (8x8x31lbs./ft. would certainly support the load you describe. This beam has a web thickness of 5/16" and a flange thickness of 7/16"--I would go with 3/8" plates on either side of the existing triple 2x8 beam. A couple of other points to consider: You will be increasing the loads on the adjacent lally columns by 50% so make sure they have a good base. Also, be aware that the crushing load on the triple 2x8 beam will increase so make sure you have a sturdy plate (at least 3/8"x6"x6") between the top of the lally columns and the 2x8 beam. Re: drilling the 2x8 beam, I find I drill more accurately if I drill half way in from each side (assuming the steel yard punches the holes in exactly the same pattern). Hope this helps.

mr douglas t · Post by **mr douglas t** » Mon Jan 07, 2008 10:47 pm

thanks for all the help, This certainly helps. Some very good points that I did not consider (thicker sturdy plates). I will keep everyone informed on my progress.