cracked basement stair stringer

[pete kahn]

I was bringing an engine down in my basement. I heard the stinger crack at a knot. What is the correct way of fixing this? I want to do it the right way. Thanks in advance. Pete

[Gunnar Alquist]

Difficult to say for certain from a single photo. I am sure that there are many possibilities. One would be to replace the stringer and another would be to "sister" an additional, full-length, member alongside the damaged one. But, this is based on limited information.

[pete kahn]

Gunnar thank you for your quick reply. The "full length" is a must? Would it be a bad idea to brace it with a partial length brace (either wood or steel)?

[John Arnold]

Shove the engine under the stringer?

[pete kahn]

I had not thought about shoving the engine under the stringer. I was thinking of making a bracket by welding four feet of 3" flat stock to four feet of angle iron to make an "L" shaped bracket. Then using this bracket to support both the side and beneath the broken stringer.

[Jack Feldmann]

If this was mine (based on my own basement stairs), and I couldn't get a full length sister stringer....I would sister the longest board I could to the side of the damaged stringer. Then I would add a cross brace in the area of the split, and install a vertical 2x4 to provide additional support.

[pete kahn]

This is what I ended up doing. I bolted a large angle to the stringer. . It was "L" shaped. I tightened large clamps on either side of the angle to bring the crack together. Then I used steel bolts with large washers on either side to tighten it up. Thanks for the advice. If this is a bad idea, I would like to hear about that too. thanks. Pete

[Jerry Peck]

If this is a bad idea, I would like to hear about that too. thanks. Pete

As done, I think it is a 'bad idea' because you have reduced the effective depth of that stringer down to the width of that 3" angle or flat stock.

That metal alongside the stringer should be the full depth of the stringer. As to the length of the metal repair, probably at least 2 feet *past* the *ends* of the split.

Another option would be install a support column under the center of the split along with your metal repair as that way the load if carried on the column, but there is no footing under the column, so that is not a good repair, just a 'temporary' repair.

As pictured, I would not take that engine back up those stairs, the stringer will likely split the rest of the way.

[pete kahn]

Jerry.. what you are saying makes a lot of sense. I had thought about putting a vertical metal piece to support the angle, but you are correct there is no footing. So, now that we both agree that my fix is temporary.. what is the best way to fix that crack in my stringer? thank you for your help.

[pete kahn]

And.. there is no footing where the bottom of the wooden stairs rests on the basement floor. :)

[Stephen G]

Pete, nice work, although...
I know that the 3 angle iron you used was just laying around the shop and everything just cost you your time. Did you use big washers on the other side to stop the nuts from crushing the wood? Flat stock maybe. :p
From that one picture it looks like you have lots of room to 'sister' a stringer down that side.
The existing stringer has one to many knots and is know useless, your plating the spine of that stringer should last as long as it takes you to go buy a new pc of 2x to atach it to the busted one. As Jerry mentioned youve only strengthened the area above the angle iron.

[pete kahn]

Thank you Stephen.. So, the correct way to fix this is prop up the damaged stringer and then take a new 2x and glue and nail is (sister) it to the damaged stringer? thanks. Pete

[Stephen G]

Thats what I would do. I would never have let you have those steps without having sistered the stringers in the first place, regardless of the knots.
Your pretty handy guy so this shouldnt be a problem.
Match the angles at bottom and top of the existing stringer, measure the length of that stringer and then transfer those angles and length to the sister. Measure this bad boy and then measure again, scribe your marks, measure again, and then cut. Wood is not as forgiving as metal:D
I would sister both sides, they should be the same angles and its cheap at twice the price...

Hope this helps

[Vern Heiler]

I'm not an engineer but I would be surprised if the stringer wouldn't break past the ends of the angle iron before it broke at the original split. TJI joist get there strength from the top and bottom flanges, tinsel and compression. The center of the joist, or stringer in this case, provides little of the total strength and the metal angle provides a great deal of tinsel strength.

[pete kahn]

Stephen, Thank you for your kind words, and your great advice. I have gotten bitten by the "carefully measure the wood monster" a few times. So, maybe I will buy 4 2x's just in case! Why did you say that you "would never have let you have those steps without having sistered the stringers in the first place"? To be honest before I broke the stairs I would have thought that nothing was wrong with them. I am guessing that this has something to do with why I am doing both sides, even though one is broken. thanks.. Pete

[Vern Heiler]

The reason it broke in the first place was a poor choice of lumber. The large knot that goes all the way to the edge of the board. No tinsel strength!

[pete kahn]

Vern.. I agree with what you said. These crappy basement stairs have never felt as strong and stiff as they do with the 1/4" thick angle that I bolted to it. I should remove the whole piece of crap staircase and weld a metal one. That being said.. I wanted to find out what the "right way" to repair the stringer was. This is why I asked on the inspection news forum.

[Stephen G]

The stringer is split. Knots and heavy point load (350 cid chevy block undressed about 350 lbs) two guys (big guys) muscle it down. One more heavy load, regardless of the scabbed iron, will increase the existing split. Stairs are now dangerous. Like scissors the stairs will fold on that one side. Right now it has the compressive strength of a hinge, Or ball peen hammer with a 'u' joint.....:D :D :D


I'm not an engineer but I would be surprised if the stringer wouldn't break past the ends of the angle iron before it broke at the original split. TJI joist get there strength from the top and bottom flanges, tinsel and compression. The center of the joist, or stringer in this case, provides little of the total strength and the metal angle provides a great deal of tinsel strength.

[Vern Heiler]

Unfortunate for you, our job is to identify problems, we are supposed to defer the corrective action to a qualified individual (licensed engineer). Sorry but you have my best guess, take it for what its worth:) .

[Stephen G]

Pete, as Vern alluded to we try and direct you to the answer as best we can with limited information. So there are some greay areas.
A new set of properly built stairs sounds like what you need. Wood or metal is your call, and wallet. It shouldnt take you long to get a skilled licensed, experienced carpenter to build you some routered double up stringers and steps. I am partial to wood, but if its the garage metal may be your answer

Good luck

regards






Stephen, Thank you for your kind words, and your great advice. I have gotten bitten by the "carefully measure the wood monster" a few times. So, maybe I will buy 4 2x's just in case! Why did you say that you "would never have let you have those steps without having sistered the stringers in the first place"? To be honest before I broke the stairs I would have thought that nothing was wrong with them. I am guessing that this has something to do with why I am doing both sides, even though one is broken. thanks.. Pete

[pete kahn]

Thank you again.

The more I learn, the more I learn how little I know. -- Socrates

[Jerry Peck]

Thank you Stephen.. So, the correct way to fix this is prop up the damaged stringer and then take a new 2x and glue and nail is (sister) it to the damaged stringer? thanks. Pete


Thats what I would do. I would never have let you have those steps without having sistered the stringers in the first place, regardless of the knots.
Your pretty handy guy so this shouldnt be a problem.
Match the angles at bottom and top of the existing stringer, measure the length of that stringer and then transfer those angles and length to the sister. Measure this bad boy and then measure again, scribe your marks, measure again, and then cut. Wood is not as forgiving as metal:D
I would sister both sides, they should be the same angles and its cheap at twice the price...

Hope this helps

Yep - cut two new stringers for each existing stringer, glue, nail, and through bolt from the new stringer on the outside of the existing stringer all the way through the new stringer on the inside of the existing stringer and bolt everything nice and tight.

If you want to make an extra strong stair, make a flitch plate and sandwich that between the new sister stringer and the existing stringer on each side. A flitch plate is like this: (scroll down to page 9) http://www.toolbase.org/PDF/DesignGuides/flitchplate.pdf

Except your flitch plate will be notched to match the stringers.

[pete kahn]

Thanks Jerry. I appreciate your sharing your knowledge. I will have to read over that flitch plate information you send me. Thank you for that too. Yes., I would like the stairs to be extra strong. The engine that I brought down the stairs is hardly the heaviest things I have down there. Thanks Pete

[BridgeMan]

Based on the OP's pix, treads and risers are inset into stringers, so no notching (of anything) is required. Steel flitch plates would certainly do the trick, but I suspect simply adding a bottom 2 x 6 wood flange across the doubled-up stringers on each side would be just as effective, while not weakening things by making Swiss cheese out of the stringers.

[pete kahn]

Thank you BridgeMan.. with all this great advice, my staircase is going to outlast the whole house! thanks Pete

[Vern Heiler]

Thank you BridgeMan.. with all this great advice, my staircase is going to outlast the whole house! thanks Pete
Pete, take advice from a fool. You need to start thinking in terms of hoist or lift if engines are not the heavest things you have hauled up and down those stairs. If you don't think injury, think liability!

[pete kahn]

Vern, I have given a little thought injury, but I never even considered liability. May I ask what would be the liability to me when I drag heavy stuff in and out of my basement? Also.. the only hoists that I have seen for stairs are used to bring seniors up and down? I have a floor crane in my garage, but nothing for the basement stairs.

[John Kogel]

Rather than hoisting straight up, I would look at anchoring a winch of some kind past the top of the stairs so that you can drag heavy stuff up. Lay down skids to protect the steps.

But first, add those wood sisters. One reason the wood gave out, beside the knots, is that the sides were routered out to accept the treads. The wood was too thin there.
With 2 X 12 sisters glued and screwed, there is probably no need for a post under the middle.

[Vern Heiler]

Vern, I have given a little thought injury, but I never even considered liability. May I ask what would be the liability to me when I drag heavy stuff in and out of my basement? Also.. the only hoists that I have seen for stairs are used to bring seniors up and down? I have a floor crane in my garage, but nothing for the basement stairs.
I was assuming that 300 + lbs. in and out of the basement you might have help. If not ........ can we be friends:) ?

[pete kahn]

John...I cant wait to give the wife the good news that I am finally installing a winch in her kitchen so that I can get stuff in the basement with out breaking my back! I will add the wood sisters. I may not be able to get to it until this weekend. Hopefully I wont break anything else until then! Pete

[pete kahn]

Vern.. I actually brought the engine down the stairs on a hand truck. It is not the first time I have done this. The trick is not to be in front of the engine as I go down the stairs. It didnt occur to me that a knot would be a weak point. I just never thought of it. In my next life I will find hobbies that dont require big heavy metal things, but in this life it's just not the case. :)

[Jerry Peck]

Based on the OP's pix, treads and risers are inset into stringers, so no notching (of anything) is required. Steel flitch plates would certainly do the trick, but I suspect simply adding a bottom 2 x 6 wood flange across the doubled-up stringers on each side would be just as effective, while not weakening things by making Swiss cheese out of the stringers.

I was thinking of adding the flitch plates to the inside so as to put the support directly under the treads and no rely on the tread/stringer connection. The side benefit of putting the flitch plates inside the strings is that the stairway does not get wider and take up more room, and that the tread span actually gets shorter - meaning that the treads themselves are stronger too. :cool:

[BridgeMan]

I was thinking of adding the flitch plates to the inside so as to put the support directly under the treads and no rely on the tread/stringer connection. :cool:

If O.P. Pete decides to use notched steel for the repair, he needs to factor in the added labor cost of custom-notching thin steel plate in addition to the bare steel cost, unless he's an experienced metal worker and can do it himself. Flame-cutting thin steel while preventing significant biplanar distortion (to the point of being difficult to accurately draw up against the stringer) could prove to be a challenge. At least it was at the fabrication shops I worked at, as an AWS-CWI. I spent more than a few hours observing frustrated fit-up crews trying to assemble steel stair assemblies. Lots of heat straightening required, even when using cutting tables with multiple hold-down jigs.

Straight, plain steel is a better way to go, and no steel at all could be just as effective while being easier to work with, as mentioned in my earlier post.

[Jerry Peck]

If O.P. Pete decides to use notched steel for the repair, he needs to factor in the added labor cost of custom-notching thin steel plate in addition to the bare steel cost, unless he's an experienced metal worker and can do it himself.

From his posts, I figured he could handle that.


Flame-cutting thin steel while preventing significant biplanar distortion

How thin are you talking about? I've cut some 1/4" stuff in playing metal shop worker for some of my own project years ago and never had that problem.

'Course, though ... :p ... *I* was thinking of cutting it on a band saw. ;)

Anyone who hauls engines up and down into and out of his basement as got to have a pretty well equipped shop (at least in my opinion).


I cant wait to give the wife the good news that I am finally installing a winch in her kitchen

I was thinking of a wire rope system with a pulley on each side of the top of the stairs, with the winch and all the other workings in the basement - the wife would never need to know why that 'clothes line' was so low along the stairs that she can't use it. :)