Extensive damage to external timber staircase stringer...

[ReneKink]

Hi there,

My external timber staircase needs serious attention.

(Is 30 years old. 13 treads in total, goes straight from a deck to ground. No mid-way structural supports. Stringers are 35mm wide).

One stringer has extensive rot, spray-painted yellow in photos. (Ignore the tarp & I've already taken off the rail and balusters. The post at the rotted section supports the balustrade). Currently, I've a prop under this stringer...

As an uneducated hack of a home handyman, I looked into whether I could cut out the rot & refill, then reinforce the rotted stringer (eg. with a brace on each side going from top to bottom of staircase, or using mending plate, or using a 'flitch' beam) + adding concreted support columns, etc.

Any ideas?? Should I just get the stringer replaced? And would that mean the whole staircase needs to be replaced (because I read somewhere that 1 stringer cant be replaced...)

(For your info, the other stringer isnt rotted. Some balusters need replacing, as do some treads.)
Any comments would be greatly appreciated!

[Pete57]

Others on here have much more experience than me, but this is my take:

Don’t repair. Only option is to replace.
Cannot see why just the rotten stringer could not be replaced by using it as a pattern for the new stringer. Watched my father build plenty of stair cases when I was a kid (he was a builder).

A better option might be replace the lot with steel stringers.

[rwbuild]

Replace the whole stringer, also remove treads from other stringer and see how much rot is in the housing and end of treads too.

[China]

As said above stringer needs to be replaced, you could replace one side it comes down to economics, would be less expensive to replace the entire unit unless of course you can do the job yourself
more than likely when you start disassembly you will find more rotten sections.

[riverbuilder]

Replace it all. Or, trim 40 mm off each end of the treads and replace the stringers only. Use the big galvanized stair angles from Pryda and galvanized 40 mm hex head screws, keep a 10 mm gap between the end of the treads and the sides of the stringer, this lets the water get away and stops rot spores from growing. Paint and seal all ends and cuts.

[verawood]

Welcome RK

[rustynail]

By the time you remove the rotten stringer, cut back the tread ends and refitted everything, you may as well remove the existing and slip in a new stair case. The time spent will be about the same and the end result will outlast a patch up.

[old1955]

Welcome to the forum RK.

For what it’s worth my SIL and I replaced the front steps with gal stringers and new step treads. When removing the old steps more rot was found and the stringers were a bigger mess than I thought.

Regards

Ross

[ScottLands]

I have a similar outdoor staircase. At the time I had a few stringer failures, I owned a steel fabrication business. I welded up 1-1/2 angle iron in a rectangle with a cross member in the center the size of my stair treads and painted them prior to installation. I then screwed the tread boards to the steel frame and used carriage bolts thru the end angle and thru my stringers. It is the strongest my stairs have ever bend. There is zero give in the steps. Now, I own a concrete coatings company and adding polyurea to the wood treads to protect them. It is much better than any sort of wood sealer and should last a lifetime. Plus I can add anti-slip into the coating. I use epoxy too, but not epoxy is not good for outdoor applications. In your case, I would definitely replace those stringers. Check around for a welding shop to make those tread frames. It's a great solution. Good luck. Scott

[Damienol]

I have exactly the same problem that I am half way through rectifying.

The advice given to me by a builder was replace both stringers and reuse as many treads as possible

[GraemeCook]

Pre-made stairs are available from Bunnings. A 13 step unit is priced as follows:

Pine - < $600, and
Merbau - c.$1400.

At those prices it is probably not worth attempting to repair the existing stairs, or to DIY new stairs. Just buy and install.

There are also other potential suppliers. Worth a look.

[Mountain Ash]

Hi RK. Pre made stairs sound like a good idea but they may not suit you. If they have to start and finish at a certain spot then you will be unlikely to get a match. Stairs are always custom made to suit the constraints on site, both rise (gap between treads - including tread thickness) and run (depth of tread) are established first and then stairs made to suit. I agree with those who suggest replacement, if you already have rot and the timbers are all the same, you will almost certainly discover more.