What timber would be suitable to use as indoor stair stringers?

[shepperd]

I'm in the process of creating a set of stairs to an open loft in a bedroom (a platform that spans 1/3 above a bedroom that came with the house) and have completed my calculations and design according to the NCC wrt stair and landing construction. I am now looking at selecting an appropriate type of timber for the use as stair stringers.

The stringer length must be 3.6m long and will run along a brick wall, so one side will be chemset and the the other will be fixed at the top and bottom of the flight and will have 9 goings (including top step).

My thoughts right now are to use some H2S 300x63 LVL as it will be relatively cheap (about $50/Lm) then paint and use some DAR for the treads.

Is there a better way of going about this?

[MitchellMc]

Hi @shepperd,

Your approach of using H2S 300x63 LVL for the stair stringers sounds reasonable from a materials and cost perspective, as LVL offers good strength and stability for a job like this. Using dressed all round (DAR) timber for the treads is also a solid choice, especially if you’re planning to paint or finish them nicely.

That said, stairs are a critical structural element with safety implications, and the calculations and design requirements under the NCC can be quite complex. Typically, these sorts of calculations and structural approvals are best done or at least reviewed by a qualified structural engineer or an experienced builder. They can verify that your design meets all load, span, and safety standards, especially since your stringers are fairly long at 3.6m and fixed on one side to a brick wall.

If you haven’t already, I’d recommend reaching out to a professional to review your plans to ensure everything will be safe and compliant. It’s better to be cautious with something as important as stairs. 

Please let me know if you have any questions.

Mitchell

[shepperd]

Hey Mitchell,

Thanks for confirming this! I agree that a builder will be confirming the design prior to commencing the project, however as a structural engineer myself (Mechanical though, not Construction/Civil) I do believe the design will be safe and conform to the standards.

I suppose the question was aimed at getting a better idea of what materials are commonly used in projects such as this as I have little experience in this area myself.

Thanks again for your help!

[MitchellMc]

You're on the right track using LVL's @shepperd. You're unlikely to find solid pine of those calibres, so if you were to drop the dimensions down to accommodate it, you'd likely then require a support midway. For instance, we only carry up to 190 x 45mm Framing MGP10 Untreated. It's also rougher-header so it has milled lines in it. Not really something you'd use for an exposed stringer that you were painting. We don't carry DAR in those calibres.

Let me tag @Nailbag for his thoughts.

Mitchell

[Nailbag]

Hi @shepperd 

I have to be honest, the exacting details of materials and specs is not my area of expertise when it comes to stair building. in the past I have always referred to my draftsperson to specify the requirements and build to that.

To your point of being a mechanical structural engineer, I am sure your calculations will be well with in structural integrity. I would simply ensure it actually complies with build codes and any owner builder requirements for this project in. your state.

Nailbag.

[shepperd]

Hey @Nailbag,

Yeah that makes sense! The plan will definitely go through a checking/review process with the builder to ensure it ticks all the boxes, I agree that it's a crucial step in the process.

Appreciate the feedback!

Cheers!