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Width of stair stringer

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Ponder

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can anyone tell me what width of timber should be used for cutting a cut string residential indoor stair stringer? Was looking at 32 x 244 as you can buy that as standard from e.g. pear stairs but then started wondering if its different for cut strings and I can’t seem to find confirmation online!
 

yetloh

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No expert, but surely it depends on the travel and rise rates of the stairs because these are usually housed into the string, and of course you need a bit extra above and below the housings. As for the depth of the housings, I wouldn't want these to be less than about 15mm. Cutting all these housing accuarately is not a minor undertaking. I believe there are router jigs for this job but I doubt that they are cheap

Jim
 

TRITON

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I think 50 x 250 is about the standard size. I've made one staircase decades ago and that was what I did it at.
 

Cabinetman

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Hi Ponder and welcome, again it’s a while since I did it. Cut string doesn’t involve any routered housings afaik.
Obviously as was said travel and rise make a difference to the amount of timber left after removing the triangles. The treads and risers do add a little stiffness to the string, but I do not think I would want any less than 4 1/2” left uncut but there are charts for the exact dimensions of stairs.
My advice to you btw is don’t fall in lol. Ian
 

Ponder

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Hi Cabinetman, thanks for the welcome! Yes no routering, just cutting out the birds mouths essentially. Rise is approx 217mm and tread approx 227 but can’t quite remember! Will have to have another look at the drawings And see if there’s 4.5 inches left. I’m not sure which charts you mean.

do you have any thoughts on thickness also? I see Triton has recommended 50mm, thanks!
 

Cabinetman

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Hi Cabinetman, thanks for the welcome! Yes no routering, just cutting out the birds mouths essentially. Rise is approx 217mm and tread approx 227 but can’t quite remember! Will have to have another look at the drawings And see if there’s 4.5 inches left. I’m not sure which charts you mean.

do you have any thoughts on thickness also? I see Triton has recommended 50mm, thanks!
Well, sorry "it depends " on all sorts of other variables but in a domestic setting I think 32mm would be enough.
Will see what I can find re charts. Ian
 

baldkev

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There was actually a thread ages ago on a cut string staircase, it was a great job.
Welcome to the forum
Kev
 

Ponder

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There was actually a thread ages ago on a cut string staircase, it was a great job.
Welcome to the forum
Kev
I did find one about a lovely oak staircase, far beyond what I will be doing but very inspiring!
 

Doug71

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I have just measured mine I made a few years ago and it has 5" solid left behind the cut outs.

I can't remember the thickness I made mine and it's all boxed in so can't see. I did just look in an old Purpose Made Joinery book and it shows 38mm cut strings but no harm in going thicker.

There was actually a thread ages ago on a cut string staircase, it was a great job.
Welcome to the forum
Kev
There was also a thread where someone asked why the spindles were coming out of their cut string staircase, when they showed the photos there was only about 1 1/2" of solid left under the treads, it looked like it could snap in half at any time 😮
 

baldkev

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Yeah, i wasnt going to mention that one 😆 poor chap
 

Jones

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Looking at span tables for roofing a c24 rafter at 30 -45 degrees would span 3.47m for a 47mmx150mm at 600mm centres. The risers will add alot of strength as will using something like oak but I would leave at least 4inch of uncut timber
 

Jones

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To avoid buying a full width stringer you can use the offcuts to build up the triangles, best to draw it out on graph paper first.
 

Cabinetman

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That’s pretty comprehensive Pete, just to say though it’s American codes (standards) so may not be exactly to UK building regulations. The American standard may actually be higher than ours! Ian
 

redhunter350

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We made these last year from Oak the strings were about 45mm I will have to check. No jigs just a home made template for routing the tread mortise and very careful marking out ! All drawings done longhand to scale

14E5F481-BEE0-43B9-8809-F4A8A09B967B.jpeg
AACB4951-D460-459D-9738-80974D9B5126.jpeg
 

Jones

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Looks good but they definitely don't meet building regs
 
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