Loft Conversion Stairs - Advice on opening width for Trimmer

[TatskyPT]

Hi Guys

I am in the throws of a loft conversion. I am at the stage of dropping in the joists around the opening for the stairs. Setup designed by SE is 4 joists bolted together (175x50mm) at each end, with 2 joists bolted together as a trimmer 2.4m in length.

However, I am unsure as to how wide the opening should be.

Stair treads are to be 800 wide. Should I be leaving a couple of inches(sorry, 50mm) clearance for plasterboard, trimming etc?

I did have an appointment with a company to come out and measure up for the stairs, but they never turned up. I was going to ask them the question.

Incidentally, I know that a concession on loft stairs if the tread can be 600mm wide if the stairs are to 1 room. Does anyone know how keen BC are on this, as I have double winder stairs and 600mm treads would save me 400mm in the stair length, which is a fair chunk of the room my stairs are eating into.

Cheers

tatsky

 

[noseall]

The trimmed opening need only be as wide as the staircase (stringer-stringer) plus 5-10mm fitting gap. This means plasterboard fixed to any partitioning will then drop down onto the stair stringer.

However, if the set-up was a complex winder the i would allow a bit more.

 

[big-all]

just don't forget the strings will add somthing like 60 to 80mm over the tread width

 

[TatskyPT]

Cheers Guys

So is that basically 800 wide tread + 60mm per string +10-15mm fitting gap? So looking like 930mm ish?

 

[big-all]

string will be nearer 32 to 38mm per string[1 1/4-1 1/2"]

 

[TatskyPT]

Exellent, thanks mate.

 

[chappers]

also bear in mind that the width of the stair will be affected by the fact that the winders must have the same going, as the straight treads, along their centre line and must have 50mm at the newel.
Your stair manufacturer will be able to tell you the minimum width possible to meet regs.

 

[TatskyPT]

Thanks Chappers

I did not know that about the same going at center line. I knew about the 50mm at the narrowest point.

After my first joiner no show, I have a company coming out just after new year to measure up.

Cheers for the advice all

Tatsky