Stairs for semi-d: 2-flight or 3-flight?

[Jack L 0]

Hi friends, my architect designed 2-flight stairs around lift (8 stairs + 9) as below. I heard that 3-flight will be more comfortable to walk (6 + 5 + 6), after all the green part is passageway. 

What's your thoughts? @snooze @George Yeo @AWS and all the great people in the forum. Thank you in advance  

Edited September 20, 2021 by Jack L
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[snoozee 98]

breaking up the stairs into multiple flights instead of one long flight will allow the legs to "rest" when walking along the landing before going up the next flight.

you as the owner can decide on how you want to break up the stairs as long as your architect can design it such that the minimal overhead clearance of 2m between the steps and the above "ceiling" is met.

if I am the architect, I would design the stairs such that the 3 flights will fit nicely around the lift shaft rather than having one step protruding out at the bottom and top then needing to build "columns" to "block" the stairs. so a 5 + 7 + 5 config may fit nicely as well

[IceEyez 4]

5 hours ago, Jack L said:

Hi friends, my architect designed 2-flight stairs around lift (8 stairs + 9) as below. I heard that 3-flight will be more comfortable to walk (6 + 5 + 6), after all the green part is passageway. 

What's your thoughts? @snooze @George Yeo @AWS and all the great people in the forum. Thank you in advance  

Hello!

Maybe it was already resolved, but do note the implications of changing to a 3 flight thing - the position of the door at the bottom room? How are you going to access it if there are steps in front of it?

Also, the width of the remaining space for the pantry area does not look like it is sufficient. Its probably 600mm now? Need to crab walk inside? 🤣

And your tread width is actually very big @ 275mm. You could be saving space with 250mm. The min BCA standard is 225mm only.

[Jack L 0]

5 hours ago, snoozee said:

breaking up the stairs into multiple flights instead of one long flight will allow the legs to "rest" when walking along the landing before going up the next flight.

you as the owner can decide on how you want to break up the stairs as long as your architect can design it such that the minimal overhead clearance of 2m between the steps and the above "ceiling" is met.

if I am the architect, I would design the stairs such that the 3 flights will fit nicely around the lift shaft rather than having one step protruding out at the bottom and top then needing to build "columns" to "block" the stairs. so a 5 + 7 + 5 config may fit nicely as well

Thanks, snooze. Great answer - concise yet insightful. 

[Jack L 0]

2 hours ago, IceEyez said:

Hello!

Maybe it was already resolved, but do note the implications of changing to a 3 flight thing - the position of the door at the bottom room? How are you going to access it if there are steps in front of it?

Also, the width of the remaining space for the pantry area does not look like it is sufficient. Its probably 600mm now? Need to crab walk inside? 🤣

And your tread width is actually very big @ 275mm. You could be saving space with 250mm. The min BCA standard is 225mm only.

Good observation, Ice. Still in the designing stage, so change the door position. 

The panty is a light one serving the floor only.

Specially requested 275mm for comfort, of course, it occupies more space.

[snoozee 98]

24 minutes ago, Jack L said:

Good observation, Ice. Still in the designing stage, so change the door position. 

The panty is a light one serving the floor only.

Specially requested 275mm for comfort, of course, it occupies more space.

Thread width of 250 is quite ok actually. My feet is sized 44 and it feels ok with my stairs of 250 thread width. But since your stairs is wrapping around the lift shaft, ok to use 275 to just make use of the space which would be wasted anyway. Good that you are giving 1200 stairs width as moving mattress up the stairs will be a problem around the bends if it’s just 1000 wide.

if you can increase the walkway of the pantry to 700 would be slightly better. 800 would be best actually. Maybe can consider not having the vertical flutes there to get the extra 100mm. You can find a table, place it at 600 from a wall and see how tight the space is. 

[Jack L 0]

1 hour ago, snoozee said:

Thread width of 250 is quite ok actually. My feet is sized 44 and it feels ok with my stairs of 250 thread width. But since your stairs is wrapping around the lift shaft, ok to use 275 to just make use of the space which would be wasted anyway. Good that you are giving 1200 stairs width as moving mattress up the stairs will be a problem around the bends if it’s just 1000 wide.

if you can increase the walkway of the pantry to 700 would be slightly better. 800 would be best actually. Maybe can consider not having the vertical flutes there to get the extra 100mm. You can find a table, place it at 600 from a wall and see how tight the space is. 

Excellent suggestion for removing the flutes 👍 Thanks, snooze

[yoongf 11]

17 x 175 = 2975mm.

The lower level is abt 3m high floor to floor?

[Jack L 0]

7 hours ago, yoongf said:

17 x 175 = 2975mm.

The lower level is abt 3m high floor to floor?

Yes, it is. Adding a mezzanine reduces the floor height.

[snoozee 98]

15 minutes ago, Jack L said:

Yes, it is. Adding a mezzanine reduces the floor height.

are you doing 6m (1st and mezzanine), 3m (2nd storey) and 3m (attic) or 5.5m + 3m + 3.5m?

normally for beams, they are designed such that the height is much more than the width. so if your beam has a width of about 150mm, the height could be 500mm. so if your floor to floor is 3000mm, you will be left with effective 2500mm floor to beam height. normally for construction, there will be a 50mm offset  such that when the floor finish is done, the floor level will be as per architectural drawings. so this means that you are actually left with 2450mm height from floor to underside of beam after the floor finish is completed. other areas where the floor slab (assuming 200mm thick) will be 2750mm. if you are planning to have false ceiling, then the coverage can only be until the bottom of the beam for a flushed look unless you don't mind exposing the beams here and there.

one way to overcome this height issue is to have the PE design flat beams or design the entire floor slab as a "beam". by flat beams, it will mean instead of a say 150mm by 500mm sized beam, you end up with a wider but shorter beam of about 400mm wide by 350mm height. this will help you gain some height compared to having beams of 500mm or 600mm height.

however, with flat beams, you will encounter another issue when trying to hide the sanitary waste pipes. the P trap of the waste pipes has a height of about 300mm+. with normal beams, this bottom of the P trap will still be above the lowest part of the beams in the room. But if you have flat beams, the bottom of the P trap will be lower than the beam. So you will need to cater for box ups or drop your ceiling even lower to hide the sanitary pipes. So have this in mind when you position your toilets in your house. best if the toilets can be stacked one above each other and you will save headache on placement and hiding of the waste pipes later on since you don't really need to have high ceiling for toilets compared to rooms which is preferred to have high ceiling for better ventilation.

 

[Jack L 0]

18 hours ago, snoozee said:

are you doing 6m (1st and mezzanine), 3m (2nd storey) and 3m (attic) or 5.5m + 3m + 3.5m?

Yes, mezzanine is above the 1st storey. The house is located in a 2-storey semi-detached control area so the total height can't exceed 12m. 

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... so this means that you are actually left with 2450mm height from floor to underside of beam after the floor finish is completed. other areas where the floor slab (assuming 200mm thick) will be 2750mm ... one way to overcome this height issue is to have the PE design flat beams ...

Really admire your detailed analysis 👍 Exactly the case. Will attend the meeting tmr with the architects and PE to see how they address the issue.

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But if you have flat beams, the bottom of the P trap will be lower than the beam. So you will need to cater for box ups or drop your ceiling even lower to hide the sanitary pipes. So have this in mind when you position your toilets in your house. best if the toilets can be stacked one above each other and you will save headache on placement and hiding of the waste pipes later on since you don't really need to have high ceiling for toilets compared to rooms which is preferred to have high ceiling for better ventilation.

Yes, stacked toilets are easy. Will need to see how to handle the unstacked ones. Thanks for highlighting this important issue

[snoozee 98]

1 hour ago, Jack L said:

Yes, mezzanine is above the 1st storey. The house is located in a 2-storey semi-detached control area so the total height can't exceed 12m. 

Really admire your detailed analysis 👍 Exactly the case. Will attend the meeting tmr with the architects and PE to see how they address the issue.

Yes, stacked toilets are easy. Will need to see how to handle the unstacked ones. Thanks for highlighting this important issue

if you are adding a lift to your house, do note that if your attic is only 3m high, your lift options are limited as traction lifts usually need more than 3m overhead. the average overhead requirements is about 3.3m so check and confirm your lift supplier fast so that their structural requirements can be designed into the building plans for submission.

remember that BCA requires a minimum ceiling height of 2.4m for all rooms. if you are not planning for flat beams, then one way is to design the beams such that the coincide with the rooms parting walls and the beams are at the edge of the rooms. then your false ceiling need not drop so much to hide the beams.

toilets not only have the sanitary waste pipes but also the vent pipes. so you need to consider where the main vent pipe goes out from your roof and how to hide this pipe. PUB also requires the vent pipe to be of a minimum certain distance from any windows/openings so if your vent pipe is near to a window/opening, then you will need to put in a very tall pipe to fulfill this requirement.

[Jack L 0]

Quote

one way to overcome this height issue is to have the PE design flat beams or design the entire floor slab as a "beam". ...

however, with flat beams, you will encounter another issue when trying to hide the sanitary waste pipes. the P trap of the waste pipes has a height of about 300mm+.

PE proposed UC beam and the height will be around 350mm. For the P trap issue, will see how it will be worked around later. Thanks for bringing it up, @snoozee. 

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do note that if your attic is only 3m high, your lift options are limited as traction lifts usually need more than 3m overhead. the average overhead requirements is about 3.3m

You are quite right. URA allows protrusion up to 0.5m. BCA enforces SS 550:2020 compliance for all plans submitted after 1 July 2021, which requires even higher headroom. Schindler raised the min headroom from 3.5m to 4.1m due to this code. Small players requires min 3.5m. My architect suggests getting a waiver from URA for higher protrusion.

I have been shopping around and found that a 1m/s traction glass lift with 5 stops costs from 60K to 90+K, annual maintenance is from 2K to 3K.

[snoozee 98]

16 minutes ago, Jack L said:

PE proposed UC beam and the height will be around 350mm. For the P trap issue, will see how it will be worked around later. Thanks for bringing it up, @snoozee. 

You are quite right. URA allows protrusion up to 0.5m. BCA enforces SS 550:2020 compliance for all plans submitted after 1 July 2021, which requires even higher headroom. Schindler raised the min headroom from 3.5m to 4.1m due to this code. Small players requires min 3.5m. My architect suggests getting a waiver from URA for higher protrusion.

I have been shopping around and found that a 1m/s traction glass lift with 5 stops costs from 60K to 90+K, annual maintenance is from 2K to 3K.

besides the P trap, you also need to think about your aircon pipes as well. How you are planning to route the gas pipes from each room to the aircon ledge where the compressors are and how to hide the pipes that goes underneath the beams. So this will also play a part in your ceiling height and box up. proper planning of aircon height placement will also let you avoid the ugly "wearing of hat" where a part of the false ceiling is recessed upwards to cater for the aircon indoor unit.

the big players like shindler, kone are geared towards commercial sector so there won't be an issue with overhead. even hitachi/mistubishi isn't interested in dealing with home lifts when i enquired with them when sourcing for my home lift. there are many companies focusing more with home lifts in the market so you can search for these instead. pricing is very competitive among these smaller players. if you want to have glass lift shaft then you must be prepared to pay for it since the lift shaft would need to be built separately using steel columns and beams.

 

[Jack L 0]

On 9/23/2021 at 4:39 PM, snoozee said:

besides the P trap, you also need to think about your aircon pipes as well. How you are planning to route the gas pipes from each room to the aircon ledge where the compressors are and how to hide the pipes that goes underneath the beams. So this will also play a part in your ceiling height and box up. proper planning of aircon height placement will also let you avoid the ugly "wearing of hat" where a part of the false ceiling is recessed upwards to cater for the aircon indoor unit.

Thanks, @snoozee. At what stage should those details be specified? I am currently at schematic design and no plan has been submitted yet.