Bifolds for garden room - low threshold OK?

[Molynoox]

I have just ordered some 'Cortizo / Ezifold' bifolds (and some other stuff) for my garden room build
They do have a rebated sill option, but I have been recommended a low threshold sill by the supplier. I have some concerns that this will not be fully weather proof. I do have a 400mm canopy, which may help to stop excessive amounts of snow from sitting adjacent to the door, however, this will not prevent all water from hitting the door, it still needs to be weather proof

The supplier ensured me that any water hitting the door would run down it then successfully clear it and not enter the building, and that the only way for water to enter the building with the low threshold is if the water is allowed to build up outside the door, like a deep puddle, and then 'overflow' into the room (hence my comment about snow build up)

I don't think water will be able to 'pool' outside of the door in my design because I will have a decking path on outside and I will leave something like a 10mm gap to the door which would allow water to drain off the decking

Is a low threshold sill suitable for a garden room application such as this?
I know I could get the rebated version and be done with it, but I do like the idea of a low threshold to keep things flush, so I would like to explore this option
I have asked them for the technical drawings of all options so I can evaluate this better but they haven't sent those through yet

your comments are much appreciated

thanks
Martin

 

[RobinBHM]

without a rebated cill, the draught seal must act in a wiper fashion -at least that is my guess.

in my opinion wiper seals are less effective and prone to wear.

in terms of a water seal -it probably works fine as there must be a drip groove under the door which will force the water to run down into the cill channel and exit via a hole somewhere

depending on aspect your roof overhang will reduce rain on the doors by a huge amount -I have a 600mm overhang on my garden cabin and its a fantastic addition, the doors and windows get almost no rain on them -just the bottom 18"

 

[porker]

I recently fitted one to the house and although there was no advantage to me for the flush sill (because the inside floor level is lower than outside), what I read was effectively as @RobinBHM states above and rain can blow under the door and the seal is unlikely to remain optimal. Going by your drawing though, if you can make the outside finished level below that of the sill to avoid water collecting near the seal I would think you would be OK. The main issue is to have a drip on the door and no way of the water to collect at the bottom.

 

[Molynoox]

without a rebated cill, the draught seal must act in a wiper fashion -at least that is my guess.

in my opinion wiper seals are less effective and prone to wear.

in terms of a water seal -it probably works fine as there must be a drip groove under the door which will force the water to run down into the cill channel and exit via a hole somewhere

depending on aspect your roof overhang will reduce rain on the doors by a huge amount -I have a 600mm overhang on my garden cabin and its a fantastic addition, the doors and windows get almost no rain on them -just the bottom 18"

hadnt thought about the wiper seal situation - thats a good point, I will be able to check that once I see the drawings

 

[Adam W.]

Put in a land drain or gutter type thing directly in front of the cill.

 

[Molynoox]

I recently fitted one to the house and although there was no advantage to me for the flush sill (because the inside floor level is lower than outside), what I read was effectively as @RobinBHM states above and rain can blow under the door and the seal is unlikely to remain optimal. Going by your drawing though, if you can make the outside finished level below that of the sill to avoid water collecting near the seal I would think you would be OK. The main issue is to have a drip on the door and no way of the water to collect at the bottom.

yeah I'm thinking I can have the level lower on the outside, so it could be possible.
still not decided on this - hmmmmm

 

[Molynoox]

Put in a land drain or gutter type thing directly in front of the cill.

good idea but might not look very brilliant...

 

[Adam W.]

It looks fine with a 4" strip of shingle covering the drain then paving up to that

 

[Molynoox]

that could work, nice idea

 

[Adam W.]

I've done it a couple of times and it looks pretty neat.

 

[Molynoox]

Don't suppose you have any pictures?

 

[RobinBHM]

Unless you are having the external surface level with the inside finished level, I personally would choose a rebated cill.

You can set the top of the rebate level with your internal FFL.


Externally if you want to avoid a step with a traditional cill, you need an aco threshold or slot drain - which involves a fair bit of hard landscaping and surface water drainage system....i.e going to a soakaway.

 

[Molynoox]

cheers Robin
not sure how I get FFL to height of rebate? if rebate is say 35mm and floor is 12mm + 5mm underlay, that is a big gap to make up somehow....

 

[Woody Alan]

https://www.slideandfold.co.uk/threshold-details-for-bi-fold-plus-liniar-doors.htmlLook at the drrawings side by side and you'll see the difference is the lip on the normal threshold has an upstand the door closes on. I have fitted a low threshold in my garage and had no issues they are just covering themselves.
This site has some really good technical drawings just not easy to find.
This low threshold with cill https://www.slideandfold.co.uk/Bifold-Plus-Threshold-Low-Threshold-180mm-Cill.pdf

 

[Molynoox]

thanks, that has helped. I have now received the actual drawings for the product I have ordered - with both options. Seems like the seals on low threshold are little brushes by the looks of the drawing.

I also found quite a cool picture of what Adam and Robin are talking about - even with rebated cill it sits very flush, you are only looking at +12mm for the rebated option compared to low threshold, which is nothing really. As long as I can get the FFL up to height and can build outside levels up to the right height then I think this works pretty well

not sure what to do with the water from the drain now....

 

[Adam W.]

Don't suppose you have any pictures?

I don't have any pictures, but it just looks like a 4" strip of shingle before the threshold. The drainage was simple, as I just hooked it into the roof drainage pipe.

I made the hard landscaping slope gently away from the extensions, so the drain only had to deal with wind driven rain. They were both in sheltered locations though.