Some claim to be weatherproof, e.g. https://www.aluminiumtradesupply.co....-weatherproof/
We are having a rear extension next month and having ubiquitous bifold doors.
We would like seamless transition from the inside of the house to the patio. Effectively the inside floor bifold sand patio are all flush, to create the appearance of a single space flowing into the garden.
The structural engineer came around yesterday to measure up for the structural plans and did not recommend this as he said it is very difficult to make the bifold truly weatherproof.
Anyone have this set up and can comment with their experience?
Some claim to be weatherproof, e.g. https://www.aluminiumtradesupply.co....-weatherproof/
We received the very same advice when having our bifolds installed and I can see the sense in it. We have a very small lip (approximately 1-inch) and it doesn't detract or seem to cause us any issues at all.
I have clients who ask for this all the time and recommend against it. It’s fine in the Med but here we just don’t have the climate. So far as I know there are no door companies that will guarantee a water tight flush cill in the UK. You can bring your patio up level with the internal finished floor level with a normal low threshold cill but make sure there is some form of permeable break between the door frame and pavings. For example an Aco channel or loose stones. Obviously don’t bridge your DPC whilst don’t this.
The one client I did have who went against the advice of the door company and fitted a flush cill did have leaks from time to time.
Last edited by benny.c; 19th May 2018 at 11:32.
Thanks. I’ve just got some technical drawings from Kloeber, one company we are considering.
They illustrate a 74 mm (3”) lip above the finished floor level. Is this a little on the large side?
My house has them. The doors were already here when I bought the house and were installed 8 years ago.
They’re from
https://www.foldingslidingdoors.com/
I have a patio outside and have never had any issues at all in the 18 months I’ve lived here . With kids I much prefer it over the step down I had in my old house as they run in and out of the house and don’t have to worry about tripping up.
If I was fitting them again I would do them as they are.
Here's the technical drawing I have from Kloeber. As you can see it's a 74 mm lip from the top of the inside finished floor and a 88 mm (129 -41) lip from the top of the outside patio
The structural engineer was also concerned that the patio was above the bottom plastic board. If we put the plastic below this then the lip to patio would be 162 mm (129 + 10 + 26) or nearly 6.5" in old money.
What's the thoughts on this? Can the patio be raised above the plastic bottom board? What's the best way to get it as flush a possible without compromising weather tightness, and which doors should we look at in that case?
Origin are good,the cull on the drawing won’t be there as you would order them without it ,we always do them so there about 20mm higher than the patio and put a slot drain in front
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It's actually only a 5mm lip above the FFL. The 69mm is the folding door frame, so yes it will be 74mm when closed, but only 5mm when open.
Besides, that looks like a sliding door section detail to me.. edit: Actually, could be bi-fold.
In fact, you'll be struggling to better that and retain watertightness. If you look at the external level you would have 14mm between the internal and external FFLs with a 5mm lip on both. Pretty good.
Last edited by Nuisance Value; 19th May 2018 at 15:40. Reason: misread drg; more detail
I actually thought it was the other way round!
The main conclusions we came to when researching which ones to get was go aluminium, go German and DON'T have built in blinds.
Inside - Outside
Outside - Inside
I've included our 2 year old's feet for the purposes of illustration! (model's own)
Last edited by MST; 19th May 2018 at 18:12.
We're right. I've just been through this with my own place and have spent hours checking sections to get the right heights on a sliding door install / window reveal sightlines etc.
To add to this it's critical that the base course (external block leaf) and internal floor slab / screed / floor covering is bang on height wise, as this will determine the overall height it sits at.
I'm sure I've read that it's good practice to sit folding doors on a steel beam, one to get the height right and secondly due to the forces / weight of the door leafs on folding doors do not overstress block / brick on the outer leaf. I know of one national house builder that won't fit them anymore due to this.
It's not easy to get bang on.
Technical issues now resolved, please see the pics of our threshold in my reply above.
Thanks all. 5 mm lip it is then.
As a Chartered Engineer myself with some 27 years experience, you’d think I could read a technical drawing!
As a Surveyor, quick tip ask for the threshold to be wheelchair accessible or DDA compliant. It’ll most likely have a 12-15mm ramped threshold for weathering but that should be pretty good all round. Internal FFL and external GL can be the same level. Good luck.
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Just curious, you do realise the 74mm you quote in the drawing is from the finished floor to the top of the bottom rail on the door. When the door is open the threshold would only be 5mm above the floor. similarly the patio would only be a few mm below the outward side of the floor track. This is the best solution and there is no problem the patio being above the cil as long as the water can drain. IMHO this is a good way of achieving a low threshold without compromising the weatherproofing and we have fitted this several times with no problems