Architect says External Glazed Sliding Pocket Doors are "Impossible in a Timber Frame"

[thefoxesmaltings]

I have been told by my architect that it is "impossible" to have an external sliding glass pocket door with timber frame construction. Something I honestly thought was pretty standard.

 

My architects comments when I asked to make the change on the drawings:

"This would be impossible due to the inability to waterproof and insulate properly, and that we would need a very large steel above in order to cover almost 8m of opening. This would mean also using posts and boxes in order to cover everything, and quite frankly would just look unsightly and be awkward to construct."

 

The total length of the proposed glass sliding door is 6m, with 3 panes...nothing I would class as out of the ordinary. We would need a steel beam there anyway, due to the 6m span. I envisioned a small extra cost for additional steel in the span, and also the small cost of the extended track. However, overall, I would have expected the cost difference to be pretty minuscule.

 

Each pane is approx 1980mm and the width of the wall for them to slide into is approx 2400mm. I had planned for the 3 panes to slide from right to left. It seems like we have enough space to house the doors within the wall?

 

Has anyone successfully planned or installed a large external glass pocket slider into a timber frame house? Or alternatively can provide me with some drawing detail or ammunition to go back to my architect with? 

 

 

Image below for example:

[CharlieKLP]

I have looked at pocket external doors with timber frame (with a timber frame expert), and I’d have to agree with your designer, it’s hideously complex  and makes for very thick walls and insulation/structural issues.
 

I don’t think it’s ‘impossible’ but listen to the designer when they are trying to stop you doing costly and unsightly changes, they aren’t doing it to be awkward!

 

You have a great design and I’d say they don’t want you to ruin it.

Edited June 7, 2022 by CharlieKLP

[ProDave]

If you are going to pursue this, there is one word you need to understand.  COMPROMISE.

 

If you slide all 3 panes into a pocket on one side, that will take up a lot of the width of the frame of the house.  Much of that width would normally be filled with insulation.  By leaving a gap there (that is what you are doing, leaving a great big open gap in the wall occasionally filled with the doors) you compromise on the amount of insulation so that part of the wall will be cold.  You might look at making that section of wall thicker to get that insulation thickness back?

 

But the big one for me is air tightness.  If as in your example photo just one pane slides into a pocket, then you might be able to design the window frame so it makes a reasonably air tight seal whether that pane is slid into the pocket or slid into normal closed position.  But you want all 3 to slide into the pocket.  Just how do you think you are going to get anything like an air tight seal around a hole in the wall 3 panes wide, when they are all shut, and only 1 pane is filling that hole? 

 

Find a real world example of 3 panes sliding into the same side and come back and show us how they did it.

[redtop]

Not an expert enough to really known the answer.... But couldn't you construct the wall using 2 timber frames with the gap between for the sliding doors. As is, the 2nd timber frame would be on the inside and just be used to create the gap for the doors, effectively a larger service void. Yes that wall would be thicker but not really sure why it would be anymore complex than doing the same with brick wall.

[Conor]

If you want to maximize the clear opening, go for bifolds. Our triple glazed Solarlux are excellent.

[SteamyTea]

Engineering wise it is going to be large.

A large steel beam, a thick wall and something like a railway track to step over.

It won't look like the picture, more like a Peugeot 309 sunroof.

[andyscotland]

The airtightness might be solvable if you took your airtightness layer round the inside of the outer skin to a post at the corner of the door pocket, then made the outer edge of the door an L shape that could be pulled tight against a compression seal on that post. That would probably have to be assembled in situ to get a good seal. So less pocket door, more sliders with a false wall inside to hide them. Could be a pain for maintenance though, and a lot of detail to get right on the build.

 

I never like using the word "impossible" as there is always a way to solve a problem, and in my experience it can seem lazy & undermine trust. If we can build bridges across the sea, we can put big sliding windows in a house.

 

I prefer to say something like "It'll be very challenging to achieve that, off the top of my head I can think of X,Y and Z but there may be other issues too. I'd be happy to look at how we could make it work if you have the budget for me to spend time on that. But from experience I think it's very unlikely you'll want to pursue this when you see the cost and compromises involved, so my recommendation would be that it's not worth spending money on."

 

It's more words, but it's more honest, and it leaves the client in control of their own value judgements. On occasion they have taken me up on it. And once, to my surprise, they saw the detailed costings and went ahead anyway!

 

[JohnMo]

Several issues, other than mentioned.

 

How would you close opening in wall when sliding doors are closed, you need to stop vermin and insects getting in.  Assuming each panel is 75m thick the opening could be 150 to 225mm deep.

 

How do you tie the external skin to the internal one?

 

You would need to add an additional depth to that wall, as above, may start to look strange.

 

Other than that sounds great, but expensive, and full of issues.

 

 

[ProDave]

I think the example in the photo works, because it is just 2 doors, and one slides each way, meaning just one door sliding into a pocket.  There is it much easier for that one door to seal to the pocket both open and shut.

 

I also note in that picture the bottom storey of that wall gets thicker than the upper storey, presumably to give a wider cavity for the pocket.

 

If you could compromise and have your door as just two, that would be a better way to think of it, but your right hand section of solid wall would need to be wider to accommodate a pane sliding in there  (effectively meaning you doors would be narrower), and one very long steel to span that larger opening width.

 

 

[SteamyTea]

It should be possible to, in effect, make a freestanding sliding door. This would be mechanically fixed to, but not structurally part of, the wall.

Then clad/cover to make the pockets.

@craig may know how to do something like this.

 

There are some cars  original Merc S class, that had electric windows, that were double glazed, that slid into pockets in the doors. They could survive and work reliably, at 155 MPH, and bouncing down a rutted road.

Edited June 7, 2022 by SteamyTea

[Russell griffiths]

I have had a triple sliding door, they are monumentally thick, I cannot remember how thick but I think 200mm plus. 

Its a hard thing finding an image of the internet as most are in foreign countries and not to the same spec. 

You will find dozens of pics of triple sliders but most will be single glazed. 

When you add in the size of double and triple glazing you start getting some serious thickness. 

Trying to hide that in the wall will be a serious job. 

 

 

[craig]

18 minutes ago, SteamyTea said:

@craig may know how to do something like this.

 

No, they aren't impossible, however. 

 

You need to have the relevant wall depth available to accommodate them and you need to have the relevant wall width to accept the sliding door sashes sliding inside the wall. For example, a 2m sliding section, will require a length of wall in excess of 2m to accommodate. It's not something we have actually done "yet" but not because of not wanting to, It's a standard system from our supplier.

[craig]

3 hours ago, thefoxesmaltings said:

Each pane is approx 1980mm and the width of the wall for them to slide into is approx 2400mm. I had planned for the 3 panes to slide from right to left. It seems like we have enough space to house the doors within the wall?

 

Sounds good in theory, but you don't have the wall depth. The actual depth of a triple track system is circa 250mm, so if you have a wall depth of 350mm for example you have 100mm for structure and finishes and insulation. Your slider would in effect be 4 leafs at 1980, as it needs the space within the wall of the relevant depth. The triple track option isn't feasible to be completely honest.

 

Start looking at a compromise.

Edited June 7, 2022 by craig

[SteamyTea]

5 minutes ago, craig said:

Start looking at a compromise

VR headsets.

[thefoxesmaltings]

31 minutes ago, Russell griffiths said:

I have had a triple sliding door, they are monumentally thick, I cannot remember how thick but I think 200mm plus. 

Its a hard thing finding an image of the internet as most are in foreign countries and not to the same spec. 

You will find dozens of pics of triple sliders but most will be single glazed. 

When you add in the size of double and triple glazing you start getting some serious thickness. 

Trying to hide that in the wall will be a serious job. 

 

 

 

20 minutes ago, craig said:

 

Sounds good in theory, but you don't have the wall depth. The actual depth of a triple track system is circa 250mm, so if you have a wall depth of 350mm for example you have 100mm for structure and finishes and insulation. Your slider would in effect be 4 leafs at 1980, as it needs the space within the wall of the relevant depth. The triple track option isn't feasible to be completely honest.

 

Start looking at a compromise.

What about reducing the thickness of the timber frame, in that section from 140mm to say 100mm, insulating that, putting something like marine ply and then the pocket door tracks sliding behind all of that? Might end up with a thicker wall on the LHS to accommodate the extra depth of the triple track, but seems like it could work?

Current External wall:

 

[craig]

If you're wanting a triple track pocket sliding door solution, it needs a lot of work and space this is the head (top) detail for Solarlux Cero III - it's 303mm in total depth. 

 

 

You only have the space for one sliding section within the wall.

 

 

71mm is the sliding section within the wall.

 

Edited June 7, 2022 by craig

[craig]

Sorry, I should have added that I would strongly advise against what you're wanting. It will cost a fortune, it will need a lot of compromises (thermally) and is fraught with problems.

[SteamyTea]

31 minutes ago, craig said:

head (top) detail for Solarlux Cero III - it's 303mm in total depth. 

Is that because it is aluminium extrusion?

Taking a leaf out if SpaceX book, stainless steel would be stronger and lighter than aluminium, or CRF for that matter, and I think it conducts less heat.

[craig]

17 minutes ago, SteamyTea said:

Is that because it is aluminium extrusion?

Basically it’s what’s required to deal with three tracks. 

[Mr Punter]

Have a look at ID Systems.  They do a narrower profile triple track pocket door.  They are well thought of and specialise in this type of thing.

[thefoxesmaltings]

Quick update after speaking with Glideline, specifically about a 3 pane sliding pocket, so thought I would share and update the thread...

 

Apparently, it would be fine to fit a 3 pane sliding pocket door into that space and nothing will change structurally from the build.

 

The outer skin brickwork, cavity, timber frame wall is all on the outside and the pocket frame door is on the inside and set back from that.

 

For example, in an external timber frame wall section, rather than 140mm timber frame, reduce that to 100mm. Insulate that and put something like marine ply. The pocket door and tracks slide behind all of that. An additional stud wall is built on the inside which hides and forms the pocket which houses the panes of glass. All doors operate on the inside of the inner skin, so there shouldn’t be a break in the thermal envelope.

 

With a triple track being approx. 210mm, it’s inevitable that I'd lose a bit of internal space as the wall thickness will be slightly greater, but reducing the thickness of the timber frame on the outside, and removing the insulated plasterboard for the wall section, would accommodate and help limit how much that wall encroaches into the living area.

 

I wouldn’t even need to run additional steel into the wall to support the pocket door as it’s not bearing any weight. (To be confirmed by structural engineer of course). Meaning the only additional construction cost for this is for the extra pocket track and studwork.

 

One of the concerns (rightly so) raised above was that when the sliding doors are closed, I would we see a huge 210mm gap on the side of the wall, but the glazing company said that there is a pocket plate which goes onto the interlock covering that up. When the doors are slid, the plate moves with the door, thus sealing the gap.

Edited June 7, 2022 by thefoxesmaltings

[ProDave]

3 hours ago, thefoxesmaltings said:

Quick update after speaking with Glideline, specifically about a 3 pane sliding pocket, so thought I would share and update the thread...

 

Apparently, it would be fine to fit a 3 pane sliding pocket door into that space and nothing will change structurally from the build.

 

The outer skin brickwork, cavity, timber frame wall is all on the outside and the pocket frame door is on the inside and set back from that.

 

For example, in an external timber frame wall section, rather than 140mm timber frame, reduce that to 100mm. Insulate that and put something like marine ply. The pocket door and tracks slide behind all of that. An additional stud wall is built on the inside which hides and forms the pocket which houses the panes of glass. All doors operate on the inside of the inner skin, so there shouldn’t be a break in the thermal envelope.

 

With a triple track being approx. 210mm, it’s inevitable that I'd lose a bit of internal space as the wall thickness will be slightly greater, but reducing the thickness of the timber frame on the outside, and removing the insulated plasterboard for the wall section, would accommodate and help limit how much that wall encroaches into the living area.

 

I wouldn’t even need to run additional steel into the wall to support the pocket door as it’s not bearing any weight. (To be confirmed by structural engineer of course). Meaning the only additional construction cost for this is for the extra pocket track and studwork.

 

One of the concerns (rightly so) raised above was that when the sliding doors are closed, I would we see a huge 210mm gap on the side of the wall, but the glazing company said that there is a pocket plate which goes onto the interlock covering that up. When the doors are slid, the plate moves with the door, thus sealing the gap.

Thanks for that.  That looks possible.  I will be interested in the cost.

 

Remember that word I mentioned, Compromise?  the compromise here is thinner insulation in that bit of timber frame and ditching the insulated plasterboard.

[craig]

So basically not a pocket slider within the existing wall structure but on the inside wall and new stud wall built to enclose it within. A compromise.

Edited June 7, 2022 by craig

[Jenki]

Excuse the poor cut and pace job, but I still see issues with Air tightness.  At the sides of the doors where the pocket is, when the doors are closed there will be a gap internal and external into the pocket void? maybe "sealed" with brushes, and wipe seals? but not air tight.

You will also have 2x width of sash opening internally waiting to accommodate the opened doors? what do you do with that space?

[MikeSharp01]

Looks to me like you need to go for air tightness on the outside pane of the on the left when closed - that should be possible but will depend on the window design - perhaps something like sketch