Wall cavity arrangement under Large Aperture Sliding Door Track

[GoodDIYjob]

My designs, as critiqued on here regarding flat roof / false pitch design, are light on detail.

In the design it is shown that cavity closers used for windows and doors including at the base of the large sliding doors. Approx 4.2M aperture.

The builder who has just started, said often that they fill the cavity to the top, no closer, beneath bifold and sliding doors, to allow the door track to sit on.

Having phoned the door installers he said he preferred "full fill" of the cavity. Otherwise the back of the door track will be resting on the cavity closer spanning the cavity and there will be nothing to fix the back of the track to and the door will be unsupported underneath, for much of it's depth..... He said cavity closers won't work underneath it.

So, what do people generally do in these cases? I can see their point but the cold bridge is an issue? The door installer says you can put run insulation on the inside of the inner leaf in the area, but the leafs are still bridged until behind where the door is installed!

We are also having underfloor heating, as a part of this, so there would be thin perimeter insulation on the outside of the screed / inner leaf surface anyway but perhaps something more substantial is required or a better solution.

Having searched some old threads on here, I've seen another suggestion to remove (or not build up) the inner leaf blockwork underneath the door aperture and take the slab, 100mm insulation and sand and cement screed right up to the outer leaf? Then the door track sits on that?

Lot of weight in doors - > 300kg but spread out over track width and depth I suppose and also supported from side fixings as well. On the side fixings as well the window installer suggested maybe turning some blocks to provide fixings points but this then cuts into or segments the cavity closer to the reveals....

Very grateful for pragmatic workable suggestions of what solution is used most effectively in practice?

 

[Notch7]

I get our builder to reduce the cavity width down to 30-50mm at door openings and stop the inner leaf at oversite level, then run the floor insulation and screed to the inner face of brickwork.

You could the same, or you bring the inner leaf up to dpc, set the doors back a bit further so the threshold covers the inner leaf. Add your expansion foam as normal.

If the dimensions dont work out, you could lay engineering bricks on edge across the door opening width for the inner skin -that would give you a solid base for the threshold but reduce the inner skin to 65mm.

I prefer to keep a cavity under the doors even if its just say 30mm or so -that way any water ingress cant get inside to the screed layer.

 

[GoodDIYjob]

I get our builder to reduce the cavity width down to 30-50mm at door openings and stop the inner leaf at oversite level, then run the floor insulation and screed to the inner face of brickwork.

Thanks for suggestions.

Ok, so that is a variation of what I read in an older Diynot post, so in your suggestion you push the cavity closer to mimimise the unsupported insulation overhang in the cavity? Still relies on fixings for the door track not falling on the 30mm to 50mm cavity width, I suppose? The floor insulation won't bow down in 50mm unsupported cavity span?

or you bring the inner leaf up to dpc, set the doors back a bit further so the threshold covers the inner leaf. Add your expansion foam as normal.

The track for doors is about 180mm wide, along bottom threshold. So could have to come in a long way (say 120mm), if at back needs to be fully supported on inner leaf. Also, depending on fixing locations on bottom track, they could still be in the cavity space. If I am understanding properly....

If the dimensions dont work out, you could lay engineering bricks on edge across the door opening width for the inner skin -that would give you a solid base for the threshold but reduce the inner skin to 65mm.

Do you mean effectively cap off the top of the cavity? With the engineering bricks on their edge so they span the inner and outer leafs beneath, (15mm bearing onto inner leaf). Then the remaining 65mm with a reduced thickness block? So the wall is still cold bridged and damp bridged, but only at the very top, beneath threshold?

I prefer to keep a cavity under the doors even if its just say 30mm or so -that way any water ingress cant get inside to the screed layer.

So, I can safely assume you don't like the idea of filling the cavity with concrete...

Many thanks for suggestions and help.

 

[Notch7]

The track for doors is about 180mm wide,

If that include cill overhang then its not sitting back much over outer leaf.

If its plus cill then maybe its do-able......100mm outer skin + 40mm cavity + 65mm brick on edge would give you 205mm then deduct 25mm set back.

Cavity fill is fine and is a common way to do it. However in an ideal world a cavity wants to go 3 brick courses below dpc, so any water or condensation falls to bottom and does not track in.

Do you mean effectively cap off the top of the cavity? With the engineering bricks on their edge so they span the inner and outer leafs beneath, (15mm bearing onto inner leaf). Then the remaining 65mm with a reduced thickness block? So the wall is still cold bridged and damp bridged, but only at the very top, beneath threshold?

No I was meaning run the top 1 or 2 courses with bricks on their edge but running lengthwise along the wall, so reducing the effective inner wall thickness to 65mm.

You can minimise thermal bridging by putting some celetex up the inside wall so the screed does not touch the wall. As long as its thin, the floor tiles will fine.

 

[GoodDIYjob]

Ok. So I tried to sketch out the arrangements as I understand them and from helpful suggestions.

The conventional arrangement with the cavity closer both my builder and window installer don't think is viable at all, so just a starting reference for me to understand versus other options.

Have I got these generally correct especially positioning of DPM and DPC?

The solid fill, I could insert a slither of say 25mm insulation between the solid fill and use damp proof concrete. Would either be of any benefit?

I haven't drawn up the bricks on end option, as I'm not sure I understand properly or see the benefit. The cavity would still be 100mm. So the gap for trying to mount the base of the doors in potentially unsupported area above the cavity still exists but it has brought the inner course in 35mm. Does that help much. Sorry, I may be being a little slow with that...

My layout options attached.

 

[Benway]

My BCO was happy with 2 runs of 100mm block under my 7.5 door. No inner block.

I'll try and find a picture.

Cheers.

 

[Benway]

Best I could find.

 

[GoodDIYjob]

Thanks for replies. So, the door track is about 180mm excl. a minimalsit 10mm cill overhang on the external. So what we have decided on today, which hopefully solves, is lay a second course of bricks against the outer leaf on their edges. So 100mm outer, 65mm+10mm mortar for bricks on edge beneath doors.

So total solid support for door track and all fixings is 175mm deep from outer leaf outside face . Then a 25mm celotex layer behind to fill the remaining 25mm of the 100mm cavity below. The inner blockwork is to stop at below slab level. so the 100mm floor insulation and part depth of the screen butt up to the thermal break upstand. Slab is under insulation due to UFH.

DPC covering thickness of 175mm outer combined leaf. DPM brought up inside (room internal side) of insualtion.

For something that must come up all the time with doors with 180mm track that needs supporting from underneath, it is surprising how much angst this has caused me so far. I would of thought my retailer and installer of sliding doors would of just had a approved aperture requirement documents for brick / blockwork beneath threshold, that complied with BR, but on requesting, they have no such thing......

Thanks again for comments. I seem to have borrowed a bit from all responmses to get to where I am now....

 

[noseall]

Surely you would set the inner leaf masonry so that you form the door reveal returns back to the door jambs and fill with concrete/screed?