Sliding door track over cavity

[Ashdown]

We are using sliding doors (Reynaers CP130) fitted into traditional cavity walls - 100mm brick, 100mm full-fill PIR, 100mm blockwork. The challenge is to adequately support the track which will largely end up over the cavity. The aluminium track has a plastic thermal break meaning it has little lateral strength and cannot bridge the cavity and carry glass up to 200Kgs without a substantial substrate beneath. 

 

Ideas have included mass-filling the cavity with concrete and steel plates across the cavity. However these will both provide significant thermal bridging. 

 

A solution we are currently looking at will be to fill the cavity under the track with Leca Insufil and compact by light hand-ramming  (it will compact by around 10%). Above this a layer of CF board (Purenit) 40mm or so.

 

Hopefully this combination will provide a firm base which will have low thermal conductivity and minimal impact from moisture, but we are not familiar with these materials used in this type of application. 

 

Any thoughts please?

Many thanks 

Peter

 

[Temp]

200kg create a force of about 2000N. I looked up the compressive strength of one make of PIR insulation and they claim 140kpa which is 140,000 Newton's per square meter. So you would need to spread the load over at least...

 

2000/240,000 = 0.014 sqm or 140 square cm.

 

Which isn't that much. So I think something rigid over PIR would work. I supect the devil will be in the detail.

 

[Ed Davies]

I think Temp is a bit optimistic. That 140 kPa is presumably the BS EN 826 value (it is for Celotex XR4000) which is for 10% compression. If you have 200 mm of foam under the door you'd be a tad disappointed to find it moving up and down by 20 mm every time you slide it. Also, the weight is obviously important but you've also got to consider the forces as the door moves, the weight of hefty people stepping on the runners as they stagger in and out… I think you'd want it bearing on a minimum of 20 times that area (10x to reduce the compression to 1% then double it for the extra forces).

[jack]

Possibly more expensive, but what about foamglass?

[Russell griffiths]

Have a look on Charlie luxtons new build, he used a fibreglass angle to sit his doors on as they had a smaller thermal bridge than a chunk of steel. 

Or you could look at marmox blocks, which are insulated blocks but with high compression due to some inner epoxy type dowels 

[Ashdown]

Thank you for the useful data - the Leca insufil is a version of the lightweight expanded clay aggregate used under roads and bridges and has a compressive strength of 0.7MPa which we were considering using just in the cavity directly under the door track (PIR elsewhere).  

https://www.leca.co.uk/sites/default/files/DoP_DK_15210000xxx_EN 15732_UK.pdf

 

The Purenit is a very dense PIR product which claims a compressive strength of over 5MPa and shear strength of 1 to 1.5MPa.

http://www.cfsfixings.com/products/purenit

This we are considering fitting across the cavity directly under the track - sketch attached.  

 

One concern is that if the Leca settles, then the Purenit will be asked to bridge the cavity, which is where there will be a combination of shear and compression on the edges. Not being a mechanical engineer I can't really tell what would happen but I expect we may need to try some and test it. It it works though it would be an easy solution for anyone to use.

 

I will go and look up foamglass, fibreglass and marmox!

[Ashdown]

Under sliding door sketch.pdf

[Russell griffiths]

Looking at you sketch, I think you need to include your finished floor, will your floor structure not continue into the door reveal area? 

As it looks are you not creating a straight joint in front of the door, depending on floor finish this could lead to cracking in the finished floor. 

 

I have spent a good good few hours thinking of this detail, mine is icf block and I’m going to install marmox blocks in the inner core and have the floor screed continue into the door reveal to prevent any straight joints. 

[craig]

Big blok cavity closer by cavalok, can’t link to it (i think) but we have recommended to a few builders in the past.

Edited November 18, 2018 by craig

[mvincentd]

https://www.greenbuildingstore.co.uk/products/compacfoam-200/

 

I planned on using this but had enough Marmox left over so went with that.  A 6 metre long course of marmox though doesn't exactly end up dead flat and level so check the requirements/tolerance of your sliders...you may end up needing to top it off anyway with something more flat and smooth like marine ply.

[mvincentd]

On 10/11/2018 at 11:31, Russell griffiths said:

I’m going to install marmox blocks in the inner core

Im sure in practice your marmox will work as shown but just to check you're aware you cant build in multiple courses with them.

[Russell griffiths]

I sent my details to marmox and they we’re happy. 

I wouldn’t use ply under a slider for two reasons 

1 it could get wet and rot 

2 it will compress

i think somebody on here already did this and found they have a dip in their bottom track

[craig]

Sliders need a solid base to sit on, have you considered Purenit over Ply?

Edited November 21, 2018 by craig

[LeeVanCleef]

@Ashdown are the sliding doors in yet Ashdown? Any feedback on them? Looking at them for an upcoming project

[Ashdown]

Had a delay on this project for all sorts of reasons so the doors are not in yet. The door company is going to supply Purenit which at 40mm thick is going to take the load and span the cavity but I am a little concerned about cracking in the floor as raised by Russell earlier. I will try and upload the dwg later.