Fitting large sliding patio doors to a steel frame

[liftfan]

Hello,

What's the best way of fitting a triple track sliding door to a steel sway frame? I want to minimise thermal bridging.

I'm building my own extension and have Building Control approved plans including those from the Structural Engineer.


I currently have this:

Designed this:

and I've started "building" in Sketchup:

For the jambs the detail they've supplied is this:

As the triple track is so wide they don't just fix into the outer block. Due to my steel frame I was thinking of just using a 50x200mm timber fixed to the steel to close the cavity with a DPC against the outer block:

Would that work?


Thanks!

 

[liftfan]

Same with the head.

The detail supplied by the door company is this:

But the Structural Engineer specified a separate galvanised angle lintel.

Again, could I just bridge the cavity with timber?

 

[liftfan]

Apparently, having timber in the cavity is no good so I should use structural foam such as Compacfoam instead. I was thinking of fixing a 4x2 timber to the steel as shown below.

Anyone done this?

 

[liftfan]

Speaking to a sliding door company they say fixing to steel or timber is ok. They said speak to your builder. Unfortunately, that's me!


So, should I fix a 4X2" timber all around the steel or not?

I'm thinking it would help with thermal bridging and fixing plasterboard.

 

[Dodgyrog]

Bit of a longshot but what about the general concept of doubling up that outer skin? I appreciate you might be dealing with an existing build so not quite sure what is practical and whether that is existing or new steelwork - but then you could hang everything off the thicker outer skin? I'm a DIY'er though so have no idea if its allowed / practical or not

 

[liftfan]

Thanks for the reply. I've done the concrete trench fill but that's all so far. The steel is as specified by the structural engineer so I can't change that, give or take a few cm. The design with Building Regs approval is for a cavity wall with the side returns supported on lintels to span the existing retaining wall. So thanks for the suggestion but I'm tied to the existing plan.

The next stage is to order the steel which is why I want to get the dimensions right.

I suppose my real question is what do builders do to avoid thermal bridging when dealing with steel frames?

 

[Dodgyrog]

Thanks for the reply. I've done the concrete trench fill but that's all so far. The steel is as specified by the structural engineer so I can't change that, give or take a few cm. The design with Building Regs approval is for a cavity wall with the side returns supported on lintels to span the existing retaining wall. So thanks for the suggestion but I'm tied to the existing plan.

The next stage is to order the steel which is why I want to get the dimensions right.

I suppose my real question is what do builders do to avoid thermal bridging when dealing with steel frames?

Got ya - although what I had in my head was effectively just adding the extra thickness to the external side of the outer skin only - so the same concept of using double thick blocks on just the section where the doors meet blockwork if that makes sense - and therefore leaving the rest of the design as is. So only steelwork tweak is the front plate increasing in length as per below - and then your door shifts forward. You've filled the trench though so may or may not limit if you can have a course running down on to the edge of it,

I am doing very similar to you right now steel-work wise and asked the cold bridge question on here with advice being to use 32mm insulated plasterboard on that inner wall. This thread here -

Insulating steel uprights and beam.

Greatly appreciate the ongoing help from here. As per below details we're soon to be installing steelwork consisting of 2 x outer I-Beam uprights (C1) then 2 inner 80mm square section windposts (WP1) which then all support a cross beam with welded plate (to support inner and outer leaves above...

www.diynot.com

Not got to that stage just yet, hopefully in a couple of weeks time.

 

[liftfan]

Thanks for the reply. I've looked at your other threads and it's been really helpful to me.


I'm thinking your suggestion above still leaves a cold bridge as shown by the blue line below. The exposed lintel will draw in the cold from outside and through the frame. The green arrow in the picture points to the thermal break in the frame but as you can see it doesn't work here. However, I think this is how most installations happen but it seems wrong to me.

My structural engineer specified a separate lintel (galvanised). He said the usual welded plate design suffers from corrosion and thermal bridging.

I've added the timber around the sway frame to help it even more . The sway frame is bolted to the footings so that's another pathway so the that's why I had the timber idea. Then add insulated plasterboard and fireboard internally.

Having never built a steel frame before I'm just guessing!

 

[liftfan]

Just to update, here's what I did.

Built the steel frame and lined it with 4 by 2 timber fixed with M8 bolts with DPC between timber and steel. Fixed compacfoam to the timber with timberlok screws (I later added a third screw per length of compacfoam):

I then put the rafters on because I was bored of getting wet as it didn't stop raining for months:

Built the side walls:

Then lifted the galvanised external lintel in place with my trusty electric winch attached to an acrow:

Made a triangle of timber with the rafters to ensure that lintel was staying put:

Came up with a way of minimising cold bridging at the threshold:

Sliding doors went in. The one thing I didn't do myself. The fitters were very happy with the compacfoam and had used it before. Solid fixing.

Inside has been a major bit of work but that's another story.