Fixing balustrade to ICF

[Adam2]

I'm looking into the design options for some terraces which will have a frameless glass balustrade. Other aspects of the design are hollowcore planks resting on the ICF wall.  Simple section view below. The blue is the ground floor ICF wall and grey is the hollow core planks. Red is the extension of the ground floor wall taken up to form the low level wall below glass balustrade poured after the hollowcore is installed.

 

I was thinking how to take advantage of the concrete pour to secure the fixings for the balustrade and considered setting some bolts into the concrete or even setting the channel that the glass will sit in into the concrete. I believe setting aluminium channel in concrete would not be a good option (reaction, hydrogen, general badness) - possibly could use different material - stainless steel possibly for channel. Or just forget the whole idea and drill into the concrete and mount channel above or to the side (after stripping out ICF).

 

Appreciate thoughts/experience from others who may have been through the same process.

 

Thanks

 

[Mr Punter]

Most of the systems I have seen you drill into concrete and face fix or fix through the base of the channel. This provides a satisfactory fixing and I imagine this is easier than trying to accurately cast the fixings into the concrete.

 

What is the required finish on the red bit? Is there to be a coping or cill detail for this?

[Adam2]

Coping detail from glass to top of rendered ICF.

Was wondering if channel could just be pushed into concrete immediately after pour to provide a very secure fixing and would be potentially quicker and with less materials though only found aluminium channel so far. I imagine an issue with setting the channel could also be concrete ingress at joints or ends... 

[Mr Punter]

I would not bother trying to cast the channel into the concrete as if it is not spot on it will be difficult to remedy. Also the channel will get filled with all sorts of crud.

 

We have put in some glazing where we used a recessed ali channel but formed the recess out of timber slightly over sized.  We still needed to adjust some bits with a grinder and bolster. Ali trims all round.  Ours slotted into the sides as well because it needed to act as a flood defence.

 

 

Have you worked out floor levels with the insulation, waterproofing and fall required on the terrace v 1st floor floor?

[Adam2]

Thanks, sounds reasonable. 

Architect is working on levels at the moment, as you mentioned lots to factor in, probably using alwitra and their preformed sloping insulation with adjustable legs supporting tiles above 

[Mr Punter]

Cut to falls insulation is expensive. Cheaper to concrete to falls and use normal insulation.

[Adam2]

OK - will see how that could work.  Just looked at cut to fall insulation  - labour on concrete could even it out maybe? I saw xtratherm provide an off the shelf PIR product falling 20mm over 1200. Sounds like could be better than the architect's thoughts on a custom ordered product. Price on that is £91 for 4 sheets 1.2m x 1.2m and I'd need 5 packs so £450 (+ of course the flat insulation to go under) and I'd of course need the insulation anyway.

 

https://www.insulationsuperstore.co.uk/product/xtratherm-tr-mg-tapered-roof-board-5070mm-5-76m2.html?gclid=Cj0KCQjw19DlBRCSARIsAOnfRei5qlgFFPjo2ZiXTMqUn6tLFq4z-VjRi4ErVccQgzgE51KPplO2iYsaAuqtEALw_wcB

 

Just did some calcs on floor (am sure architect and engineer will be looking at this) looks like above the concrete plank inside will be 50mm insulation + 75 screed + 25 tiles so 150mm and the other side probably 150 insulation (sloping to 100mm) + legs for tiles (20-55mm) + tiles 20mm = ~157mm. I think 50mm PIR is specified under concrete plank in the ground floor ceiling). Feels that having the planks at the same level will simplify the plank install + ICF build/pour but will follow up with the professionals to see what the thinking is there and the orientation of the planks which may only come out after engaging the supplier to get the design done.

 

[Mac123]

Hi Adam2, 

 

I hope its ok to bring up an old post.

I'm doing a self build with Amvic ICF, just about to finish roof and have a balustrade detail to figure out. 

 

Would you be able to share the detail you ended up going with in the end?

 

 

[FM2015]

On 15/04/2021 at 00:19, Mac123 said:

Hi Adam2, 

 

I hope its ok to bring up an old post.

I'm doing a self build with Amvic ICF, just about to finish roof and have a balustrade detail to figure out. 

 

Would you be able to share the detail you ended up going with in the end?

 

 

Resin fix post concrete.  Simple

[Adam2]

On 15/04/2021 at 00:19, Mac123 said:

Would you be able to share the detail you ended up going with in the end?

We're likely to go with side fixings on the inside face of the parapet wall on the terrace. Will strip the ICF down to the roof slab and bring edpm up the face of the concrete and over the top with some magic water tight fixings through this into the concrete.

 

[Mac123]

Hi guys,

 

thanks for the replies. I only seen the response now. 

I'm still looking for a good thermal break free solution, unfortunately the concrete has been poured already as in the pic below.

So as I see it there is a thermal cold bridge coming through on the concrete down into the hollocore ceiling as in the red line on the picture below.

 

I am thinking on putting insulation on top of the parapet wall now and somehow fixing into the side where the green lines are in the drawing.

I have contacted quite a few glass balustrade companies, my engineer etc, but none are quite giving me the answers I want to hear. 

 

In hindsight, I should have put insulation in the blue circle and put rebar up through and poured concrete on top, probably would of been the best solution

 

Any suggestions thoughts on the best remedy?

 

[Mac123]

On 16/04/2021 at 17:07, Adam2 said:

We're likely to go with side fixings on the inside face of the parapet wall on the terrace. Will strip the ICF down to the roof slab and bring edpm up the face of the concrete and over the top with some magic water tight fixings through this into the concrete.

 

 

Magic water tight fixings? What are those then?

[Gus Potter]

7 hours ago, Mac123 said:

Hi guys,

 

thanks for the replies. I only seen the response now. 

I'm still looking for a good thermal break free solution, unfortunately the concrete has been poured already as in the pic below.

So as I see it there is a thermal cold bridge coming through on the concrete down into the hollocore ceiling as in the red line on the picture below.

 

I am thinking on putting insulation on top of the parapet wall now and somehow fixing into the side where the green lines are in the drawing.

I have contacted quite a few glass balustrade companies, my engineer etc, but none are quite giving me the answers I want to hear. 

 

In hindsight, I should have put insulation in the blue circle and put rebar up through and poured concrete on top, probably would of been the best solution

 

Any suggestions thoughts on the best remedy?

 

 

Hi Mac123.

 

Ah, hind sight is part of life and an intrinsic part of the process. It is very rare that as a designer you sit back (cut yourself some slack Mac), look at the finished job, how it looks, how buildable it was and think.. I got that spot on design wise, at the best price and it was so buildable that we have actually got what we wanted from the builder without a barny. There is always room for raising the standard, tweeking the design on reflection.

 

Also design is often about getting the best compromise.

 

"In hindsight, I should have put insulation in the blue circle and put rebar up through and poured concrete on top, probably would of been the best solution"

 

Yes in an ideal world from an insulation point of view but no from a structural point of view as the balustrade is introducing a bending moment into the concrete. My own view is that simplistically as heat rises you'll get more thermal bridging though your telephone wire than the long convoluted thermal path you show.

 

On the upside what you do have is a good concrete core to post (say resin fix to) fix to and this can open up the opportunity to create a cracking clean detail. It looks like you have quite a good thick concrete core. If your budget can stretch to it then you could maybe cap the wall with a stainless steel plate with intergral drip detail, make the welding a feature. Use counter sunk hex bolts in sleeves to give that "engineered look" for the cap plate. In principle I think this could work but have not done a fag packet calc as yet.

 

The cap plate fixings would be taking a bending force so you need to know a little more about the concrete, thickness and so on. By a clean detail I aslo mean something that looks great Architectutally but also something that is easy to maintain and keep clean.. not gather mould etc. Think about the welding on a motor bike frame, it can be a work of art, no sharp corners to gather dirt.

 

I think with a bit of thought you could do something pretty tidy here. One of the keys is always to check any corner weathering details before you get carried away.

 

Your starting point here is to look at the glazing / glazing fixings you want, post some dimensioned details here and you may get a few ideas on how you it make work from an SE point of view. Once you have that it may be that all the weathing detail falls into place in a simple way. In some ways I'm suggesting you spend more on the balustrade as you see this and less on what is covered.

 

Part of my thought process is driven as I can see that the side plate on your drawing has a much reduced concrete fixing edge distance and the fixing spacing looks questionable. That may be a reason why you're not getting the answers you want SE wise. Also getting all this lined up, and interfacing with the upstand membrane looks problematic.

 

 

 

 

 

 

 

 

 

 

 

 

[Adam2]

On 23/04/2021 at 12:43, Mac123 said:

Magic water tight fixings? What are those then?

 

Just large rubber or neoprene washers around the bold securing the U channel to the balustrade - I think also with a waterproof mastic or something around the bolts.

 

Your image looks like bolts (pairs? our are single bolts) are near the top of the concrete. I think we needed to leave 50mm from edge of concrete. You may also need to strip the EPS to fix directly to the concrete (more cold bridging I know, unless you do something around the U channel after. Oy you could look at the stand-off fixings, ours are quite exposed so not so keen but in a more sheltered location maybe could work OK.

 

If you side fix, could you put EPS on top of the parapet wall with a capping over this? May also need timber on the EPS for capping connections?

[Mac123]

Cool, Thanks for that Adam. 

 

Looks like I am going like the attached detail now, sizes etc are not exact but I'm sure you get the gist of it. 

I'll probably use you rubber/neoprense idea around the bolts securing the U channel along with waterproof silicon etc

maybe even a dpc coarse on top of ply under channel, can't hurt either, every layer helps  

 

 

[Adam2]

I guess your metal trim will be above  the membrane? May be an idea to return the membrane down behind the trim and fix to the wall else this could be a path for water - unless you're planning to render up behind the trim or seal in some other way.

 

Maybe good to check with your SE or balustrade supplier on the use of EPS in that position. 

 

From my waterproofing co the issue they see with top mounted balustrade is that you need to consider how water will drain from the U channel, maybe your channel has drainage holes on the vertical sides?