Rendering over Steel I-Beam

[Spinny]

New bifolds are top hung and fixed into a steel I-Beam across the opening in the outer leaf. So the edge of the steel is level with the face of the concrete blockwork, but there is a deeper web in the steel to be covered over.

 

Architects drawing says fix a render board over the steel and then 'thin coat' render whatever that might be. Someone quoting has said fix render board over and then render over but the finished render will end up quite thick over the concrete blocks to match the render board. So rather than 20mm thick finished render, would end up about 32mm thick. I am not sure how this is going to look where the base of the render ends at DPC level - might look odd ? 

 

Is this usual way to do it, and what is the 'thin coat' render and is that a better answer ?

 

(Also should something be used to infill the web of the steel, such as timber or insulation and how should this be fixed in place. I can see the possibility of wanting to drill and plug the wall for fixings - e.g. for an awning, camera, etc, so leaving the web open and hollow behind the render doesn't seem ideal)

[JohnMo]

Drawing may help explain a little better

[Iceverge]

Our builder used timber bolted to the steel, cement board screwed to the timber and rendered over with sand and cement to match the render on the blockwork. 

 

Wish I'd insisted on using concrete lintels now. I'm not keen on having timber buried in the outer leaf of the house and there'll inevitably be some voids in there which means that moisture may be able to corroded the steel. 

 

Ideally I would like steel:

 

1. Completely encased in concrete for rust protection or

2. Under/behind some insulation to keep it warm and ensure no moisture condensates on it to start with.....

 

 

What I would do in your case. 

 

1. Tac weld or drill and fix some heavily expanded metal mesh to the web of the steel. 

 

2. Fill the web of the steel with concrete entirely. May require some partial shuttering and then poking with a trowel but it's not rocket science. 

 

3. Apply more expanded metal mesh over the whole lot. Use some self drilling screws underneath to secure to the bottom. Better still tac weld the mesh directly to the steel, (you'll need a MIG welder for half an HR). Let the mesh overlap well onto the blocks too to prevent cracking and fix it with a few screws. 

 

4. This will leave a flush and well keyed surface to directly take a coat of sand and cement render. 

 

Following this process you will have 

 

1. Steel complete encased in concrete. 

2. Thermally uniform substrate for the render to avoid differential heating and cracking. 

 

 

 

 

 

 

 

 

[nod]

Your Architect is correct 

Clad it with render board Then use a mesh and thin coat render 5-8 mil buildup 

[Gus Potter]

9 hours ago, JohnMo said:

Drawing may help explain a little better

This sounds tricky! To add complexity often a crack will develop in the render / finish at each end of the beam as you transition to a different material. The detail of this needs a lot of thought!

[saveasteading]

Do you mean that there is a recess in the face of the wall, between the e flanges of the steel?

It shouldn't bd a corrosion problem unless very wet for some reason. But it's v easy to paint in bitumen or oxide anway.

Then the posh solution is metal angles screwd to the steel to support cement board. The other way is simply tanalised stud instead of metal OR even simply wedged in place...Nice and solid.

My choice is bitumen  then galvanised angle. 

 

[Gus Potter]

6 minutes ago, saveasteading said:

My choice is bitumen  then galvanised angle. 

50 years expererience talking here from @saveasteading, not to be disregarded.

Edited Sunday at 00:01 by Gus Potter