Steel to support a garage door

[puntloos]

My current garage design looks like this:

 

(the 1st floor ends roughly at the words "wall plate" so the weight comes down on that steel. )

 

My question: Currently my house design has 6 steel beams pointing (by necessity) straight down into the foundation, and my understanding is that these constitute a high amount of energy loss. 

My builder says that if we get rid of the number 5 and 6 steels (left and right of the garage), I would have a massively lower amount of energy leaking away. But the downside is that they wouldn't be able to support a full garage door since in particular the corner wall point would not be strong enough. 

 

2 extra steel beams add a considerable amount of energy loss, my builder claims about equal to the amount my first floor altogether loses. 

 

What do? 

[markc]

203x203x46 UC is a substantial column with a massive load bearing capacity, they must be there for something other than supporting a garage door. 
assuming this is a really good, heavily insulated garage door, it is likely to weigh around 300kgs which is nothing compared to the structure and occupancy.

so my feeling is your builder is talking rubbish and omitting two large UC columns is going to affect much more than just being able to have a garage door.

[DevilDamo]

Well, that’s the first time I’ve heard a builder suggesting to remove steels in order to reduce heat loss 🤔 It’s normally to replace them with a concrete lintel (as it’s something they’ve done in all their career spanning over 30 years).

 

There is going to be no benefit in omitting those columns. Structural integrity in this instance is a lot further up the list than thermals.

[Mr Punter]

It is odd that your builder is concerned about heat losses or has any idea where they will occur and to what extent.

 

Your engineer has designed a goalpost structure.  If you take the columns out, what will hold up the crossbar?

 

As an aside, @tonyshouse built a brick and block house with a wide cavity.  Have you looked at the website?  http://tonyshouse.readinguk.org/mitigation-of-thermal-bridging/#more-247

[puntloos]

Well the builder is a passivhaus builder with their own design team and thermal team. They absolutely know what they are talking about in principle.

I do think they sometimes will optimise beyond "reasonable" but as I understand it my house is somewhat close to failing passivhaus spec so indeed a big steel that drains heat into the foundation does sound somewhat problematic if you don't have a buffer anymore.

 

Of course we can have the steel and simply have to heat somewhat more.

 

 

[puntloos]

On 22/11/2022 at 05:32, markc said:

203x203x46 UC is a substantial column with a massive load bearing capacity, they must be there for something other than supporting a garage door. assuming this is a really good, heavily insulated garage door, it is likely to weigh around 300kgs which is nothing compared to the structure and occupancy.

Well I think you're right this is not just for the garage door. The entire house (2 floors) rest on top of these points. 

 

On 22/11/2022 at 05:32, markc said:

so my feeling is your builder is talking rubbish and omitting two large UC columns is going to affect much more than just being able to have a garage door.

 

My understanding is that a vertical beam of steel will conduct a lot of heat into the foundation. Instead, a sufficiently bulky set of bricks can do the same but that's why it was specced to be at least 600 wide and much more insulating.

 

I don't think builder is talking rubbish, the only difficult choice I have to make is if the 1-2% extra heat loss is worth the aesthetics(assymetry), and a few practical points on that assymetry.

[puntloos]

On 23/11/2022 at 09:57, Mr Punter said:

Your engineer has designed a goalpost structure.  If you take the columns out, what will hold up the crossbar?

Well, the brick version of that beam? Surely that is also capable of loadbearing.

 

On 23/11/2022 at 09:57, Mr Punter said:

As an aside, @tonyshouse built a brick and block house with a wide cavity.  Have you looked at the website?  http://tonyshouse.readinguk.org/mitigation-of-thermal-bridging/#more-247

 

Looked at that but I don't see any advice on steel beam mitigation

[DevilDamo]

You’re worried about heat loss through a structural element? I’d be more concerned about the heat loss as a result of potentially poor or not as thorough workmanship via the most common junctions in a house.

[Mr Punter]

Armatherm do lots of thermal break solutions for structural steel.  I think it is expensive.  Do you actually know what the heat losses would be without it?

[puntloos]

6 hours ago, Mr Punter said:

Armatherm do lots of thermal break solutions for structural steel.  I think it is expensive.  Do you actually know what the heat losses would be without it?

That might not be a bad idea. Define expensive, 500 quid per block, so 2500 for 5 vertical steels?

 

[AliG]

You had previously posted this plan which shows the position of the steels better.

 

There is a little cold bridge there.

 

The plan does not show a PIR edge around the upper floor screed. This would make a big difference to the cold bridge there and indeed all around the upper floor as the screed touches the blockwork as shown. They are not shown on the ground floor either, I would assume the builder has added them in if he knows his stuff. I guess the interior upper floor blocks could also have a Marmox block between them and the steel which would also reduce the cold bridge. Finally you could maybe put PIR between the beam and the steel if there is space.

 

The vertical posts should not be a concern as they are not in a heated area. If there is a concern it would be heat getting not the horizontal beam and via that into the posts.

 

 

 

[Mr Punter]

With the flat roof parapet you could leave the inner leaf lower and run the roof insulation straight to the outer leaf and have a narrower parapet.

 

Also run a course of Marmox plus a course of 7N Celcons on the outer leaf on the steel beams to stop them getting cold.

[puntloos]

4 hours ago, Mr Punter said:

With the flat roof parapet you could leave the inner leaf lower

There's no inner leaf though, the flat roof has no parapet - basic idea would be this:

 

4 hours ago, Mr Punter said:

and run the roof insulation straight to the outer leaf and have a narrower parapet.

 

Also run a course of Marmox plus a course of 7N Celcons on the outer leaf on the steel beams to stop them getting cold.

Note you're looking at a slightly older design of the garage section - the idea is to have the thermal envelope of the house start at the inner wall separating garage into bike store(cold) and utility(warm)... 

But yes surrounding the beam seems helpful, it just isn't always possible I think

 

By the way the armatherm seems like a great solution around this. Plus they hired Morgan Freeman to narrate the video https://www.armatherm.co.uk/thermal-bridging-applications/column-base-thermal-bridging-solution/ so it must be true. I just never knew that thermal materials can hold something as heavy as a house. 

 

[puntloos]

(can't edit anymore)

 

@Mr Punter- do you perhaps have a side view of a "course of Marmox plus a course of 7N Celcons on the outer leaf on the steam beams"? How would this work?

[Mr Punter]

Here you go.  Steel beam not visible, course of Marmox, course of 7N Celcons, course of med density agg, lower bit of cavity tray.  The bricks are left out to clear out the cavity tray.  Cavity will have 150mm EPS beads.  Bricks will have a coat of Stormguard.  Probably a course of slate under the Marmox to get the coursing to work.

 

[Gus Potter]

On 22/11/2022 at 03:10, puntloos said:

My current garage design looks like this:

 

On 22/11/2022 at 03:10, puntloos said:

My builder says that if we get rid of the number 5 and 6 steels

Hang on!

 

I may be over thinking but my first reaction is.. the 203 UC columns and beam are probably working to provide part of the horizontal stability stystem to the house. Easily over looked but critical for safety.

 

Can you post more of your plans. Also post if you can the connection design between the column and beam as this will give a clue as to what the columns and beams are intended to do.

 

Please don't swap these out until you check with your SE.