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Any ideas why concrete would be poured between some joists?

ULMarc

Hello,

I've these 3 joists in my house which have concrete between them. You can see in the picture attached. There's a porch that overhangs the front of the house. So the area you're looking at here is overhanging that porch. Though, note the porch is the length of the house so the joists without concrete are also overhanging it. This is the only location in the entire structure with concrete between the joists like this.

The concrete doesn't extend the entire span of the joist, it's only what's shown here in the picture and about another meter.

Does anyone have an idea what the intended purpose could be?

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C. Eastwood

https://www.boards.ie/discussion/2058252985/any-ideas-why-concrete-would-be-poured-between-some-joists

What is immediately below the concrete.

ULMarc

The ceiling of the porch is directly below it, shown in this picture. The centre joist in my first picture travels above the right hand side of this door and this column shown here.

I thought perhaps it was put there in the past to accommodate some feature above the door. But it's not over the door. There are a total of 4 columns supporting this porch. There's no poured concrete at any other location but this one.

C. Eastwood

https://www.boards.ie/discussion/comment/119288503#Comment_119288503

I have never seen anything like this. I cannot figure out what the concrete is for.

Each of the 2 slaps of concrete as seen would be approx 50 kg each.

There appears to be no ceiling slabs below the ceiling joists to the right hand side of the concrete in the top photo.

There doesn’t appear to be any Attic Insulation

Victor

Cue someone getting a big surprise when it crashes to the ground after a wet winter 26 years later - at 3am.

Might the roof have been re-modelled at some stage?

Is it a detached house? Might this have been fire proofing / security?

ULMarc

https://www.boards.ie/discussion/comment/119290405#Comment_119290405

I really don't know to be honest. It baffles me. I really hope it wasn't some attempt at mitigating some structural damage to the encased joists.

It's a house on it's own.

ULMarc

https://www.boards.ie/discussion/comment/119290351#Comment_119290351

What you're looking at is the area over the outdoor porch. So there's no ceiling to slab I suppose. And no sense insulating the cold outside from the cold attic.

But, apart from that, the house does have a pathetic amount of insulation that we're in the process of rectifying. This random slab of concrete is in the path of both insulation and rewiring jobs. I'd love to knock it out. But always like understanding the thinking behind something before going Rambo on it.

muffler

Whats the story with the house..are you first owner or when did you buy? When was the house built and were there any previous renovations carried out? If you bought did you get all relevant certs?

asdfg87

Have you owned the house from new, it looks like there was somethinh like a chimney removes and replaced by a colm, the concrete likely be a way of replacing and transferring weight to pillar, looks like a good job.

ZX7R

https://www.boards.ie/discussion/comment/119290351#Comment_119290351

I have seen it before it was in houses built in the 60s early 70s.

It was used as a form of ballsed over large porched areas usually over the front entrance..

Victor

https://www.boards.ie/discussion/comment/119290853#Comment_119290853

Ballast?

ZX7R

https://www.boards.ie/discussion/comment/119290888#Comment_119290888

Basically they added it for extra weight as support for the roof due to the open area underneath. In case of wind

It was a old way of doing it.

Victor

https://www.boards.ie/discussion/comment/119290936#Comment_119290936

Sorry, autocorrect ate the word "ballast" on you. 😀

ZX7R

https://www.boards.ie/discussion/comment/119290997#Comment_119290997

I'm not great at spelling at the best of times 👍,autocorrect can be a nightmare for me🤣

ULMarc

https://www.boards.ie/discussion/comment/119290936#Comment_119290936

The porch extends the front of the house, it's about 13 meters wide. There's probably 40 or 50 joists in it. Would it make sense it's only in this one very local area? Would you be able go to into more detail of the new way of doing it?

It's a 1960s house for others asking. I'm just the new owner. I have engineers and various other reports pre-purchase. But I don't have any certs for, whatever this is 😁. If it's even certifiable 🤣

ZX7R

https://www.boards.ie/discussion/comment/119291305#Comment_119291305

It would have been to code at time of construction.

Many ways how the do it know.

You could have a concrete plint with the pillar attached and metal wired baskets filled with rock as weight placed around it.

You could deep bore a hole and place a priest cast pillar.

Or use rsj .

Many ways to do it now a day's

ULMarc

https://www.boards.ie/discussion/comment/119292040#Comment_119292040

So, to explore this I've put together this sketch of what the structure of the area is like. The components of the image are as follows:

The blockwork wall is the exterior wall of the house.
The yellow brick column is 1 of the 4 columns supporting roof at the front of the house.
The other yellow objects are roof joists and rafters.
The silver span is the RSJ's spanning the front of the house.
The 2 dark grey objects are the concrete elements we're talking about.

I notice that the concrete spans from the RSJ to the wall plate. If, as you say it is ballast, then I imagine it's intended to rest atop the RSJ. And the reason for the length of the concrete forms is to span to the exterior wall. Such that it's supported at both ends, by the RSJ and the wall.

Now, there are 4 columns in total at the front of the house supporting these spans of RSJ's. Underneath these concrete forms I'm uncertain if the RSJ is continuous. Though, I imagine it's not as I can see at the other column there is a plate joining 2 RSJs.

So, I wonder, why could it be that this is the only location on the entire roof that has ballast by design?

ZX7R

No idea why they put it just in one spot and not another to be honest,

ULMarc

https://www.boards.ie/discussion/comment/119293108#Comment_119293108

It's staying put is the long and short of it anyway. :)

I just need to figure out the most practical way to route cables around it now. It's blocking an ideal route.

The Continental Op

So, I wonder, why could it be that this is the only location on the entire roof that has ballast by design?

Any chance the "ballast" is on the side nearest the direction of prevailing wind?

Crocodile Booze

Interesting outdated structural feature alright. Never seen it in any of the many roof spaces I've been in. It's unlikely to shift at this stage but what exactly is directly attached underneath it - looks like timber cladding? It's probably reinforced and supported at both ends like a lintel?

ULMarc

https://www.boards.ie/discussion/comment/119294206#Comment_119294206

You know, I don't know where the wind prevails from. But, again, it's the only one on that side. Still making it an oddity.

ULMarc

https://www.boards.ie/discussion/comment/119294374#Comment_119294374

That is just timber cladding alright. There's no evidence of anything else between the cladding and the slab. Yeah, the slab looks to be supported on both ends, one end by column and RSJ, the other by the exterior wall of the house.

The upstairs structure of the house is a dormer. So there's this wooden substructure upstairs. This slab happens to be under one corner of that structure. But I don't think it's any relation. Again, it remains the only instance of it in the entire building. Making me remain curious why it's necessitated here.

I really wanted to rip it out when I saw it. Thinking it was just some atrocity of a deign feature for the porch below. Maybe I've a portcullis?! But seeing as it's anchoring my house to the ground and preventing it from flying away it just might have to stay.

The Continental Op

Wind blows most frequently from the south and west for open sites ....

https://www.met.ie/climate/what-we-measure/wind

So my guess is that pillar nearest the corner that faces West and South?

ULMarc

https://www.boards.ie/discussion/comment/119294970#Comment_119294970

Maybe yeah. the front of the house is facing south west. This pillar is on the southernly side of that.

what_traffic

The 4 pillar columns are just brick column's? The roof is resting on them.

If these columns were re-enforced steel poured concrete columns then it would be a different structure and would not need this ballast slab.

I would leave it be, its done its job to date. The roof has survived a fair few storms since this ballast slab was installed.

You said you have an Engineers Report of the house pre-purchase. I am amazed that they missed this?

I would call them up and get them to have a look at it again if there is nothing in the report. It seems a very basic feature to miss and you should not be charged for it.

Still stihl waters 3

https://www.boards.ie/discussion/comment/119296817#Comment_119296817

If there's nothing in the report maybe they didn't charge for it

ULMarc

https://www.boards.ie/discussion/comment/119296871#Comment_119296871

I think he means that if I were to check in with my engineers now, after the fact, they might be understanding and assess the structural element as a point of goodwill / professional duty.

Still stihl waters 3

https://www.boards.ie/discussion/comment/119297579#Comment_119297579

Oh I see, my bad.

what_traffic

https://www.boards.ie/discussion/comment/119297579#Comment_119297579

Ya thats what I meant, I didn't word it well.