Ontario Science Museum Roof

[GregLocock]

They used Reinforced Autoclaved Aerated Concrete to build large parts of the roof. Water ingress damages RAAC. Water is often present on roofs.

https://www.cbc.ca/news/canada/toronto/ontario-science-centre-closing-roof-1.7242810

Odd how this huge problem comes up just as they want to repurpose the site.

Here's the technical reports

https://www.infrastructureontario.ca/en/news-and-media/third-party-reports/

The Building C report describes RAAC in some detail.





Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[SWComposites]

Water is often present on roofs, wow, who would have thought that?

 

[GregLocock]

I'm guessing that the new wonder-material wasn't tested for long in real conditions before being deployed worldwide. The 1960s fashion for flat roofs is part of the problem.

Here's an expert

https://www.lboro.ac.uk/news-events/news/2023/march/reinforced-autoclaved-aerated--concrete-raac/

Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[MintJulep]

Odd how this huge problem comes up just as they want to repurpose the site.

Not really.

Old building, old purpose, old owner/tenant. Dumb fat and happy syndrome - no incentive to look at the asset too closely.

Potential new purpose with new owner or tenant triggered some sort of independent due diligence that found the problems.

 

[hokie66]

Water is supposed to be repelled by the roofing, so the roof structure is protected. This whole saga may not be due to the inherent properties of the AAC materials, but rather to lack of maintenance of the roofing.

 

[zeusfaber]

Been big news in the UK over the last year or so. Lots of school buildings closed in a hurry while they work out how likely the RAAC is to stay in place.

 

[Alistair_Heaton]

I used it on my building in the hobbies forum.

I used it for the floor.

It is in the main a maintenance issue. Also is ability to offload moisture by breathing. You also need to plan your thermal gradient and moisture movement vector.

The older buildings getting internally redecorated with none moisture transport cladding seems to be a big issue. The aerated just loads up with water which it can hold over 70% by weight of the base materials with no visual indication.

The reinforcement corrosion can occur in less than a year with a roof leak to a compromised structural state.

 

[drawoh]

From the Toronto Star, I led the Ontario Science Centre for five years. This is the real reason it’s time to let go of the old building. This backs up MintJulep.

There is a joke in architecture that is the roof doesn't leak, you weren't trying.

--
JHG