reinforced concrete flat roof

Postby tcplumbing » Sun Feb 01, 2009 5:13 pm

Hi All...
Any help appreciated here on this one!
Our house is approx 70 yrs old and has several brick built out houses,
These are all covered with a 5 inch thick concrete roof which has metal reinforcing rods running through it (Latticed)

These have begun to corrode over the years and have started to burst the concrete roof from underneath thus allowing water through.

Does anyone know if this can be repaird in ayway... ie, Inhibit further corrosion and repair the concrete? Or is it a case of removal and replace with conventional roof?

Many thanks.

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Online roofing products and solutions

Postby youasked » Wed Mar 25, 2009 3:10 pm

Liquid Rubber.... best and can be done inside as well as on top.
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Postby DIYJack » Fri Mar 27, 2009 11:41 am

Hi tcplumbing

I would suggest that in this situation, liquid rubber is not the answer to the underside of the roof. If the reinforcement has corroded resulting in the concrete bursting away, then it may be possible to effect a repair. This is provided the corrosion of the reinforcement has not reduced the section of the reinforcing bars too much and the concrete remaining is assessed to be in a condition to receive a repair. Only a structural engineer would be able to assess whether that is the case or not. If the reinforcement has corroded too much, has lost section completely or has dropped away or the concrete has deteriorated beyond safe, economical repair then the only viable way forward is to replace with a traditional timber/felt roof.
If the reinforcement is reduced in section but is not corroded completely through and the concrete is assessed to be in good condition, then it is sometimes possible to insert a steel member (a channel or universal beam section) under the roof slab to halve the span of the slab (the slab would normally span the shortest distance) but a structural engineer would advise.
Hope this helps.
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Postby youasked » Thu Apr 02, 2009 12:43 pm

Sealing the top first would be good with liquid rubber, then allowing the structure to dry out. As Diyjack says it needs a good dose of looking at. Once repaired, the LR could be sprayed on the inside.
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Postby tcplumbing » Sat May 16, 2009 9:49 pm

Hi ...
Thanks for taking the time out to reply to my question... I think the next course of action is to chuck some money at a reputable Structural / Civil engineer to give his/her opinion on it... Maybe even take a core sample from it and assess the overall condition of the middle of the concrete & metal re-inforcement within it.
(Hopefully... the corrosion process is only affecting the outer layers where the air can get at it... Fingers crossed... the internal structure is pretty sound! X)

I think in the meantime... I'll coat the lot with liquid latex (The next spell of good weather we get!... 2013 probably!) ... and just to try and slow down the atmospheric corrosion process and allow the concrete to dry out .

This isn't a small roof mind... It's about 2.5M wide by approx 6M in length AND... it's tied into the side of our house! (eek!) and...spans over several outhouses.
In an ideal world... I'd simply pick the winning lottery numbers... have the whole lot removed and build a double decker extension! hahaha
back to reality.... wheres that phone book?

Cheers guys.
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Postby AuroraMagic » Fri Sep 17, 2010 12:23 am

By comparison I have a massive concrete roof. You can repair the reinforcing rods by simply replacing them or remove the rusted parts and seal over the ends and repatch the ceiling.
There is a chemical 'cure' for concrete cancer if the roof has that.
You need to drill to do tests to prove it before any treatment.

Sealing the top side is necessary and allow the ceiling to thoroughly dry out before considering any repair or thermal sealing takes place.
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