Ceiling under Concrete Flat Roof Information, help and advice on maintaining, installing and repairing a flat roof. Post your questions and view answers here

[Dinger]

Due to what would appear to have been a "Cold Roof Contruction", we had our kitchen ceiling collapse on us over the last week-end. We have now cleared the total scene and are left with the ceramic under brickwork showing and the batons that held the previous ceiling, under a concrete flat roof.

Now it has been suggested that instead of the previous Cold Roof Construction we now go for a warm roof construction, but initially this looks like an expensive situation that we can ill afford.

The flat roof itself is used as a "Patio" and "Summer Dining Area" so there is quite a bit of traffic moving across it.

The surface is starting to peel and we were, prior to the collapse of the ceiling underneath, going to re-seal the roof with Thompsons Roof Seal after cleaning off the dirt & grime etc.

One train of thought that has already been suggested to us was:

To strip the roof completely and not seal it and remove any other covering, which there isn't, and then put on felt. Once that was done with a hot torch then put on a rigid plastic insulation and finally topping this with paving slabs.

This unfortunately would be expensive.

Our train of thought was:

Clean & seal the flat roof with Thompsons Roof Seal.

Either take off & replace or remove completely the existing ceiling support cross members and put in new insulated backed plaster board with adhesive cement.

The only problem I could see with "Our Train of Thought" was the lack of ventilation which would then give any build up of condensation nowhere to go & then the same thing would happen over the cvourse of time as has happend now and the ceiling would collapse again.

Any suggestions & guidance would be sincerely appreciated.

[stoneyboy]

Dinger,
Unusual time of year for a ceiling to collapse - are you sure that the problem is not related to water penetration from above.
If you have the headroom form a ventilated cavity directly below the concrete and an insulated ceiling below that. Re-coat the roof as you suggest but you should still lay a covering to protect the sealed surface.
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[Dinger]

Hi Stoneyboy,

Thank you for your response.

You would not have been aware, as my Country of Residence is not given in my profile, but I am in the Center of France and in a region where there was very heavy snow in January February & then again heavy rain thereafter.

The exterior Roof Seal has cracked in places and whilst it is not excessive, water has obviously seeped in and furthermore when the cottage was closed up during the middle of Jan/Feb when we were away on holiday abroad,and the interior not being central heated as this is only done by means of a woodburner when we are in residence,you can imagine the possible condensation that arose and which did not ventilate.

Prior to our purchase some 4 years ago, the house was shut up asnd vacant for possibly 2-3 years or more, so it has had plenty of time to deteriorate in between the underside of the concrete/ceramic brickwork and the polystyrene backed plasterboard. It collapsed possibly as a result of deterioration over time.

Are you suggesting that after applying the "Thomsons Roof Sealant" and then allowing for a drying period, that we put down soemthing like Bitumastic Felt or Rubberoid as it used to be called when I was a youngster and perhaps seal the edges with a blowlamp to seal it even further?

Once again thank you for taking the time to respond and I look forward to your further advice

[stoneyboy]

Dinger,
You may be successful in sealing the roof with Thomsons seal but you may have to use a seal incorporating glass fibres on the weaker areas. Once this is done you should cover the area with lightweight synthetic tiles to protect the surface.
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