I understand what you are saying but my engineer has specified the fire stopping that is illustrated in TGD B for my party wall but yet I have been told that this detail has never performed in a fire and does not give me one hour as the wall does. Once the roof collapses this detail fails and fire spreads into my house or my neighbours but yet this is what we are told to use in TGD B but on the other hand im been told not to use what is illustrated in TGD B. I dont know what to do!!!!
Does the detail in TGD B work or not. Is there a certificate I can get from the manufacturer that tells me it has been tested and is approved in this location on top of a party wall?
This is very specialist so read the disclaimer in my sig and take it to heart, but I'm not leaving this hanging after your warning on another thread.
First, for your peace of mind.
Get on the phone and talk this out with your local fire officer.
They are public sector empoyees and have a duty to assist members of the public.
They don't want to be called out to avoidable fires, so they have an added motivation.
They will give you chapter and verse on the details.
As to the logic you use above - think about it for a minute.
Fire and flames are trying to get into the adjoining house from a build up of hot air and flames in your house under an impervious tile or slate roof.
The tile or slate roof is not fire rated or required to be so under the regulations - why?
Becase, and your fire office inquiry will confirm this, once the roof collapses or the covering is seriously breached, the heat can escape out, lowering the internal temperature and making it less likely the fire will spread laterally.
We used the TGD detail on a penthouse in town once and one of them went on fire.
Roof burnt through, the adjoining penthouses were okay.
All this is literally up in the air if there is a strong directional wind fanning the flames.
Just remember, the detail at the top of the party wall needs the battens broken - its the charring of the battens that spreads the fire even if the rest of the detail is in.
Also the fire stopping must fill the triangle under the felt and must fill in between one line of battens and the next as well as separating the ends from each other to prevent charring.
You will hear different arguments about different materials, with some favouring the more robust mortar fill and others favouring the potentially less robust but usefully flexible Rockwool. A judicious use of both with some fire sealent may give the best result, but its really down to a matter of detail workmanship on site and if there is a company offering to certify the work you'll be following their approved details.
If you're really panicking, why not go for a planning permission and raise the party walls 375mm vertically over the roof finish - that's both a thernal break and a shield against blow over to a small degree.
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Second, for your safety.
Laypersons or persons who don't understand the principles involved and the pitfalls should not attempt fire proofing without professional guidance.
There are firms claiming expertise out there who may seal a particular thing, but might miss something in the over view I posted above, which is not exhaustive.
My best advice is to employ an expert to offer advice and a competent, skilled person with experience of fire sealing to carry out the work - and also issue a certificate.
ONQ.
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All advice on AAM is remote from the situation and cannot be relied upon as a defence or support - in and of itself - should legal action be taken.
Competent legal and building professionals should be asked to advise in Real Life with rights to inspect and issue reports on the matters at hand.