new building regulations

[Andrew Carr]

I am planning a loft conversion in the next year or two and will get plans drawn up nearer the date but I am doing some homework of my own to check if the idea if feasible/ affordable. I have looked at the building regulations and have a couple of questions

1. in the old regs there was a table of joist sizes for various spans, in the new regs this is now a trada publication (you have to buy separately) does any one know the figures have changed or would I just be paying 17-50 for tables I already have.

1. Smoke alarms have to be mains powered and linked, my house will end up 3 storeys high so can I use t&e or have to use pyro.

Thanks

Andy

[Robbo]

Might this help?

> 2. Smoke alarms have to be mains powered and linked, my house will end up > 3

How long will T & G last in an inferno?

[john]

[Dave Liquorice]

IMHO long enough for the smokes to have been triggered and everyone out. Seems rather pointless using pyro for a pure alarm in a small property. Now alarms or maintained lighting in a large place is another matter...

[Owain]

You will need triple+E (L, N, E, and link wire).

T&E will comply, as others have said you should be out of the house before the mains wiring is burnt, but if you prefer you could use one of the fire-rated plastic cables like Fire-Tuff (on TLC website), although as it's intended for fire alarm panel systems it's usually only 2-wire and screen.

Owain

[John Rumm]

Although sensible, IIUC there is no actual requirement for the alarms to have a battery backup. They should have their own circuit however.

[Owain]

AIUI alarms on their own circuit do not need back-up.

Alarms on a shared (eg lighting) crcuit do need back-up - although on some it's provided by a whopping big capacitor.

My preference is for a shared circuit with back-up, because if the lights go out it's more obvious the MCB's tripped.

Owain

[Robbo]

Very true, and there are probably more legal implications to those areas as well.

Given the choice, and a few extra seconds for escape I would plum for the Pyro.

[Stephen Dawson]

I reckon you will change your mind once you see he cost of the materials and the cost of the labour time to install it.

[legin]

The local building inspector asks for battery back up mains interlinked detectors in the Mids. He might be wrong but given that they only cost marginally more and you will probably only need three, I would recommend that these are used. Perhaps he is just covering his back as he would not no if they are on a ddicated circuit. With regards to the joist spans I would ring building control and ask them what they would be happy with for a given span, centres of joists. I have found certain inspectors to be very helpful. The old tables were a very good guide so you could always look up the recommendations on those. That way you could ask if 8 by 2 was still alright for a 3.9m span and at least the inspector will know that you have made some effort. Regards Legin

[Lobster]

Both correct; as stated in 2000 building regs (Part B). Can't see any point in not always having the battery backup TBH.

Yes - it does seem odd to me that on a dedicated alarm circuit you

*don't* need backup, exactly for the above reason. With a numpty householder the MCB could be permanently switched off and/or tripped and numpty would never be any the wiser.

David

[Tony Bryer]

Or check out the first option on

FP200 Gold®

A unique fire resistant cable incorporating hard skin Insudite? insulation. The right choice for fire alarms and emergency lighting with minimum installed costs. The original, easy to install alternative to MICC with unmatched combination of rigidity and ease of bending.

I only know about this through seeing the offcuts in next door's skip a few months back.

[cucumber]

My alarms chrip every so often if the mains power is switched off and they're running on backup battery only. Useful feature which probably should be a requirement.