running a soil stack through a 60 minute fire ceiling

My local Building Inspector asked that I upgrade to 60 minutes fire resistance between a pair of maisonettes, as the back yard is too small to be a 'place of safety' for the rear-facing bedrooms. (I would be incorporating an extra bedroom at the back of each maisonette.)

I want to move the soil stack inside but it would penetrate a 60 minute rated fire retarding ceiling. I would be enclosing all the waste plumbing in a service enclosure but the soil, water and gas would have to run between floors. I am hoping to conceal the toilet cistern and shower controls in the same service enclosure. Basically, there will be numerous penetrations into this enclosure.

How will it be possible to maintain 60 minutes of fire resistance between the maisonettes?

There are products on the market that can seal various penetrations but one would assume it'd be cheaper and less hassle if you were to keep the soil pipe in its current location and fire protect that rather than moving it internally and then going through the process of fire-stopping each penetration?

DevilDamo said:

There are products on the market that can seal various penetrations but one would assume it'd be cheaper and less hassle if you were to keep the soil pipe in its current location and fire protect that rather than moving it internally and then going through the process of fire-stopping each penetration?

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The new bedrooms replace the old bathroom, scullery and outside toilet. The new bathrooms are internal and about 4m from the old (rusted through) soil stack. I could put a new external soil stack just over 1m from the new toilets but would have to run all the drains, including the toilet drain, through 6" joists (adjacent to a new 900 mm supporting beam).

Is there such a thing as a (steel or reinforce concrete) channel that could take the 1st floor drains and support floor joists on each side? One end would be fully supported in the outside wall. The other end might need to rest on a corbel off the supporting wall or even a second 1.7m beam at right angles.

DevilDamo said:

There are products on the market that can seal various penetrations

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Can FloPlast Fire Collars provide protection for the soil pipe going through a ceiling?

I'm not 100% sure. You'd be better off speaking to their technical department. When you say ceiling, is there a void or is the ceiling the line of compartmentation?

There's hundreds of collars on the market for all situations. Google and you'll be overwhelmed. Just make sure the one you specify is 60min rated.

If it's of interest, the way they work is; when they are exposed to a certain operating temperture they expand and close off the hole formed by the pipe. The temperature is about a billion degrees so in practice it will go off at roughly the same time the whole building turns to charcoal and hits the deck. But at least you know you will be safe.

Face any enclosures or boxing's-in with 1 hour fire rated plasterboard.

DevilDamo said:

I'm not 100% sure. You'd be better off speaking to their technical department. When you say ceiling, is there a void or is the ceiling the line of compartmentation?

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The fire barrier between the 2 floors is the plasterboard ceiling (and stairwell).

In addition to that ceiling on the first floor joists, I'll also have suspended ceilings over the smaller rooms (just not the lounge) to improve proportions, reduce noise, hide ducts and take recessed lights (including the bathrooms). The suspended ceiling in the downstairs bathroom could also hide a big fire collar around the soil downpipe.

With a fire collar on the soil downpipe, the service enclosures become cosmetic (only up to the false ceiling) and I won't have to seal all the penetrations through them.

I'd probably complete the compartmentation with intumescent sleeves around the electric main. the lounge ceiling light and various switches and sockets on the stairwell partition. Finally, I'd seal around the gas and water mains.

Rest assured, I'm only trying to second guess the Building Engineer and the local Building Inspector to get an initial layout for remodelling that could work.