Shower extractor advice

[whistler]

Not sure if this should be in plumbing or building, but here goes ...

I'm renovating my bathroom and want to fit an over shower extractor fan. The ones I have been looking at show the extractor pipe exiting the roofspace via the soffit board. Heres where my problem lies. My soffits are made from asbestos. The building surveyor advised me that this is ok as long as they are not cut or drilled etc, so I'm not too keen on cutting a four inch hole in the soffit.

My questions are:-
1. Is there any safe way of cutting a hole in the asbestos (probably not?)
2. Can I feed the pipe out via the roof i.e are there any roof tiles designed to accommodate the pipe outlet?
3. My other option would be to exit via the gable wall. This would involve extending the 3 metre pipe supplied with the fan to about 6 metres. Would this be ok?
4. Apart from the electrical work, are there any other building regs I need to be aware of?

Any help/advice much appreciated

 

[^woody^]

You can cut asbestos cement board, but you just need to take precautions to not breathe the dust. Outside, with a suitable mask and a disposable overall will be OK.

There are tile vents available if you want to do that instead.

I would not extend the duct as the fan will be very inefficient with a 6m extract duct

 

[Roofer]

Depending on the type of your roof covering, to install a tile vent can range from very easy (concrete interlocking tile) to moderately difficult (slate)

It might still be preferable to cutting the soffit

 

[bathjobby]

I assume your talking of using a standard 100mm (4") ducting ? If so, most extractor fans move about 75 cubic mtrs per hour and can only push it through about 3 mtrs of ducting before becoming inefficient. I recently fitted one of these

which you can see the spec of here http://www.airflow.co.uk/products/product.asp?ProductID=11.
Using 100mm ducting these will do about 118 cubic mtrs per hour and handle 6 mtrs of ducting. they also have an iris fitted which reduces backdraft when not in use. They also come with a variety of clip in modules for different functions e.g. standard pull switch, delay timer, humidifier detector etc. They can be wall mounted which is what you see here i.e. stand about 4" proud of the wall or ceiling mounted in which case they are very slim, only about 1" proud i.e. the back cover you see fitted here comes off and the front face is fitted flush to ceiling.

Pleased with mine, the only point I would make as it isn't obvious is that the iris (shown open here) has a delayed opening, it opens about 20 secs or so after the fan is started so there is a lot of suction on the iris when it starts to open. This makes it sound like a hovercraft whilst it is opening until it is fully open, but this only takes about 10 secs.
I had a similar problem to yours and ended up taking it out through the gable end wall - normal cavity construction. At the wall I fitted to the end of the 100mm circular ducting an elbow which goes from 100mm circular to 100 x 50(ish)mm rectangle. Removed half a brick from the outside (just hand held hammer a chisel job) and this rectangular ducting fits through the slot perfectly with a bit of cement and a grill on it, job done.

 

[whistler]

Took a closer look at the asbestos sheets at weekend. Looks like the are not nailed or screwed. They appear to be slid over the top row of bricks and then into a groove in the facia board. I think it may be possible to just lift them out without any damage and then replace with plywood.

The Local Authority web site advises to double wrap in heavy duty polythene, seal and take to the LA refuse yard for free disposal.

 

[^woody^]

Don't use plyboard it will last 5 minutes. Use something like Asbestolux or Superlux which are asbestos free cement board. Then there are no long term maintenance issues

 

[Maxxy]

I'd phone ahead and double check about the free asbestos disposal service

 

[whistler]

I'd phone ahead and double check about the free asbestos disposal service

This is an extract from the local authority web site.


3. It is recommended that the panels are sprayed with water before dismantling, to minimise fibre release, for example, use garden a hose. Alternatively dismantle just after or during rain.

4. Disposable overalls, a disposable face mask (for use with asbestos) and gloves should be worn to minimise exposure during dismantling.

5. Power tools and saws should not be used, in order to minimise release of any fibres.

6. The asbestos waste should be wrapped in heavy-duty polythene sheets or bags, and sealed with tape. Overalls etc. should be disposed of in a similar manner.

7. Members of the public can dispose of asbestos waste free of charge at civic amenity sites. There is a skip at each site designated for asbestos waste alone. It is a good idea to inform the site before taking large amounts of asbestos waste.