Building chimney off of 1st floor slab

clint_eastman

Hi, Just looking for ideas or opinions on this.

I will be installing a double sided "tunnel" multi fuel stove in my new build. I haven't built any chimney surround yet on the ground floor but have been told by slab manufacturers that I can build my chimney off of the 1st floor slab direct. My issue is that I want to start my roof next week but can't build my chimney off the 1st floor as the clay liners have nothing to prop them i.e. I left a rectangular hole in the slab as I didn't know what I was planning at the time the slab went in. As far as I can see I have a couple of options:

1. Build a false chimney on the roof and plough on with the roofing. This will allow me to use a twin walled SS flue from the 1st floor up to the false chimney when my stove is installed. The flue could then be boxed off.

2. Build a masonary chimney now off of the slab with clay flue liners. When my stove is installed its flue will sit up into the clay liners which start from the 1st floor. I'll then build the chimney surround.

Option 2 is preferred (cheaper) but how do I support the liners. Could I cast some sort of support with a hole for the liners? Or is there a proprietary solid block that you can get with a hole in them that could be laid across the chimney at say every course interval?

I've attached some photos showing where the stove and chimney will go on the ground floor with the ext air supply, the next photo just shows the hole left in the slab for the flue to pass through.

Appreciate any input.

FesterBeatty

...surely there's a structural engineer on board such a project who can advise?

RKQ

+1
You need to discuss this with a Structural Engineer with full PI insurance.

Can you post a photo of the stove?
I assume you will build some sort of chimney breast on the ground floor?

There are a number of companies that supply pre-cast concrete or plumice chimneys. Maybe one of these could be used. Maybe they can help you. I'll PM a company name.

Interesting query, best of luck.

clint_eastman

Thanks guys. Yeah, a structural engineer will be involved but I'm still looking for other opinions/ideas. Once the stove goes in, the chimney brest will be built around it. The first floor chimney load will be carried by the slab and this has been passed by the slab supplier. Thanks for the input.

scanner1

Hi Clint,

I did this myself a few months back, the only difference was it was between the kitchen/dining and the sun-room so there was some external walls to build around and take half the load, even with this my engineer stated we use quinlite blocks after installing the flu gatherer on the 1st floor (until the last 3 rows back to normal blocks) we just slabbed the blocks then to allow them to be skimmed easier.

gillad

a flue gatherer will support the flues

martin46585

check out schiedels prefabricated chimney flues, light weight and also with an air intake if needed.[EMAIL="www.schiedel.ie"]www.schiedel.ie[/EMAIL]

FesterBeatty

Just out of curiosity - you note that there 'will be' an engineer or board, yet it appears from your photos that construction has already commenced. If the engineer is not yet involved then who specified the precast slabs, designed the loadbearing masonry walls, lintels, foundations, inspected ground conditions etc? If an engineer only comes on board later in the day how will he provide a cert of compliance?

clint_eastman

FesterBeatty wrote: »

Just out of curiosity - you note that there 'will be' an engineer or board, yet it appears from your photos that construction has already commenced. If the engineer is not yet involved then who specified the precast slabs, designed the loadbearing masonry walls, lintels, foundations, inspected ground conditions etc? If an engineer only comes on board later in the day how will he provide a cert of compliance?

Engineer is on board, relax its a general question to get ideas and experiences from people who have done similar installations. I've gotten some great answers and PMs, this is really all I wanted. Thanks.