Blocking off inside a Chimney - ideas

Discussion in 'UK DIY' started by bp, Jul 5, 2007.

  1. bp

    bp Guest


    I want some advice on blocking up the inside of a fireplace.

    I live in an old terraced house which has a chimney and fireplace.

    I have recently had the chimney wall and fireplace all re-plastered.
    I dont have a fire and I dont want one. The fireplace is currenlty
    open and it has been plastered inside. I have had it swept.

    I just want to keep it like that as a decorative feature. But I need
    to block off the inside to prevent soot from falling down into the
    fireplace floor. I know I have to keep a ventilation hole

    The arch of the fireplace is visible, as is a arch steel lintel. how
    can I block off the inside. I have had many thoughts but cant see how
    any of them would work.

    The plasterer said I could fix a piece of hardboard on the inside,
    curved to match the arch, but I cant see a way of fixing this to the
    inside. ALso this wont cover the steel lintel. This is currently
    very rusty, I dont mind keeping this visible but and I cant see how I
    could tidy this up. My preference would be to hide it.

    The plasterer did not plaster the edge where the lintel is so
    brickwork is visible there.

    I tried messing about with some board but cant get it to look right.
    Fixing it to the wall is difficult on on side as on the inside the
    brickwork forms steps.

    Has anyone done/seen anything like this before. I just some some
    ideas or an approach really. I am assuming pasterboard is out of the
    question as it cant be curved. Arch forming kits are a bit of
    overkill for this, and I probably could not plaster the arch anyway.

    Many Thanks

    bp, Jul 5, 2007
    1. Advertisements

  2. bp

    Thomarse Guest

    Best thing to do would be to keep the fireplace! - helps keep air
    circulation the your house and prevent damp, is a nice feature AND
    will add value to your home.. I really cant stand fireplaces being
    blocked up, it seems a waste and makes teh house loose charachter.

    That said, I've just done the opposite to you and Ive knocked out
    fireplaces in my old victorian terrace and restored them... But in the
    main bedroom, we didnt really want the fireplace but wanted the
    "feature". So I knocked it out and had a similar problem to you. I put
    a few strips of batten around the inside, quite high up, higher than
    the highest part of the arch and then attached plywood to that, I also
    added some downlights to this to create a nice feature effect, it
    looks nice on teh old brickwork, which I've painted up.

    The ply isnt curved, just plain a flat, but is high enough that you
    dont see it. As for the rusty arched lintel, I am going to wire brush
    that down, treat it and then paint it with an appropriate paint -
    making that part of the feature. Obviously when I knocked out the
    bricked up fireplace I was left with rough plaster edges, so I put
    beading up the sides, and made mitred beading around teh arch at teh
    top and plastered up to that.

    I suppose you coudl do a similar thing with hardboard and curve it,
    but I didnt see the point in teh extra effort when you dont se up
    there if you put it high enough anyway

    Thomarse, Jul 5, 2007
    1. Advertisements

  3. bp


    Chimney balloons are available for sealing up chmineys - they leave a
    gap for some ventilation and can be removed if necessary.

    Never used them tho'

    , Jul 5, 2007
  4. bp

    bp Guest


    It looks like I have not explained my self propery. I have done the
    same thing as you. The original fireplaces were bricked up. I opened
    them. I didn't want a fire and just want it open as a feature. But
    the inside of the fire place is open (all the way to the pot at the
    top). I have had it swept but I want to block it off inside just as
    you have done. Your suggestion of battons and plywood seems the best
    way forward.

    A few questions then

    Should I treat the ply and any way (i.e as for extrnal use). Guess
    the same appplie to the battens. DId you go round teh edge with some
    sealer to fill in the small holes - otherwise I'd guess you would
    still get small bits of dirt etc coming down

    How did you fix the battens to the inside of the wall. I had a quick
    look up and there not much room to drill holes - did you glue.

    Can you explain the mitred beading round the arch as I have no idea
    what this is. I have seen beading that is used by plasterers, but
    could not see how it could be used to create the arch - it does not
    seem to be bendable. The plasterer has plastered the arch but not
    that well as he assumned I would tidy up the arch. I could wire brush
    the steel and paint that - thats a great tip thanks. That leaves the
    exposed arch edge.

    Thanks for the help

    bp, Jul 5, 2007
  5. I've done exactly this. If it backs onto an outside wall, I would
    suggest you ventilate the flue to the outside rather than the
    inside. Otherwise you'll lose up to a kW of heat up the chimney
    in winter.

    I put an air brick from the flue to outside a few courses of bricks
    above the top of the fireplace. I then blocked off the flue using
    a piece of plasterboard in the top of the fireplace glued in place
    with bonding coar plaster. When fitting it, I put a layer of loft
    insulation on top of the plasterboard, partly to prevent it getting
    cold and forming condensation, but mainly to cushion any debris
    falling down the flue to reduce chance of it damaging the plaster-
    board. The back wall of the fireplace was only a single skin brick
    wall, and to prevent that getting cold and forming condensation and
    mold, I lined it with 25mm cellotex and then plasterboard, and
    plastered the whole inside.

    I dug out the floor of the fireplace down to the slate damp course
    in the brickwork, fitted a damp proof membrane, layed about 6" of
    cement and vermaculite insulation and brought it up to floor level
    with mortar. This should enable it to be used for a fire in the
    future (if the flue is reestabled and the cellotex removed).
    Fireplaces often relied on regular fires to keep damp out of the
    base and hearth, and without fires, mine was slightly damp as the
    infill wicked moisture up from the earth.

    I dropped a lighting cable down the flue from the loft, to enable
    a concealed light to be fitted in the fireplace.
    Andrew Gabriel, Jul 5, 2007
  6. bp

    Thomarse Guest


    I see, it does sound very similar to what I have done upstairs. On the
    side of the plywood that face up into teh chimney I have treated that
    with sonme external wood preserver, the bit that is visible, i've just
    used standard satin paint, or whatever you want.

    As for any small gaps that were left around the edges, I have used
    decorators chaulk to seal those.

    I forgot to say in my original reply that I put a vent in the plywood
    too, just s standard plastic one, and the lighst either side.

    I must admit, getig the batten in place was the hardest part and I did
    curse quite alot while doing it...I had to drill at a slight angle as
    my drill was too bit for teh chimney hole, but I wasnt worried too
    much about teh neatness of the batten, as long as they were secrured
    well, they are now hidden by the plywood. I didnt find a way to attach
    the ply to the front arched edge as there was no way I could drill up
    there, but the ply seems to hold well enough along the 3 edges.

    When I said Mitred beading, I used standard wooden beading, the right
    depth for the plaster and attached a stip up each side of the opening,
    in the room. To create teh arch effect at teh top I cut teh battem
    into 5 mitred lenths, which when attached creasted the arch i required
    all the way around. This was also trickey as the old plaster was very
    deep and varyied greatly in depth around the opening.
    Thomarse, Jul 6, 2007
    Londoncityslicker, Jul 6, 2007
    1. Advertisements

Ask a Question

Want to reply to this thread or ask your own question?

You'll need to choose a username for the site, which only take a couple of moments (here). After that, you can post your question and our members will help you out.