Trussed Roof - Chimney Removal Question

[machineage]

Hi all!

I am wanting to take down a chimney in my bungalow. The roof is constructed from trusses which are at 600mm centres. Just before the chimney there is an additional truss which is 320mm from the previous truss. The next truss on the other side of the chimney is 740mm apart. In between these trusses is a rafter which is attached to a support timber which is nailed to the neighbouring trusses. I've enclosed a plan diagram here along with a few photos which should explain the details better.

What needs to be done here to ensure the integrity of the roof if the chimney is to be removed?

Thanks!

 

[Doggit]

First make sure that the support timbers are firmly attached to the side trusses, then provide extra supports from the centre support either side of the chimney, to the roof joist just above them; this'll provide interim support whilst the chimneys coming out. Then remove the chimney and install the missing trusses to the apex, and then insert the central supports. from the ceiling joists to the apex.

Alternatively, you could support the short roof joists, and then sister a new joist alongside it; I'm not sure where the loft hatch is, and you're a bit short of space, but it could be insterted from outside the roof, and then dropped back down into position.

 

[machineage]

Thanks Doggit

I think this is a situation where a picture paints a thousand words 'cause I'm not sure I followed you there

The horizontal timber that spans the two trusses is firmly held by two nails into each truss. The chimney is un-conncted to these timbers - they look to have been just placed up against the chimney prior to being nailed to the trusses. You suggest to 'provide extra supports from the centre support either side of the chimney, to the roof joist just above them' Could you elaborate on that?

The chimney coming down won't affect the roof as it stands - there are no timbers or trusses attached to the chimney - it would just leave a big hole where it once sat.

Indeed space is very limited - and there's no way I can get decent sized timbers to this location through the presently restricted access hatch.

 

[Nige F]

Next to the chimney - is that a gas fire/boiler flue ? is that staying or going ? Unusual to have a chimney built of lightweight blocks, what's outside ?

 

[machineage]

Yes it's a boiler flue and it's going / defunct. The chimney is brick outside - if you look on the fourth photo where the truss web meets the top chord you will see the transition from block to brick. The property was built circa 1980.