Shaft Beside Chimney

[NORTHDUK]

I live in a mid-1930s semi-detached house. We are currently having the loft insulation renewed and new flooring put down.

Whilst preparing for the work, we discovered that a vertical brick shaft, about 12-15" square, runs down the left hand side of the chimney and seems to extend down the whole height of the house. It cannot be seen in the relevant rooms on either floor and evidently runs down inside the chimney breast. The top of the shaft is open and simply forms a hole in the corner of the loft floor. There is a strong updraught through it.

Can anyone suggest what this shaft is for and tell me whether it is safe to block the top with the new flooring?

Gordon McLaughlin

 

[NORTHDUK]

As work has progressed, we now find that there is a second shaft of the same kind running down the right hand side of the chimneys that serve the back rooms.

I have Googled for diagrams of chimney construction but none of them had these shafts and I couldn't find any text references to them. I remain stumped. Any ideas?

Gordon McLaughlin
North East UK