Meaning that they should be at 400mm in the old days they were always 16" centres , I don't think there is enough support with just one joist in the middle!! All the boarding I have done (even metal frame work) has always been 400mm centres and always will be in my book.
I've just had my builder check the joists and he says:
"There's no rot ... only issue with them is they are too thin, joists are only 70mm deep (instead of 170mm). The joists themselves are bowed and weak, moving under pressure when applied from above in the loft".
The reason we didn't originally opt for joist strengthening or new joists completely was the fact we are doing a loft conversion in a couple of years so didn't want to invest heavily in new joists that (we were told) wouldn't be needed once the loft extension floor joists are suspended above them on a much more rigid structure.
The new ceiling work in that second bedroom was for cometic purposes only.
Okay… so I chatted further with my builder this morning. He is actually recommending we tackle this issue properly and don’t simply opt for a quick skim over or the dropped ceiling route (which I had him start without realising the excessive loss of height).
The issues we have are the current loft joists are only 70mm thick, they are bowed and weak bending easily under foot … as a result our loft is not really safe for walking on or storage and one of the ceilings (second bedroom) is sagging badly.
Another factor for consideration is we would like a dorma loft extension adding a couple of years down the line, so any work that is or isn’t carried out now will have certain implications.
His recommended route is now the following:
Cross batten the existing joists with timber battens approx 150–170mm thick, these battens will be fixed to the top of our current joists across the whole loft space. A 250x50 timber cross beam frame (as far as I understood) will be screwed into the party walls for the cross battens to sit on, as opposed to the battens actually going into the party wall brick work (which will require party wall agreements).
The battens will then be boarded to create a new loft floor… which he is suggesting will be of good enough quality to serve as our dorma loft conversion floor in the future, would this be correct?? So in effect we’re laying the dorma loft conversion flooring now.
Can I be sure that any future loft conversion company will be satisfied with this floor he creates and will it be fit for purpose?
The original bowed joists will then be screwed up and into the cross battens, relieving as much of the bowing as possible (but not all).
Our second bedroom ceiling is currently plyboard with plaster (not lath and plaster) … he will remove the old plaster but use the plyboard and replaster onto it and the now secure joists, skim and finish.
Here's the quote and work summary in full, does this sound right?
Supply and fit a new cross timber joists over the existing joists.
Main timber = 50 X 250mm: Used all the way along the party wall and all around of the chimney breast. This main timber will allow us to fit a new cross joist over the complete loft floor with 400mm gap in between each joist.
Cross joist = 50 X 170mm: and use 50mm Jiffy joist hanger to fix the timber joist together.
Supply and fit a 200mm thick Rockwool loft insulations on the whole place in the loft
Supply and fit a new 18mm chip boards to allow use of loft space as storage and also allow floor to be used as the future loft extension floor.
We have had our say and you keep coming back and asking if this is right or that is right and we have told you what we thought, so why don't you do what people normally do and get 3 quotes off reputable and recommended builders, If this boy has done work for you before and your happy with him then let him do the job..