house centreline joist

[philrosenberg]

Hi All
I am about to board my loft - but have hit a snag and wanted some advice.

My plan was to run new 150 mm joists parallel to the current ceiling joists. The roof is a trad roof, with purlins from the 60s. The existing ceiling joists are 75 mm. The span of the new joists will be about 2.2 m. The boarding is for storage, more than just a box of Christmas decorations, but I'm not putting a bedroom up there or anything.

However when I lifted the insulation to start installation I found that there is a single 75 mm joist running at right angles laid on top of all the ceiling joists. It is nailed to each ceiling joist and runs directly down the centre of the roof. It doesn't appear to be supported other than by the ceiling joists, it actually runs down the centre of my hallway. I've attached a picture, In amongst the mess of wire and insulation you can see the ceiling joists running top to bottom and the centreline joist running side to side.

This is a bit of a pain as I would have to raise my new joists above it, reducing head room by rather a lot (it is already pretty limited). Does anyone know why this centreline joist exists? Best I can think is that it is a bit of a quick bodge instead of putting noggins in.

Unfortunately I can't run the joists in the other direction as I don't have a supporting wall to rest them on at one end.

Any thoughts or suggestions?

Phil

Untitled

• philrosenberg
• 20 Jul 2014
• 1

 

[geraldthehamster]

Search the forum for "ceiling binder".

Cheers
Richard

 

[freddiemercurystwin]

Normally you just run some 100x50's perpendicular to the existing and sit them on top.

 

[philrosenberg]

Thanks Gerald

So I googled about ceiling binders. Found this page http://www.haringey.gov.uk/note09_-_ceilings_and_flat_roofs.pdf. My ceiling binder has a clear span of 9 metres. Obviously way off scale on the chart on that page.

Could I replace it with two binders below the purlins?

The ceiling below the current binder only has span of about 1.2 m, not sure really what the binder in achieving.

Thanks again

Phil

 

[wakey77]

Hi Phil
I had a similar problem mate ceiling binders were approx 3.5m apart I just ran new 3x2 on top of the existing joists between the ceiling binders fixing them with glue and countersuit screws every 300mm the joists were also supported on 1 side by a load bearing wall then I boarded it with caberdeck.
T wasn't ideal but it's plenty sufficient for light storage.
The ceiling binders bind the rafters together stopping sagging.

 

[philrosenberg]

Cheers Freddy
That is what I thought I would have to do, but it knocks another 100 mm from the already limited head room.

Just to reiterate, the location of the binder is above our hall (bungalow), which runs nearly 8 m and is 1.2 m wide. So the span of the ceiling joists is 1.2 m, the span of the binder is nearly 8 m, with at least one join.

Can't for the life of me imagine what the binder is doing in this case apart from weighing the ceiling down a bit.

Cheers for all the advice

Phil

 

[ree]

Perhaps sister every third joist or so, and then remove the binder and see what happens?

 

[jeds]

The purpose of a binder is to load share the joists. The one you describe - over 1.2m span joists - is doing little to nothing. Your new 150mm joists will be the principle load bearers anyway so you can safely just remove the binder.

 

[philrosenberg]

Thanks for all the advice everyone
In the end I raised the new joists above the binder. Mostly because I thought that disturbing the binder would probably crack the ceiling below, even if it wasn't necessary. This also had the advantage that the new joists are now totally independent of the ceiling joists so hopefully this should mean any flex in the floor doesn't affect the ceiling.

Jeds - thanks for that - it is good to have some confirmation that my instincts were correct.