Loft boarding-counter battening advice.

[mal79]

Hi all,

My house is a 1900's terraced house and I am looking to counter batten across the joists in my loft and board it to provide a level surface for light storage. I have a couple of questions that I would like to clarify before I start buying materials. The existing joists are 3 3/8" deep x 2" wide, spaced about 14-15" centres and resting on a supporting wall in the centre of the house.

Firstly, in the centre of the the loft here is a support in between the two struts, similar to this diagram: http://diydata.com/general_building/roof_construction/cut_roof2.gif. This is actually resting on top of a joist and thus precluding a single batten across all joists. I would like to secure the battens to this joist, so what is the best way to do so? Could I use some kind of bracket?

Secondly, the maximum span of battens will be 3.9m. I'm not sure how successful I will be in manoeuvring a batten on this length into and around the loft. Is it ok to have two battens joining at close proximity on same joist?

Finally, fixing batten to moist. Do I screwed at angle though batten into joist or use L shaped brackets?

Thanks, Mal

 

[regsmyth]

I suspect your joists are not up to taking any additional support. I bet they already sag.
What you might do is fit a few good sized joists in between your existing ones, packed up to not touch the ceiling. You could then counter batten these, though your battens would be quite hefty depending on the span between your new introduced joists.
You will lose a few inches of height.
Hope this is clear.

 

[mal79]

Thank you for the reply Reg.

There doesn't appear to be any sagging of the joists, though I have been meaning to get a laser level for ages...

The construction of my roof appears to have the joists directly on the external wall without a wall plate, then a cross timber above the joists supporting the rafters. So presumably, I am limited to the same height of joist at wall end? This and the prospect of dealing with joists the length of the loft puts the job beyond what I am capable of. One day I would love a proper loft conversion, but not anytime soon...

So regards to boarding the loft for storage, to avoid introducing additional weight, would I be better off just laying T&G boards direct to joists?

The loft had been partially boarded previously but with whatever materials were available to the previous owner (ply, mdf, planks, cupboard doors). We had a fair bit of storage up there, but concentrated in a small space - I want to spread the load around. On that note, where can I find information on the loads that the existing joists can take?

 

[regsmyth]

Well you can get definitive information about joist sizes and loadings from the building regs, but it's quite a lot to wade through.
If they don't sag that's good.
Is the ceiling lath or plasterboard?

I can't quite picture your situation - do the joists run parallel to the rafters? Do the joist bear on an internal masonry wall?

Either way, probably the best thing is to go up there and bounce around on the joists for a bit (probably best to spread your load over at least a couple of joists with some boarding) and get someone below to see if the ceiling likes it. If it seems ok, you're probably fine to just board over the existing joists.

You can get a build up of moisture on the underside of the boards if your house is damp and the ceiling old - the humidity will go through the ceiling unless it has a vapour barrier.

 

[mal79]

Have had a look at a few online span tables but they are from a new build point of view - the minimum joist height is an extra 10mm than what I have and is structural timber. So I know that the load my joists can take is less, but not how much less...

The main part of house is about 6 metres front to back with a supporting wall about in the middle. Upstairs this wall separates the master bedroom and landing/second bedroom. The master bedroom ceiling is lath, the rest plasterboard. The joists are supported on this wall in the centre. About midway between the central wall and the external wall there is a joist binder...

Then at the external wall end, the joists rest directly on the masonry and another timber just like the binder on top of that. This is where the rafters birdmouth cut fits. If that wasn't there new taller joists would fit with tapered ends limited only by the pitch of the roof. Because of this, any new joists would be limited to existing height until off the wall, even less if they have to be raised to clear the ceiling! I wouldn't like to attempt to calculate the load on a joist shaped like that...

 

[mal79]

Such is the pace of my DIY endeavors, the loft is still not boarded...

I have kind of abandoned the idea of counter battening, opting instead to board (T&G chipboard) directly to ceiling joists to minimise the extra weight. The the issue remains of the uneveness in the loft, but the majority of this can be mitigated by cutting the boards to fit. However I still have the issue of the horizontal beam between the purlin struts which is resting on a joist, effectively giving me a double height joist in the centre of the loft:

I would like to board up to this centre joist to avoid having to step across a two joist gap in the loft when I go up there. To do this I need to make this joist wider so that the boards end on a solid surface rather than thin air. As per the above diagram (lets hope it worked this time), the area of concern is that between where the purlin struts meet the support above the joist.

Can I attach a batten or angle iron to both sides of the joist within this area? I did think that noggins might work, but seeing as I would need them in the same area either side of the joist to support the board edges, I worried about putting too many screws through a localised area of joist.

Thanks for your advice.

Mal