Loft joists strong enough?

[Roger465]

Hi all – I've just moved into a new house built by Redrow, and there’s a decent pitch to the roof, so I want to board the loft for storage purposes. However, the joists seem to be on the thin side – no doubt to save money in construction.

Of course, it was a few weeks ago, and I didn’t make a note of just HOW thin they were, but of course all you experts out there will know what’s used nowadays anyway

Will modern joists take boarding? I’m not making a loft conversion – just some storage space. However, I do weigh 17 stone... I suppose, if the boards are screwed to the joists, the combination of boards and joists should create a fairly rigid structure... what do you think?

Thanks guys

 

[GoingDigital]

The joists are usually only strong enough hold the wight of the plasterboard ceiling. Although there is no real risk of them breaking they will generally bow under the weight over the years causing your ceiling to deform.

Seeing as how there is usually insufficient depth to put adequate insulation under boards the general advice is to lay some new joists across the existing ones to spread the wight across multiple joists and give you the depth to put adequate insulation under your boards.

 

[Roger465]

Seeing as how there is usually insufficient depth to put adequate insulation under boards the general advice is to lay some new joists across the existing ones to spread the wight across multiple joists and give you the depth to put adequate insulation under your boards.

Bu**er - thanks for the advice. I told a look in the attic when I moved in, and I THINK there's 6" of insulation there - must check again.

If I did lay heavier joists, what would I hang them from? Would I have to attach those sort of metal joist-hanger thingies to the gable walls, or would I somehow attach the new joists to the rafters?

Thanks again...

 

[oellph]

I think I'm going to have to do the same. We have an old 1890's house with two loft spaces. Aside from the loft hatch being super small and requiring enlargement, the joists are also only 2" wide.

 

[JohnD]

If either of you want anything other than a guess, you are going to have to tell us the width, depth and spacing of the timbers, and their length between supporting walls, and attach pictures showing how the roof is constructed.

 

[Roger465]

If either of you want anything other than a guess, you are going to have to tell us the width, depth and spacing of the timbers, and their length between supporting walls, and attach pictures showing how the roof is constructed.

Thanks - will do.

 

[noseall]

I think I'm going to have to do the same. We have an old 1890's house with two loft spaces. Aside from the loft hatch being super small and requiring enlargement, the joists are also only 2" wide.

2" wide is a good width for most joists.

 

[Roger465]

OK guys, sory for the delay - chest infection.

Think this is going to be a non-starter:

(1) There's about a foot deep of insulation, including several inches just laid on top of the joists, so you've got to poke around in it to try and feel where they are

(2) The joists are 4" x 1+1/2" - and they seem to be about 2 foot apart.

Pics:

www.rogerfenton.com/attic/DSCN1794.JPG
www.rogerfenton.com/attic/DSCN1795.JPG
www.rogerfenton.com/attic/DSCN1796.JPG
www.rogerfenton.com/attic/DSCN1797.JPG

 

[JohnD]

Roger465, you have a modern Trussed Rafter roof and the trusses are not supposed to be strong enough for walking on. I would go for cross-battens screwed to them at right-angles, with flooring ply screwed to the battens. When screwed together the deck is surprisingly rigid and will spread your weight over several trusses while you clamber about.

However this method does not add to the overall strength of the ceiling so you can't put a piano up there or hold parties.

the deeper the battens are, the better, this improves their rigidity and also allows you to run the thick insulation between them.

 

[Roger465]

Roger465, you have a modern Trussed Rafter roof and the trusses are not supposed to be strong enough for walking on. I would go for cross-battens screwed to them at right-angles, with flooring ply screwed to the battens. When screwed together the deck is surprisingly rigid and will spread your weight over several trusses while you clamber about.

However this method does not add to the overall strength of the ceiling so you can't put a piano up there or hold parties.

the deeper the battens are, the better, this improves their rigidity and also allows you to run the thick insulation between them.

Heh - no, I'm crap on the piano. Just want a bit of storage really...

Thanks a lot for your help - it's much appreciated.

Roger

 

[narcogarola]

hello all...

sorry to hijack post but there seems to be quite a few posts already regarding loft flooring etc... but came across roger's pictures and i think his loft is very similar to mine...

same sort of situation really... living in a standard modern built house, wanting to floor the loft for some extra storage space...

bopping up there, there seems to be 2 layers of insulation, the top layer covering the joists etc... originally i thought, just buy the boards and screw them in no hassle... but now on more research with regards to wires and pipes etc "cross battening" seems to be the general advice given to people doing this kind of job...

the joists (are they joists or battens?) going across the loft are 3cm wide x 9cm high and theres 2 rows of 2cm x 9cm laid flat on top of the original joists going diagonally across corner to corner of the central bit of the loft... please excuse my technical jargon... i am a DIY novice...!!!

with these pieces of diagonal wood, is this a starter for the height of my "cross battening"? is it wise to squeeze the 2 layers of insulation into the 11cm gap?

or should i increase the height further? what would you's suggest?

as i said i'm a bit of a noob in DIY... so any help would be very grateful...

here's some pictures for extra info...

also, please excuse the panoramics, but thought i'd use it so you can see more of the loft...

this area i have lifted up a lot of covering insulation as you can see in the background. i have laid some boards down, purely so i can walk around easily. nothing is fixed down yet. that pipe is an extractor vent from the bathroom... should i just work round it? or lift it up so the final boards will be underneath the pipe? ... so "cross battening"... where i have laid the boards, that is the direction i should cross batten? and eventually i should lay the boards back the other direction?

you can see the diagonal pieces of wood going corner to corner going underneath more insulation.

i appreciate as much help as possible... i just don't want to do it wrong and do a bodge job of it all

thanks for all the help.

 

[JohnD]

is it wise to squeeze the 2 layers of insulation into the 11cm gap?

That will give you just 110mm of insulation which is not much.

Insulation depends on thickness

250mm of insulation is a lot, and the current standard. If you take 250mm thickness and squash it to just 110 mm you only have 110mm of insulation.

Squashing it down onto the ceilings will probably also bend the plasterboard, or cause cracks in the ceilings

 

[narcogarola]

hi, thanks john d,

so counter battens 30 x 60mm? 60 height i take it...

and screws... what kind of screws? should i drill a hole first? or screw directly through?

and length, i suppose whatever length i choose?

thanks again...

 

[narcogarola]

sorry my previous post should have said

"so counter battens 30 x 160mm? 160 height i take it... "

..............

hello all... after more research and boppin to my local wickes i'm still non the wiser

ok...

i live in a modern 2 bed house built 5 years ago. planning to board loft for extra storage. records, bits and bobs etc.

joists are 90mm high x 33mm wide.
gaps in between joists are average 57cm
2 diagonal bits of wood are 20mm high x 90mm wide

little diagram to show layout

i already have 1 layer of insulation in between joists, + another layer of insulation laid over the joists and the diagonal pieces of wood.

my dilemma: what size battens to use?

ok... to increase the height of insulation to 270mm, i will have to cross batten with 160mm high bits of wood.

isn't this going to be too heavy with the boards as well? i went into wickes today and asked someone there. he said it was going to be too heavy.

do i have to increase the height to 270mm? or can i get away with something in between?

any help is well appreciated...

thanks in advance...