Flooring a trussed attic - is this ok?

gyppo

Hi All,

I have a 25 year old bungalow with a trussed roof. Trusses are spaced 500mm apart. The previous owner had 8x4 sheets of 1/2" chipboard flooring the central section of the roof.

However, I want to remove the existing crappy sheets and replace with 3/4 2x8 osb t&g sheeting. The purpose of the floor will be only for light storage. I've never felt too confident on the existing chipboard stuff.

My questions are:

1 - will the 3/4 osb sheeting add additional weight/load on the roof trusses?
(note that below the central section of the roof trusses is a 4' wide hallway - I would presume the bottom section of the trusses are resting on this wall??)

2 - previous genius nailed the chipboard sheets instead of screwing them - though probably before the ceiling slabs were skimmed. Anyone got any tips on how to draw the nails without lots of ceiling cracks?

3 - I was going to use 4mm x 65mm screws - are these good enough?

Any other advice or tips greatly appreciated.

Thanks very much

gsxr1

gyppo wrote: »

Hi All,

I have a 25 year old bungalow with a trussed roof. Trusses are spaced 500mm apart. The previous owner had 8x4 sheets of 1/2" chipboard flooring the central section of the roof.

However, I want to remove the existing crappy sheets and replace with 3/4 2x8 osb t&g sheeting. The purpose of the floor will be only for light storage. I've never felt too confident on the existing chipboard stuff.

My questions are:

1 - will the 3/4 osb sheeting add additional weight/load on the roof trusses?
(note that below the central section of the roof trusses is a 4' wide hallway - I would presume the bottom section of the trusses are resting on this wall??)

2 - previous genius nailed the chipboard sheets instead of screwing them - though probably before the ceiling slabs were skimmed. Anyone got any tips on how to draw the nails without lots of ceiling cracks?

3 - I was going to use 4mm x 65mm screws - are these good enough?

Any other advice or tips greatly appreciated.

Thanks very much

You will be able to see it the joists are resting on a wall from above.

I would use the 24" wide boards which are T&G. They are easier to get up there.

Why not just nail on top of the old 1/2 inch stuff. Your trusses will be fine with the weight.

I would use a 4 x 40 mm screw. Less chance of screwing a pipe.

You will need a nailbar but be prepared for hardship as it is common practice to nail them with ring shank nails. You will probably get poppers and cracks below.

Sparkpea

I would suggest leaving the current boards in place and boarding over the top with 40mm screws also. Weight will be fine

gyppo

Thanks for the advice lads.

Regarding leaving the existing stuff there and sheeting over - theres no insulation under the existing chipboard, and I was going to insulate this area, so chipboard is coming up I'm afraid.

YouTookMyName

You could tap the nails into the joisting instead of pulling them, the chip board should break around the nails, might have less chance of cracking the ceilings.

Donadea Leo

Hi Guys,
had a bit of a disappointing visit from my friend over weekend. I had planned on doing the insulation on our attic and hoped to floor it and have it to a certain point in terms of converting it if necessary down the road.
My friend who is a roofer had given me a list of what I needed for quotes and had received a very good one. The plan was to screw on two sets of two by twos to the existing ceiling joists which were only 100ml. Cut and put in in 100ml Quinntherm between joists and roll over rockwool before flooring with OSB boards.

Got a really good quote on Friday and he came up to have a look at roof to make sure it was suitable before going on and ordering what I needed. His first comment 'oh didn't expect it to be a Truss roof' signalled there could be a problem. He hasn't worked with them before so said he'd find out if still possible or what would need to be done.

My own bit of research certainly suggests this is one for an engineer and certainly not something that can be done without a bit of expense more than I'd budgeted for.

My query is really how do I go about the insulation without having to undo it if deciding to convert in few years. I have had some quotes from insulation companies which are reasonable but they are planning to cover ceiling joists. I was hoping to maybe use a bit of space for storage so maybe go with the 2x2 idea and put down some OSB boards or use the insulated boards in certain places. I guess I don't want to make future work more complicated/expensive. Any advice would be welcome. sorry for bit of an essay.

Carlow52

A value-adding conversion in a trussed roof space is generally impossible so I would just insulate.
If the joists are only 100mm deep and u need to have storage space then u need to use the 2 by 2 idea a few times to allow u about 300 mm of insulation.
discard the notion of cutting rigid stuff:go with loose stuff: pm if u need a name of some stuff

brendankelly

Firstly none of the trusses can be cut. Under no circumstances allow any truss to be cut. If I was doing it (I am not advertising I am not a chippy) I would counter baton the new floor area with double 2 by 2s and use flooring boards. There will be less cutting in the long term and less waste and will be neater. I would use fibreboard insulation between the ceiling joists and sheep's wool between the 2 by 2s. The fibre board comes in 500mm sizes. I would use more fibre board between the rafters and finish it with I cannot think of the name but they are in every builders providers. Timber pre varnished in about 10 foot lengths about 100mm by 7 mm.

slimjimmc

gyppo wrote: »

Thanks for the advice lads.

Regarding leaving the existing stuff there and sheeting over - theres no insulation under the existing chipboard, and I was going to insulate this area, so chipboard is coming up I'm afraid.

One suggestion... cut some small openings in the existing sheeting, get loose insulation blown into the ceiling cavity (make sure it's compatible with PVC coated cables) then sheet over the whole lot with your choice of flooring?
Take special care if there are recessed lights, you must leave a sufficient clearance to avoid overheating/fire.

Donadea Leo

thanks for advice guys - value add won't be my consideration - may never need to do it but if family grows, might need to, so don't want to have to undo insulation work if we do convert. Only focusing on ceiling level for now and not going to touch rafters.
Would love sheeps wool but have 130 sq.metres of attic so out of budget.

hope this isn't hijacking someone else's thread, please let me know if so - is it ok to screw 2x2s into ceiling joists in a trussed roof (don't worry ,my wife has hidden the saw, so trusses are safe without employment of an engineer),

I'm toying with two options
I've seen the rigid insulation with the chipboard attached - what I saw was 75 mls which I'm guessing is equivalent to 75x3 = 225 fibreglass/rockwool . so fill between the joists with Fibreglass or rockwool and top up with this and then top up rest (ie outside walkways storage areas) with fibreglass/rockwool covering joists to 300ml,

versus

original plan of cutting rigid insulation 100ml which I guess should be equivalent to 300ml fibreglass and putting between joists after screwing in 2x2s, then OSB boards for walkway/storage, with perhaps further insulation on top (not 100% sure of this would actually be necessary at this stage) - I'm aware this is slightly trickier and will have to wrestle saw back off my wife. Also not sure if very kind builders supplier will offer me such a good deal when I revise my order.

there is a little bit of fibreglass half in there at moment - it's well shrunk down and a bit hit and miss in places, so was just going to leave it there and insulate over it.