Loft Conveshion/flooring To Office Space help?

[watson49]

Please can you help me I am converting my loft into a small office as im losing my office to my newborn child. Understand that I will only be up there 1 day a week for work purposes and will only have a desk and a chair up there really of any weight.

I know the sealing can take the it as 3 of my neighbours did this years ago and one of them have a teenager leaving up there.
My questions are:
Should I use 2.400x600x18mm tongue and grooved chipboard or 2.400x600x22mm?
I was going to use the smaller ones but there not so good at taking the weight from what I heard?
Should I use P5 water proof or is this a waste as I have never had a leak up there?
I currently have fibre glass installation down. Now should I squash this down under the new boards?
I will be putting up new insulation in the upper walls when I board them later on but do not want to waste what I already have?
Any help you can give will be helpful.
Thank you

 

[Burnerman]

18mm T&G chipboard will be just fine so long as your joists have standard spacing....but you don't tell us what section of timber the joists are?
John

 

[watson49]

The Joists are 45cm apart and 2x4 inch thick. doubled up in some area's to 4x4.
the attic itself is 33.64 M2.
7 foot high in the middle.

 

[watson49]

also there is a load baring wall right though the middle underneath it.

 

[Burnerman]

Sounds like thats just fine then....compress the insulation below the boarding so you don't bulge the ceiling below, or your new boards above and all will be well.
John

 

[watson49]

Sounds like thats just fine then....compress the insulation below the boarding so you don't bulge the ceiling below, or your new boards above and all will be well.
John

Are you sure though as some people have been saying that I should make my joist's bigger.
Did have a builder come over and they said it was ok but im not sure about there qualifications.

 

[Burnerman]

Your joist spacing - the traditional 18" - and joists themselves of 4"x2" will be fine for your proposal in my opinion.
I've seen loft joists of much feebler proportions grossly overloaded and they've stood up fine - albeit with some cracking of the ceiling plaster underneath!
If you've any worries or doubts, concentrate the intended load over the area that is around the supporting wall.
Fix the boards down with screws - you don't need hammering of nails up there..... I would suggest 45mm x 5mm screws to hold things nicely.
Use a 'flip driver' - pilot drill one end, screwdriver bit on the other - and the job will be done in quick time.
John

 

[tony1851]

they've stood up fine - albeit with some cracking of the ceiling plaster underneath!

So cracking of bedroom ceiling plaster is fine is it?

 

[watson49]

Your joist spacing - the traditional 18" - and joists themselves of 4"x2" will be fine for your proposal in my opinion.
I've seen loft joists of much feebler proportions grossly overloaded and they've stood up fine - albeit with some cracking of the ceiling plaster underneath!
If you've any worries or doubts, concentrate the intended load over the area that is around the supporting wall.
Fix the boards down with screws - you don't need hammering of nails up there..... I would suggest 45mm x 5mm screws to hold things nicely.
Use a 'flip driver' - pilot drill one end, screwdriver bit on the other - and the job will be done in quick time.
John

The Desk will be on the load baring wall and will not have anything else up there but myself so should be ok. thanks for the advice. I know it may have some problems in a few years but this is only to last a year or 2 untill I have the cash to do it all properly. thanks again.

Please let me know if you thinks of anything else.

 

[watson49]

If I was to reinforce the floor first what what you recomend.
Sistering? if how with what timbers? and how much do you think it would cost as I think I would get somone else to do it?

 

[tony1851]

If you're not putting too much weight up there, just screw and glue some 2x2 battens along the tops of the joists. Use a 3 1/2" 12s screw every 12-14".
You don't have to go rightinto the eaves - a foot or two short will do. Finish with 18mm chip. Keep your load within about 3 or 4 ft of the loadbearing wall (which you will anyway because of headroom).

 

[watson49]

If you're not putting too much weight up there, just screw and glue some 2x2 battens along the tops of the joists. Use a 3 1/2" 12s screw every 12-14".
You don't have to go rightinto the eaves - a foot or two short will do. Finish with 18mm chip. Keep your load within about 3 or 4 ft of the loadbearing wall (which you will anyway because of headroom).

Thanks for the advice