Is my loft joist strong enough

river_kwai

The joist in my loft is 35mm by 100mm. The gap between two joists spans 560mm. I have bought 1220x325x18mm loft panels. My question is that is my loft joist strong enough for boarding the loft? I am planning to board an area about 20 sq meter.

nielingren

why are you boarding? are you going to put stuff on it.

and the next thing is i think they are about the same size as mine and there i lots of stuff up in the loft but how meny walls are there wats the span?

river_kwai

The are not many walls below where I am planning to board up. The airing cupboard and built-in wardrobes and walkway to ensuite shower rooms are the walls underneath where I shall be boarding (but they stud walls). I am hoping that the joist would be strong enough to hold the 18mm loft panels and some of my stuffs, like Xmas decor, extra clothes, winter jackets, etc. I won't be storing magazines though as I am afraid they might be too heavy.

woodbutcher_2

I did that in my last house and had a permanent crack in the front bedroom ceiling.Filled it loads of times but it kept cracking.I am about to fit a loft ladder in my new house but will try and store stuff above supporting walls.

lush_walrus

river_kwai wrote:

The joist in my loft is 35mm by 100mm. The gap between two joists spans 560mm. I have bought 1220x325x18mm loft panels. My question is that is my loft joist strong enough for boarding the loft? I am planning to board an area about 20 sq meter.

Ok, to give you an idea generally floor joists are either 175mm x 50mm or 225 x 75 at 600 centres, which are sized to take the constant loads of furniture and the weight of people. The size you have in your loft are pretty typical and are not able to actually take a heavy constant load. As long as you do not pile everything you own on top of them they should be ok. But as above it could well lead to cracking in your ceiling below.

river_kwai

lush_walrus wrote:

Ok, to give you an idea generally floor joists are either 175mm x 50mm or 225 x 75 at 600 centres, which are sized to take the constant loads of furniture and the weight of people. The size you have in your loft are pretty typical and are not able to actually take a heavy constant load. As long as you do not pile everything you own on top of them they should be ok. But as above it could well lead to cracking in your ceiling below.

My concern is that will it lead to more than just cracking, ie more severe structural problems.

lush_walrus

river_kwai wrote:

My concern is that will it lead to more than just cracking, ie more severe structural problems.

It won't lead to severe structural problems as such as nothing is taking its support from the joists. Above is the roof that will be supported via rafters and tied in via wall plates. Below is the ceiling, which will be supported by the joists above (ie the ones you have measured in this position).

Worst possible scenario, the joists will fail and that area of ceiling will collapse, which in itself is quite expensive to fix (via new joists, plasterboard and the electrics etc for that area re-wired), but is likely to be isolated to that area.

woodbutcher_2

The rafters serve two purposes.To carry the ceiling below but more importantly to stop the roof spreading.You should be ok if you are sensible.

nelly_2

at 35 mill it sounds like roof trusses to me.

either way id be suprised if you mange to break them

river_kwai

nelly wrote:

at 35 mill it sounds like roof trusses to me.

either way id be suprised if you mange to break them

no, it's definitely the joist that I measured. 35mm wide! The house was built in 2000, I would say modern house are definitely built with as least material as possible to cut cost, am I right to say that.

A chat around the office reveals that most colleauge has loft joist of 50mm with a distance between the joists of half what I have in my loft!

plumb1_2

river_kwai wrote:

no, it's definitely the joist that I measured. 35mm wide! The house was built in 2000, I would say modern house are definitely built with as least material as possible to cut cost, am I right to say that.

A chat around the office reveals that most colleauge has loft joist of 50mm with a distance between the joists of half what I have in my loft!

They are actualy part of the roof trusse, even though people call them cieling joist.
If you were to cut all the cieling joists out your roof would collapse

http://www.roof-trusses.co.uk/UploadedFiles/TechnicalInfo/pds2.pdf