Quantcast

Stress load on c16 and c24 timbers

UKworkshop.co.uk

Help Support UKworkshop.co.uk:

Mutley Racers

Established Member
Joined
15 Jun 2017
Messages
155
Reaction score
2
Location
Molesey
Hi

I am wondering if anyone can help me. I want to understand how much force or weight in kilograms the above timbers can handle. For example, I want to install an accumulator in my loft which has 2 x 4 joists with a 3 metre span. The weight of the accumulator when full will be 200 kilos. How can i calculate this.

I also would like to install a sunken bath on the ground floor of my house with the joist being pretty close to 2 x 4's. As the bath would be close to the wall, i would need to cut out about 4 joists and add trimmers. Would the trimmers and sisters need to be doubled or tripled?

I hope that makes sense.

Thanks guys
 

MikeG.

Plodding on.
Joined
24 Aug 2008
Messages
10,134
Reaction score
620
Location
Essex/ Suffolk border
You'll need to wait for a structural engineer for your loft. For the bath, though, there are two separate issues: support for the bath, and the strength of the residual floor. I can deal with those.

If you are cutting a hole through a floor, assuming the floor is only bearing its own weight and not the weight of any walls, then you'll need to treat it in the same way as a stairwell. You need to double up the joists on either end of the opening.......and I mean double them along their entire length. Add in another joist alongside, and fix them together. Then the trimmer, which forms the long side of the opening will need to be a double, hanging from the doubled-up joists on hangers. Then the individual joists which you've shortened hang from that trimmer on hangers. I can tell you now that getting new full-length joists into place is a huge issue if you haven't got your entire floor up.

I can only assume from your description that you intend to sit the bath on the earth below a current suspended timber ground floor. You'll need to deal with A/ drainage levels, B/ air-flow issues to the sub-floor void, C/ forming a level base for the bath, D/ a proper seal around the bath because you have effectively created a hole in your bathroom floor through to the outside.
 

Mutley Racers

Established Member
Joined
15 Jun 2017
Messages
155
Reaction score
2
Location
Molesey
MikeG.":3oc0mlpk said:
You'll need to wait for a structural engineer for your loft. For the bath, though, there are two separate issues: support for the bath, and the strength of the residual floor. I can deal with those.

If you are cutting a hole through a floor, assuming the floor is only bearing its own weight and not the weight of any walls, then you'll need to treat it in the same way as a stairwell. You need to double up the joists on either end of the opening.......and I mean double them along their entire length. Add in another joist alongside, and fix them together. Then the trimmer, which forms the long side of the opening will need to be a double, hanging from the doubled-up joists on hangers. Then the individual joists which you've shortened hang from that trimmer on hangers. I can tell you now that getting new full-length joists into place is a huge issue if you haven't got your entire floor up.

I can only assume from your description that you intend to sit the bath on the earth below a current suspended timber ground floor. You'll need to deal with A/ drainage levels, B/ air-flow issues to the sub-floor void, C/ forming a level base for the bath, D/ a proper seal around the bath because you have effectively created a hole in your bathroom floor through to the outside.
Hi Mike, thanks for the info. Is the reason I need a structural engineer for the loft due to the weight of the roof?

With regards to the bath, I am able to get the fall to the drain as the soil stack goes through here close by. And you are correct in thinking I will be supporting the weight of the bath on the concrete foundation under the suspended floor so no weight on the joists.

The joists rest on honeycomb wall supports for the load bearing walls above. So I thought maybe I could scab to these. Or, maybe cut a hole in the side of the house and push joists through. And, put in supports from joist straight down to concrete slab.

If I could ask one more thing, related to joists. As I am a plumber who does do bathrooms, I want to get the best low profile shower tray possible. Preferably wetrooms formers. Now this is not always possible due to the position of tray to stack and floor joists run. Now I met a chippie who believe it or not mostly installs bathrooms as a job. He said to me that if you sister up your joists with ply either side you can drill a hole through them bigger than the stated 1/4 of the depth of joist in the centre. What are peoples thoughts on this?

Again, thanks for all the advice and time taken to reply.
 

Mutley Racers

Established Member
Joined
15 Jun 2017
Messages
155
Reaction score
2
Location
Molesey
Deadeye":ppv17pwo said:
https://www.roymech.co.uk/Related/Construction/Timber_Ex.html

Takes you through the calculations.
Thank you sir. A lot of calcs to get my head around there.
 
Top