Thoughts on this

[ian158]

Bifold doors are four doors made from UPVC...about 1800mm

steer clear then, you that desperate for the agro it may become

 

[Sean SML Tiling]

if the joist get trimmed and become weaker they will also become more flexible and there's a good chance that the flexible adh wont cope. in my opinion joist are there for a reason and shouldn't be touched.

 

[Dougs Third Go]

I don't think weakening the floor would be too much of a concern in this instance. If they were taking lumps off the joists then yes but just in filling is not really much of a worry for me.

of greater concern would be the level of movement in the floor. Bear in mind that the joists will move at a different rate to the ply and if it is cut in really tightly it will try to belly when heated.

With trav this one sounds fraud with danger.

but you're actually taking the floor joists out of the equation. Assuming they're specc'ed to carry the existing floor if you batten to them the tensile strength will be reduced surely?

 

[Jeff the tiler]

It does not work. The joist are generally specified in relation the span of the area. Any adjustment will weaken them and you are increasing the load being put on them. Also, are you going to use a decoupling membrane, as this is going to ad further height issues.
Would love to see the joist after they have been reduced exactly by 18mm???
Just my observation

 

[Ajax123]

Joist are specified to carry a standard load plus a margin. The span is irrelevent in as much as it only affects he joist depth. they are usually designed to display a deflection no greater that the length divided by 300 or 12mm. When we put flowing screeds onto joists they are designed at L/333. in modern domestic housing this load is usually a minimum of 1.5kN/m2 but most builders architects and engineers over specify to future proof the dwelling. Most of the ones I come across these days are specified at 5kN which is a pretty hefty load. Provided the battens are attached at sufficiently regular intervals they will act compositely and the overall lad bearing capacity will not be appreciably affected. If the joists are add thinner then this will affect the load bearing but from reading your op this is not what is intended... Or have I read it wrong.

1.5kN = 1500N = 150kg per m2
5.0kN = 500kg per m2

 

[big george]

could you drop the joists?

 

[ian158]

Joist are specified to carry a standard load plus a margin. The span is irrelevent in as much as it only affects he joist depth. they are usually designed to display a deflection no greater that the length divided by 300 or 12mm. When we put flowing screeds onto joists they are designed at L/333. in modern domestic housing this load is usually a minimum of 1.5kN/m2 but most builders architects and engineers over specify to future proof the dwelling. Most of the ones I come across these days are specified at 5kN which is a pretty hefty load. Provided the battens are attached at sufficiently regular intervals they will act compositely and the overall lad bearing capacity will not be appreciably affected. If the joists are add thinner then this will affect the load bearing but from reading your op this is not what is intended... Or have I read it wrong.

1.5kN = 1500N = 150kg per m2
5.0kN = 500kg per m2

too much information !

 

[Gazzer]

I emailed client with my concerns and they just replied that they agree !!!!! they will now see if the joists could be lowered.........i am going to lie down now !

 

[Sean SML Tiling]

This job must be costing them a bomb. Most likely rip it up in 5 years as women get bored

 

[White Room]

I emailed client with my concerns and they just replied that they agree !!!!! they will now see if the joists could be lowered.........i am going to lie down now !

I can't see that happening, the work involved would be so expensive...

 

[Stef]

This is interesting as this was the way I was going to do my bathroom floor to keep the height to a minimum.
I was going to fix 4x2 or 5x2 along side the original joists, think they are 6x2, to strengthen the full floor.
Fix Marmox/Wedi on top, Ditra then heat mat, SLC, then tile.
Do you think this would be a viable option? 8/9m2 in total.

 

[charlie1]

This is interesting as this was the way I was going to do my bathroom floor to keep the height to a minimum.
I was going to fix 4x2 or 5x2 along side the original joists, think they are 6x2, to strengthen the full floor.
Fix Marmox/Wedi on top, Ditra then heat mat, SLC, then tile.
Do you think this would be a viable option? 8/9m2 in total.

no plywood? What will be your primary subfloor robby?

 

[Alan M]

we did a job a while back like this.
there was 9x 2 floor joists. we had to lower the floor by 2" for ply, tiles etc.
the span wasnt that big
we glued ,screwed and bolted 7 x 2" s to the side of the 9x 2"s then put noggings in every 3 feet and 2 layers of 18mm wbp overlapped , glued and screwed to everything
we got an engieer to give the ok. he said it was more than strong enough for anything they could put ontop of it.

i would want to see the builders work as they go along . and get a copy of the engieers report to cover yourself

 

[Stef]

no plywood? What will be your primary subfloor robby?

I would fit the ply between the joists.
The top if the ply would be flush with the top of the joists.

 

[Ajax123]

too much information !

Ooops!