Placing Expansion Joints/uncoupling Membrane

[On one]

Hi All
Just been and had a look at a 55m2 multi room floor job,with the Entrance floor,the utility floor and an orangery floor all running off from the kitchen floor.
Now normally I would put colour matching expansion strips under the doorways off the kitchen. But unfortunately some of these (new) doorways do not correspond with the edge of any concrete slab or brickwork cavity,so placing the expansion joint would become largely meaningless.
So do I try the best I can(fingers crossed) or is there another option......possibly anti crack matting?
Answers on a postcard to.......

 

[Rizzle from the Portizzle]

are there any exspansion joint already in the screed or are there exspansion joints all round the perimter

 

[On one]

No deliberate perimeter or concrete slab expansion joints.
But 2 of these new doorways are where walls have been knocked through,so there is a 75mm cavity to bridge as well.

 

[andy8758]

I use expansion joints from time to time across doorways between differing screeds. But I rarely see even perimeter expansion joints put in when builders lay a concrete base, let alone cross room joints.

I have in the past, on a really suspect screed (50m cracking across the room in several places covering water underfloor heating) used Ditra mat for the floor and cross room Dilex DWB joints on top (this was between support pillar in centre of room) as well as a joint across an adjoin room doorway). Overkill? Maybe but I couldn't afford to have the floor fail.

 

[On one]

I would have thought perimeter insulation/expansion joints would be a building regs necessity on new builds now. But that isn't the problem in my case,my problem is where to place the expansion joints and would uncoupling solve the problem.
P.S. Customer has just been on the phone and is wanting Electric UFH matting on SOME of the floor(on a concrete floor)

 

[Rizzle from the Portizzle]

I would have thought perimeter insulation/expansion joints would be a building regs necessity on new builds now. But that isn't the problem in my case,my problem is where to place the expansion joints and would uncoupling solve the problem.
P.S. Customer has just been on the phone and is wanting Electric UFH matting on SOME of the floor(on a concrete floor)

well that sorts it out for you screed in the cavitys .now you have a couple of ways to go .
you could use ditra heat or simalar as your decouplar or you could go over the floor with 6mm thermal boards to make sure the heat comes up .but also remember that every time you tile a job you have always put exspansion joints in .they are called grout joints and thats there whole point in uk build so how much exspansion do you need so lets surpose the floor is 12m2 x12m2 the tiles are 600mm x600mm 3mm grout joints you leave the tiles 6mm short of walls skirting to cover so how much exspansion have you left so far well it would be 72mm of exspansion .but did you leave a 3mm joint on top of the tiles but none on the bottom always measure the top of the tile and the back of the tile .some companys have made a fortune keeping this info to them selfs.and have made products .when only he truth needed to be out there

 

[Ajax123]

There is no rule for concrete sub bases but the general rule for screeds is that there should be a minimum 5mm compressible strip around the perimeter and to isolate columns and abutments. There should be movement joints at door thresholds and where bay sizes exceed the maximum recomendations (these differ for different screed types) and reflective joints over vertical movement joints in the sub base. When heated there should be movement joints between independently controlled zones and where heated meets unseated screed. Maximum bay sizes for heated sand cement should not exceed 6m and have aspect ratios less than 2:1. Anhydrite is more forgiving and bay sizes up to 20m with a maximum 6:1 aspect ratio are suitable. Additional joints should be considered at points of high thermal stress eg conservatories and cold stores.

 

[Rizzle from the Portizzle]

There is no rule for concrete sub bases but the general rule for screeds is that there should be a minimum 5mm compressible strip around the perimeter and to isolate columns and abutments. There should be movement joints at door thresholds and where bay sizes exceed the maximum recomendations (these differ for different screed types) and reflective joints over vertical movement joints in the sub base. When heated there should be movement joints between independently controlled zones and where heated meets unseated screed. Maximum bay sizes for heated sand cement should not exceed 6m and have aspect ratios less than 2:1. Anhydrite is more forgiving and bay sizes up to 20m with a maximum 6:1 aspect ratio are suitable. Additional joints should be considered at points of high thermal stress eg conservatories and cold stores.

could you exsplain the 2:1 6:1 aspect ratio to the lay men so over a 6m floor exspaion needed in mm and a 20m exspaion in mm is this in lm or m2