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Posted: Tue Feb 24, 2009 7:01 pm
by sharpie
Bit off topic for the site I know but I would appreciate some advice on internal floor screeding.
What mix of sand, cement (plasticiser?) should I use and how do I estimate quantities? - my floor is about 4x4m with a screed depth of about 80mm.
Is this within DIY scope and do I need any particular tools other than regular trowels, float etc?
Anyone know of a suitable diy guide here or elsewhere?
Many Thanks
Posted: Tue Feb 24, 2009 7:43 pm
by DNgroundworks
Well you could use a concrete screed, at a 6-1 ratio ie 6 sand&gravel and one cement.
(sand and gravel is available from most merchants premixed)
Or you could use a grano screed and again the same 6-1 ratio.
But before hand id dampen the floor off, and prime with a slurry mix and stiff brush applied ( slurry mix - just cement and water mixed very wet brushed on to the floor before applying the screed)
No plasticiser.
Well id say youd need about 1.5 tonnes of watever you choose to lay.
Hope this helps.
Posted: Tue Feb 24, 2009 7:45 pm
by DNgroundworks
Also tools needed, shovel, trowels, screed bar ( can use length of timber), level, stiff hand brush, barrow, mixer.
Posted: Tue Feb 24, 2009 7:58 pm
by msh paving
Sorry to disagree DNgroundwork but floor screed is 3-1 sand and medium sharp sand or sharp sand no gravel, MSH 
Posted: Tue Feb 24, 2009 8:58 pm
by lutonlagerlout
3:1 screeding sand : cement
the definition of screeding sand varies greatly ,but it generally will have some grit in it up to about 5mm and a lot of sharp sand (angular grains)
LLL
Posted: Tue Feb 24, 2009 9:01 pm
by DNgroundworks
Why 3-1 on internal work? whats the need for that strength of screed?
Posted: Tue Feb 24, 2009 9:11 pm
by msh paving
Floor screed has always been 3-1,anything less wont take the wear,any readymix screed is always 3-1
Posted: Tue Feb 24, 2009 9:11 pm
by DNgroundworks
I disagree with the no gravel too, 80mm of 10mm stone concrete should be fine as long as it is well bonded to the underlying surface.
What is the underlying surface?
Posted: Tue Feb 24, 2009 9:13 pm
by DNgroundworks
What wear? by the sound of it, it sound like its in his front room. If it was a screed in a garage and the like yes i agree 3-1.
Posted: Tue Feb 24, 2009 9:14 pm
by msh paving
gravel in a semidry screed will not finish with a tight close surface brush it when dry and gravel will brush out,the only thing to make it stronger is put a layer of chicken mesh mid way
Posted: Tue Feb 24, 2009 9:16 pm
by msh paving
door openings will get foot traffic even under carpet,6-1 wont last 6 months
Posted: Tue Feb 24, 2009 9:17 pm
by lutonlagerlout
i been on building sites for 25 years DN and floor screed has been 3:1 for all that time,maybe a patio could be done at 6:1 ,but all the jobs i do it always specifies and i quote" 70mm of 3:1 floor screed"
i have seen it done weaker and it drys out and breaks up very easily,remember there is very little water in floor screed
LLL
Posted: Tue Feb 24, 2009 9:19 pm
by DNgroundworks
Chicken mesh mid-way will not prevent stone brushing out of the surface, it is possible to get a tight closed finish with proper troweling.
Posted: Tue Feb 24, 2009 9:24 pm
by DNgroundworks
Well the lads ive had in to do all the screeding in my house have done it this way, and its fine, and this was over 2 years ago.
Just think 3-1 is a bit over kill but anyway....
Posted: Tue Feb 24, 2009 9:27 pm
by msh paving
the chicken mesh is for reinforcement to stop cracking and shrinking ,you will find it very hard to finish semi dry screed with stone in ,i have never seen a floor screed semidry with stone in it,