On concrete

[plow]

Is their a "flatness standard" on new pours? Slab will be 40x60 with a 60x 15 apron. The apron will be sloped slightly. Thanks.

 

[brownbagg]

yes, depending on what you want

 

[plow]

I weld alotta stuff on the floor. Not looking for perfectly flat, just flat.

 

[Daniel Dudley]

A quarter inch is considered good by many. Getting within an eighth is hard for most.

If you have special requirements, you need a real pro.

 

[ConCretin]

The standard measure for many years was to lay down a 10' straight edge and measure the gaps between it and the floor surface. A floor with gaps less than 1/4" is better than average and would be a reasonable standard to shoot for. You obviously want to let the finishing crew know up front what you expect.

 

[GYPSY400]

Most good finishers should be able to get it reasonably flat.. Not like some of the horror stories you see here on GJ.
My floor is done really well except one corner is a little low.. But that is in the compressor closet so I'm not concerned.


I also had them make the floor taper 2" from outside edge to centre for water drainage.. A bigger floor will have to taper more


Sent from my iPhone using Tapatalk

 

[larry_g]

I weld alotta stuff on the floor. Not looking for perfectly flat, just flat.

Make sure that you understand the difference between flat and level. A wall is flat but not level. If you want flat then spec a variance of say 1/8" in 10' in the contract. Then you have to have a procedure to be able to measure and prove that the spec has been met. Have this in place so it is part of the contract. For me I wanted level as this is a shop not a parking garage that is subject to daily snow filled cars dripping. So I had to convince the concrete guy that and check it with the laser level.

ON Edit; looking at the size of your building you may want to consider figuring out where your fab work is to happen and only have a tight spec on the finish in that bay and let the areas of storage and parking run looser, saving money maybe.

lg
no neat sig line

 

[plow]

Make sure that you understand the difference between flat and level. A wall is flat but not level. If you want flat then spec a variance of say 1/8" in 10' in the contract. Then you have to have a procedure to be able to measure and prove that the spec has been met. Have this in place so it is part of the contract. For me I wanted level as this is a shop not a parking garage that is subject to daily snow filled cars dripping. So I had to convince the concrete guy that and check it with the laser level.

ON Edit; looking at the size of your building you may want to consider figuring out where your fab work is to happen and only have a tight spec on the finish in that bay and let the areas of storage and parking run looser, saving money maybe.

lg
no neat sig line

Excellent idea. That's what I'll do, Take a space, say 40x30 and make the rest "standard or average". Thanks guys

 

[radrush]

If you want flat then spec a variance of say 1/8" in 10' in the contract.

This measurement can NOT be specified because it can NOT be measured. Because of a myriad of fallacies this type of spec was abandoned decades ago (35+ years ago).

READ this: http://www.concretefloors.ca/fno.htm

and this

http://faceco.com/40q.html

The correct spec and test for randomly trafficked floor surfaces is per ASTM E1155 - 96(2008) - the Standard Test Method for Determining FF Floor Flatness and FL Floor Levelness Numbers.

You have to specify how flat and how level you want the finished slab. A good flat/level floor for commercial garages would be 38/25.

However, residential concrete finishers are not good enough to meet this fairly low basic requirement because the types of slabs they finish are too small to utilize the two pieces of equipment needed to produce a flat/level slab: a heavily weighted highway-screed and 10'-wide double pan float machine.

I use the pictured device (a $10K FloorPro) to determine if my clients are getting the floor that they are paying for.