Question about using a magnesium float on a garage floor pour last Tuesday. The finish came out way too open and porous.

It was a 30 yard pour for a two car garage. I switched from my usual aluminum darby to a brand new magnesium float after the bleed water was gone, thinking it would give a tighter finish. The surface ended up looking sandy and rough, almost like it sucked the fines out. The homeowner in Boise was not happy. Did I use it at the wrong time, or is magnesium just wrong for that mix design? What's the trick here?

3 comments

3 Comments

uma65916d ago

Check the actual air temperature that day. A mag float can pull moisture out too fast if it's hot and dry, leaving that sandy look. You might have been fighting the weather more than the tool.

hayes.wade16d ago

You switched to a brand new magnesium float on a 30 yard pour. That's your first mistake, they're way too aggressive right out of the wrapper. You basically sanded the surface with it. You have to burn a mag float in on a couple smaller jobs first to knock the sharp edge off the blade. You pulled all the cream right to the top and left the aggregate exposed.

garcia.mila16d ago

That's a common tip but I've never had an issue on big pours. The key is keeping the float flat and using a really light touch on the first pass. If you angle it even a little, sure, you'll cut in. I always use a new one straight from the supply house for a finish this size.