Expansion joint in concrete floor question.

[NickE]

I have a large garage floor area under my house. I am in the process of making it into a clean and comfortable workshop and garage. The floor was badly laid, uneven concrete. I have used levelling compound to give a decent smooth surface and painted it with an epoxy paint (levelling compounds and paint don’t work well together except for very specific compounds and certain paints but that is another story!)

My problem is the expansion joints. The cowboys who built the house made a very poor job of laying the concrete to the degree that the three slabs are often 8 – 10 mm out of level and the expansion joints vary in width between 15 and 25mm. I have a total linear distance to fill of around 25m. The original joint was of the fibre board type of material and was broken, uneven and generally tatty.

I was going to use hot poured bitumen but because of the uneven levels I could foresee it running everywhere! I would also have to hire a bitumen boiler and the stuff is nasty to use.

I then found this excellent site and looked at the section on joint sealants. The two mentioned, Colpor 200 and Thioflex, seem of a higher specification than I need. The slabs are at an almost constant temperature all year and the movement will be minimal. I have lowered the top of the existing fibre joints and just need something to seal the joint and make it look tidy. Only two very short sections are going to be subject to the light use the floor is going to be subject to in the future.

Bearing in mind the uneven levels I would imagine a gun-applied sealant would be preferable to a pourable compound.

Any recommendations will be gratefully received.

[Tony McC]

Thioflex would be ideal for your project. I know what you mean when you say you're concerned about over-specifying, but in my experience, it's much easier to use summat like Thioflex than be messing about with a bitumen, and the results are more predictable.

Depending on how you're improving the existing floor, it may be possible to cut out the top 25-50mm of the flexcell fibreboard and patch the joint edges to give you a neat, straight, regular width joint, but even if you're stuck with what you have, Thioflex (or similar) would still be my sealant of choice.

[NickE]

Thioflex it is then!

I have removed the top of the fibreboard but the joints are anything but regular due to the obviously really poor shuttering in the first place.

With the work that I have done so far though I will end up with a clean, dust free and relatively smooth floor albeit with expansion joints the shape of a donkey's hind leg!

Thanks for your trouble in posting.

NickE.