Garage floor-expansion joint-Builders pls advise

spurdog1

The house was built 1970. The wood inserted in the expansion joints have decayed, some bits left abt 50%.
To fit wood would probably be jammed in and probably stick out (I am only a minor DIY man).

To put cement/polyfilla would be tricky for me, and probably crack at the first hot summer.

How about some kind of spray mastic. Squirt in through a nozzle into the crack, wont have to be sized then?

What would be a good cheaper way (i'm retired)

Any links would be helpful Amazon and EBay.

Section62

spurdog1 said:

The house was built 1970. The wood inserted in the expansion joints have decayed, some bits left abt 50%.
To fit wood would probably be jammed in and probably stick out (I am only a minor DIY man).

To put cement/polyfilla would be tricky for me, and probably crack at the first hot summer.

How about some kind of spray mastic. Squirt in through a nozzle into the crack, wont have to be sized then?

What would be a good cheaper way (i'm retired)

Any links would be helpful Amazon and EBay.

You want something flexible and compressible - solid wood or mortar/filler won't allow the gap to close up.

The usual method is a solid foam or felt spacer topped off with a permanently flexible mastic sealant.

If the grove isn't too deep you probably only need the sealant.

spurdog1

from what i can tell, an inch wide, by about 4 inches deep. 25MM x100MM

stuart45

spurdog1 said:

from what i can tell, an inch wide, by about 4 inches deep. 25MM x100MM

You'd need a lot of mastic to fill that. You can get a 10metre roll of joint filler 100mm deep for around a tenner. Stick that in the joint and then mastic on top. 

spurdog1

where is the joint filler please?

stuart45

spurdog1 said:

where is the joint filler please?

If you Google miothene joint filler it should tell you the best place for you to buy it, such as Amazon, B&Q, etc. You can also use foam backer rods.

spurdog1

If we usre a bath mastic it won't gp far. i'm thinking expansive foam?

stuart45

Inside the garage isn't as important to get such a good seal on the joints. Outside concrete is more important to stop water getting in and undermining the concrete, and also freezing up an heaving.
So if you want to use just foam give it a go.

ThisIsWeird

Hi S'dawg.
Is the garage floor bare concrete? Painted?
By all means try expanding foam.
Brush/hoover out the slot, lightly spray with water to just dampen, and run your bead along the slot base. You'll soon judge a suitable amount to use
If the floor is nicely level either side, then a wee trick you may wish to try is to cut a long strip of polythene bag or sheet - from a bin bag will do - and lay this tightly over the slot immediately after injecting the foam, and adding a plank or timber batten on top - weighed down if it's a light plank to keep it in place. Or, wrap the plastic around the plank first, and then just drop it into place over the trench, with bricks or whatevs to hold it.
If you judge the foam quant to not be silly-excessive, this should be enough to limit its expansion, and give an automatic flat level fill, flush with the floor, and with a nice tough smooth skin. Once set, the plastic should peel away easily.
Much better finish, and a more dense foam-fill, than from just allowing it to expand out unhindered, and needing trimming off afterwards.
Best to paint it too, as most foams are not UV stable.

spurdog1

My thoughts towards concrete, it is my favoured choice, but if i concrete the expansion joint, i put the whole floor in danger of cracking???
the floor is bare concrete, no paint.

Section62

spurdog1 said:

My thoughts towards concrete, it is my favoured choice, but if i concrete the expansion joint, i put the whole floor in danger of cracking???
the floor is bare concrete, no paint.

As per my first post in the thread, if the joint has been designed to allow for expansion of the floor slab then filling it with a hard non-compressible material risks structural damage.  That may be limited to cracking of the slab, but could also result in the slab lifting.  Worst case is the slab then going on to cause cracking in the walls.

Is there a reason why you favour 'concrete' when the advice given in the thread so far has been the opposite?  What is it about the flexible solutions we've been suggesting that you don't like?