Re-bedding concrete ridge tiles

[wobbly2]

Can anyone advise an acceptable/ best way to joint the gap between Sandtoft half round concrete ridge tiles on a garage roof. The gap between the tiles is only about 2mm (unless one is cut down). The roof rafters (welded steel) spacings are excessive which I would imagine means the roof will flex a lot, especially while the ridge is being refitted.

A friend suggested using silicon sealant but I’m not at all comfortable with this unless it’s classed as an acceptable method that would have good longevity

Any help would be much appreciated, many thanks.

 

[mfarrow]

Most ridge tiles leave a gap. You need to fill the join underneath with mortar and point on top.

Make sure you're using suitably strong mortar. 1:3 is standard.

 

[wobbly2]

I believe that a 2mm gap between ridge tiles is insufficient to use mortar and a more flexible solution should be used; but what? It appears that (likely) flexing of the roof, due to excessive distance between supporting joists, means that even if mortar were used no lasting bond between tile and mortar would be achieved. Also, flexing of the roof while the ridge is being laid would quite likely break the (wet) suction bond between tile and mortar as the work progressed; meaning the ridge would potentially leak even before it had time to set/dry.

Presumably bedding the ridge tiles on mortar would be OK, as any flexing is more likely to break/crack the bedding below the gap between the ridge tiles and any water ingress would seep through the crack onto the mains tiles beneath. Looking around I've seen several ridges where the mortar bedding has cracked at the tile joints, presumably with the associated ridge tile gap also cracked.

Re pointing - I've read in a tile association/manufacturers website that the mortar used to fill the gap between ridge tiles should not be pointed as this will push the mortar away from the underside of the tile thus ensuring no bond is achieved other than on the tile side edges.

 

[mfarrow]

Have a look on YouTube. You shouldn't point/joint straight away anyway, wait an hour or so for the mortar to go off then just go over with a jointing tool.

 

[wobbly2]

Have a look on YouTube. You shouldn't point/joint straight away anyway, wait an hour or so for the mortar to go off then just go over with a jointing tool.

When you say "jointing tool" do you mean pointing iron? I'm aware of how to point mortar using an iron or trowel but neither of these is going to help if the gap between the tiles is too small to use mortar in the joint; plus flexing of the roof whilst kneeling on it will most likely causes the mortar to pull away as I move about on the roof anyway.

 

[^woody^]

Any pointing will fall out again very soon. They need to be re-beded and then the joint tooled smooth.

 

[mfarrow]

Yes half-moon jointing iron, bucket handle or whatever. I just used it to smooth off. Try it and see. If you don't want to just leave it however you like. You seem to have made your mind up.

 

[^woody^]

Have a look at Fischer Express Cement, which is essentially mortar in a tube.