flat roof repair / replace

FreeBear · 27 June 2024 at 11:43PM

wallofbeans said:

FreeBear said:

wallofbeans said:

FreeBear said:

The actual point of water ingress may not be anything to do with the flat roof. I see a downpipe to the right, so I'd be looking to see if there are any leaks soaking the wall down the side. Check for cracks and other faults..
Had a leak in my kitchen that took a while to identify the source. Tracked it to a crack in the main wall some distance from where water was appearing in the kitchen. Fixed the crack and patched the hairline crack in the render, and haven't had a problem since.

No leaks or damp patches on the walls. There isn't a down pipe anywhere near the point where the extension meets the main house either. You might be seeing pipes coming out of the bathroom on the right, but they are at least a metre back from where the extension connects - and the damp patch is on the other side of the room inside.

OK, so the damp patch is on the left - Would be worth looking over the top of the parapet to see if there is something amiss on the other side. There is some cracking in the render between parapet & main wall (on both sides), and it would pay to have a close look at the capping - Both potential weak points where water might be tracking in. You should also get the other cracks in the render fixed.

This all sounds helpful, if only I knew what words like "parapet" and "capping" meant.. any chance of a layman's terms version?

Is this something a roofer would spot and offer to fix?

wallofbeans said:

Kiran said:

wallofbeans said:

Kiran said:

Check the lead flashing is secure, and that the felt is lapped up against the wall underneath the flashing. The bell cast sits over the top of the flashing so double check there is sealant or mortar on top of the joint and no gaps. It looks to me that the bell cast has got some cracking too. How much water are you getting through? Are you talking about a damp patch or actual water running through? It would be worth getting some exterior masonry filler and raking out and patching the cracks and repainting and see if that solves the water ingress. The rest of the felt roof looks to be in pretty reasonable condition

It's a minor damp patch - never had any water running through at all. Just noticed water mark patch of about 30cm long on the join between extension flat roof and end of original building.

If its a minor damp patch I'd go with the render cracks, but take a look at any motor joints on the cappings etc. too. Rake out the cracks and reseal with exterior grade filler and repaint. Monitor the issue and see if it reappears.

If you want to do a proper investigation you can water test the areas one at a time and see if you can force the leak. start at the lowest point working upwards but with it being a damp patch Id look at the first option first and see if that solves it.

I've had a similar issue, previous owner built an extension and I was getting water ingress but more severe than yours by the sound of it. It should have had cavity trays and weep vents installed above the extension roof. Moisture was getting down the cavity and making the ceiling damp. I've refilled the cracks and sealed up the flashing joint and it appears to have worked so far.

Again, really helpful.. if only I knew all the terminology... Can you explain what "motor joints" and "cappings" are?

Cappings (or to be correct, coping), as per picture above.

motor joints is a typo - It should be mortar joints. Mortar is a mix of sand and cement (or lime on older properties) used to stick the bricks together. Think of it as the glue holding all the parts of the wall together.