How to fill 22 cm diameter hole in concrete roof?

Joined
19 Feb 2015
Messages
690
Reaction score
4
Country
United Kingdom
I have a flat cast concrete roof (10 cm thick) on an outside shed.

There is a 22 cm diameter hole punched through it from a previous boiler flue - no longer there.

How would I go about filling this is? I don't want to botch it so if someone ever walks on it in the future they don't injure themselves by putting their foot through it.
 
Sponsored Links
Why do you want to fill it? Safety/weather tightness/aesthetics/warmth?
Since no one else has replied, I'd probably drill some holes at an angle from below, insert plugs and long screws hanging about half way into the hole (like a fake rebar) then shutter underneath with ply and pour in some reasonably strong mix concrete but as dry as possible to aid water tightness. I'd fill to proud and trowel a smooth fall to the existing roof to keep it dry.
Then leave a couple of days and remove the shutter
Your issue there would be cracks around the edge letting water through.. Other option is just put a roof tile or slate over at an angle to deflect the water.
Hopefully someone else well be along soon.
 
Perhaps just put a strong (galvanized) steel plate over the hole, overlapping the hole and bedded on mastic?
 
Because the hole is so big, I would do similar to what John D has suggested, a damp mix concrete shuttered from below, however I would scabble the side of the hole first with a scutch chisel to give a mechanical key.
 
Sponsored Links
Thanks for the replies. I'm sure I'll get something sorted from this.
 
Take a piece of board large enough to cover the hole from underneath, and find a piece of wood that'll wedge it in place. Fill the hole from above with a bag of balast from wickes, mixed with cement in about 1:6 ratio (cement to ballast). Wet the insides of the hole before you pour in the concrete mix, and it should set overnight, and allow you to remove the board from underneath and smooth it off before it's gone off comletely - it won't be pretty, but it'll do the job.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top