Preparing floor for cill and new sliding patio doors.

[fandyman]

Hi,

I am trying to prepare the space for new cill and sliding doors. It used to be a one level surface before connecting living room with conservatory. I am trying to establish how to finish it ready for the cill and doors - should I be taking out the concrete with an angle grinder and exposing brickwork for new DPC and cill? The height of the concrete at threshold is 250mm and most of the cills are 300mm AFAIK. Could you advise I should be leaving it in place but just making it square or removing it further so that cill resides on bricks?

 

[phatboy]

Yes grind it to the correct levels, or a bit below so you can get a bed of mortar against the frame.

Cills are 30mm on PVC windows and doors, assume you mean that and not 300mm?! I'd cut 320mm if you are aiming for flush threshold inside, unless the door has a low threshold.

 

[fandyman]

Yes Sorry I meant to write 25mm and 30mm.

 

[fandyman]

The door is planned to be low threshold yes. I take it you meant 32mm then so I can have flush threshold?

 

[phatboy]

The door is planned to be low threshold yes. I take it you meant 32mm then so I can have flush threshold?

I got my units mixed up when I read yours! I’d cut to about 40mm, so threshold plus 10mm.

 

[fandyman]

Thanks. Which tools would you use for the job? This is my first job of the type so have just rough ideas of how to approach it.

 

[phatboy]

Ideally a 9" grinder, as you need to cut the thickness back of the frame. But if you haven't used one before they are a bit scary. A 4" grinder could be used, but would need to cut it a couple of gos.

Then a SDS breaker with a point bit, to remove the concrete.

 

[fandyman]

Thanks for advice.

What about circular saw with diamond/masonry blade?

 

[fandyman]

Would circular saw with masonry blade work here too?

 

[opps]

Would circular saw with masonry blade work here too?

The blade will be on the right hand side of the saw. The saw will not be able to reach the end of the cut (because of the saw base plate). You might still need an angle grinder.

I purchased the following, second hand from eBay.

Festool Diamond cutting system DSC-AG 125-Plus 230V online

Festool Diamond cutting system DSC-AG 125-Plus 230V â Unbeatable precision â Cutting building materials with minimal dust â Precise and clean â All information directly from the manufacturer ⨠www.festool.co.uk

www.festool.co.uk

But when used with the guide rail, its depth of cut is only 23mm, but it is idiot proof. It is basically like a plunge saw, you can set the depth and it runs along a track.

 

[fandyman]

I got my units mixed up when I read yours! I’d cut to about 40mm, so threshold plus 10mm.

Sorry I checked again the measurements (previously mismeasured).

So if the concrete slab height is 30mm and the recommendation is 40mm do you mean I should be cutting through the bricks below?

Another thing here is upon contacting the fabricator the door threshold is 50mm. Adding 30mm for the cill I am now looking at 80mm in total.

Wonder how low into the brick should I cut it now.

 

[phatboy]

If you want the threshold to be low, you need to cut however much you need really. So yes, cut down 80mm. Maybe check with the supplier first though. 80mm would be a hell of a step if you did nothing.