Fitting a new patio door, should it sit in outer leaf or cavity area?

MegamanBoo

I'm looking to replace an old garage door with a pvc patio door.

The existing door is a timber frame and sits between the two leaves to close the cavity.

When I fit the door I want to raise the threshold by 100mm as I'll be raising the garage floor.

I've seen insulated threshold replacement products such as this https://www.prodomo.ie/thermal-brackets/ and they look great.

But elsewhere I've seen it's standard to fit these doors so the inside of the frame is flush with the inside of the outer leaf, so wouldn't that make these products redundant?

I think it might look nicer if the new door was sitting over the cavity, as the frame will be quite thick but other than that is there any advantage?

BryanF

Can you elaborate on the cavity? ~4’’?

Is the garage detached? is the plan to insulate floor/walls/roof?

is the plan to pump the cavity with insulation bonded EPS beads?

did you see the garage being built - are there cavity wall ties?

Assume there is a lintel or two above the door?

assuming inner leaf can take door straps, makes sense to keep it in the cavity. You should consider closing the cavity with rigid insulated board before adding the straps.

there are several threshold products on the market the route you go kind of depends on the list above, as those threshold products can be pricey.

MegamanBoo

Thanks Bryan, it's a 4 inch cavity half filled with polystyrene board and the remainder topped up with beads.

The garage is attached to the house and as it stands the timber door is letting a lot of draughts in. (We just bought the house, I'd have done something long ago)

Two lintels above the opening but I'm not sure about cavity ties.

I intend to insulate the floor but I'm limited to raising it by 100mm, above is a bedroom with some insulation in the roof, which I intend to improve in the longer term.

The threshold product I've shared isn't two expensive in comparison to the others I've seen.