Front door threshold?

[junglejim]

I’m building a timber frame house and am working on the front door detail. (We need to be part M compliant.)

 

 I’m having a custom timber door made as we want to add a unique stamp on the property. The door will come with frame but no hardware or threshold so I’m looking for advice on how to install and suitable threshold. We have a concrete slab and upstand which is level with internal screed so need to allow for ffl . I’m conscious of thermal bridging and the need to bring external paving to the threshold. We’re thinking of aco drain + paving slabs outside. The timber frame build up is as follows from internal to external;

 

- plasterboard

- 38mm batten

- foil insulation

- timber frame with pir insulation 140mm

- 9mm osb

- 38mm batten

- 20mm timber cladding

 

 the upstand matches the frame depth of 140 approx. 
 

It’s a detail I’d overlooked as originally imagined a timber threshold but realise I likely need aluminium or similar to meet part M. We haven’t yet screed internally and will be insulating the slab with pir so just trying to work out what I need, size allowances for door/frame etc and the build up needed.

 

 Any advice very much appreciated.

 Thank you

Edited September 16 by junglejim

[Redbeard]

I think we need a sketch or drawing, including the insulation detailing in the slab. Assuming the walls to rise from the slab (if not FFL) what stops thermal bridging straight through to the screed, level access or no level access? It sounds as if you need a thermal break, which has not been designed yet. I may have misunderstood, but a pic would be good. Something like Compacfoam (load-bearing insulation) springs to mind, but without a dwg I cannot suggest where or how you place it yet.

[junglejim]

Thank you @Redbeard

 We’re currently at slab level with timber frame erected and wind/watertight. Onto of the slab we will insulate with rigid insulation which I understand should also have a perimeter Insulation/expansion joint.

ontop of the insulation will be ufh, screed and then tiles to finish. Attached pictures are from  BC drawings but scope to adapt if needed.

 

 Any advice welcome.

 

[junglejim]

@Redbeardsee above 

[junglejim]

Just wondering if anyone can offer any advice on this? Thank you

[marmic]

we have used compacfoam under doors and in front of this an additional chamfered section (split due to dpc detailing). Bonded and mechanically fixed to masonry.  (I found it best to drill it slow with a wood bit - it melted and bonded to a masonry bit running faster!). Thick timber frame walls with doors set back.  Chequer plate aluminium over the chamfered bit tucking in under and sealed to the door threshold  Will probably have a decking bridge to bring us in level - shingle around house below this.  Or might do this with raised paving with drains under or on adjustable podiums - tbc.

 

do you have a vertical section through door?

[Oz07]

Last time I left 1 course of bricks out below dpc level at front door then was able to set cill below level of slab with a part m approved aluminium threshold level with slab

[Temp]

We have something like this (not my drawing). Any "steps" must be less than 12mm I think. I think our concrete sill is flat topped (no tiny step as shown below) with a 12mm high aluminium extrusion on top that the seal on the bottom of the wood door mates with. 

 

Edited 18 hours ago by Temp

[G and J]

On 25/09/2025 at 19:27, marmic said:

we have used compacfoam under doors and in front of this an additional chamfered section (split due to dpc detailing). Bonded and mechanically fixed to masonry.  (I found it best to drill it slow with a wood bit - it melted and bonded to a masonry bit running faster!). Thick timber frame walls with doors set back.  Chequer plate aluminium over the chamfered bit tucking in under and sealed to the door threshold  Will probably have a decking bridge to bring us in level - shingle around house below this.  Or might do this with raised paving with drains under or on adjustable podiums - tbc.

 

do you have a vertical section through door?

The spec I've got from our window supplier (who will also install) requires a concrete bit behind the single outer brick skin - are you using the compacfoam to structurally support the door frame?  If so that sounds a much better plan than a cast concrete bit?