I've tried to JFGI but have had no success so thought I'd ask here.
Probably just a hypothetical question but, looking for a replacement
timber door, I see that some are 'Part L', as in they have a low enough
U-value to satisfy some arbitrary rule that most of us ignore. (And
quite within the rules if the frame stays in place.)
Most of them pretty unattractive and none of them what I need, but I got
to wondering how they're built to achieve that status. There's not much
room to fill a door with PIR or something, but maybe that makes enough
of a difference. Would have thought that would make them a bit
light-weight though for an exterior door.
Any ideas folks?
Interesting selection, but they all seem to be composite or steel. I
can imagine ways of insulating those materials effectively, but it's
timber I'm particularly interested in as if I (or anyone here really)
wanted to build one from scratch, timber is the likely material of choice.
On Wednesday, December 4, 2013 10:00:16 PM UTC, GMM wrote:
I got CB approval by calculating the insulation of the door I proposed to make and submitting it. The proposal was a sandwich containing Celotex but was made to match the doors elsewhere in the house.
email me on laws at bcs dot org uk if you'd like me to send you what I sent them.
This is one I made.
Essentially a timber frame filled with rigid foam.
The face could be any material/thickness you want for security.
On Wednesday, December 4, 2013 7:42:28 PM UTC, GMM wrote:
Will it have DG and be subject to horizontal rain, particularly wind driven
If so, get / make a door which has proper drain holes at the bead base (5-6
mm as I recall), a correct drain profile (5 degrees as I recall) and uses a
glazing spacer to lift the DG panel out of the wet area?
There is a BS standard covering this, and countries such as NZ and others h
ave detailed design documents from their own testing.
Otherwise you may find water coming through the internal bead and your nice
engineered door swelling and leaking all over the place. I know :-)
Making your own is not that difficult - I plan on doing the same, going fro
m 44mm to something deep enough to get a bit of celotex or XPS in the lower
panel. Shockingly the lower panel on some is so thin it just runs in water
when the humidity is actually quite low, really really thin stuff.
I guess the most waterproof door would be a very thick one (60mm?) with a S
G outer (set in whatever putty substitute) and a DG inner which is removeab
le should the need arise. It would eliminate all the nonsense and achieve T
ripple Glazed (TG).
For some reason the TG I have seen, even in timber, always use a DG outer a
nd SG inner. Considering the inevitable issues with sealing/draining timber
DG I would have thought SG outer was better. Perhaps it is for security or
You can change the door-only under Part L, and there is a <50% glazed area
rule too. I am not sure you can change the frame-only when that frame compr
ises a glazed portion (eg, replace all the timber components with deeper to
permit celotex in large timber areas without either getting ugly inside or
outside re surface locks and hinge positioning.
On 06/12/2013 21:47, firstname.lastname@example.org wrote:
The one I have in mind (if I tackle it) is actually well out of the
weather as it's between the back of the hallway and the conservatory, so
it wouldn't see any rain. The conservatory, which is ultimately on the
list for improvement, gets down to outside temperature pretty swiftly as
it's very well ventilated, and it's clear that we lose significant
amounts of heat by that route.
Of course, a good part of the problem would be cured by any half-decent
new door, as the existing one is slightly warped so has proved difficult
to draught proof. Naturally, nobody sells a door that's a good match
for it in the size, which is what got me thinking about the possibility
of building one. In that case, it would make sense to make it as close
to well insulated as possible. I'm not really concerned about the
rules, as nobody would ever know I had changed it in a position like
that, but they do provide some useful targets to aspire to.
I'd be interested to see how you get on, please post back if you go
ahead. I have similar plans in mind but for a laminated security door
rather than an insulated one. My biggest concern is the long term
stability of the build, I don't want to go to all that bother and then
have it warp by even a couple of mm.
If you were to use 10mm WBP ply outer skins then you would have room for
an inch of celotex within a 46-48mm standard beefy door. As well as a
solid border and beefy fills for locks and hinges I'd suggest an
internal cross or similar made from edge on battens, bonded and fixed
through to join the skins to enhance rigidity and hopefully stability.
If you've had trouble with draughts then the laminated construction
would lend itself to making it a rebated fit with double seals, one
against the main door face and one against the rebated one.
Not something I have come across before, interesting thank you.
In summary, about 55% more effective per unit thickness than PIR foam.
Expensive which is not surprising considering how it is made but it will
limit its use to specialist areas. Let's hope it becomes cheaper as it
becomes more mainstream.
For the door app, a single layer of 10mm Aerogel would be about 60% as
effective as 1" celotex and cost about 40quid, with two layers being 25%
more effective but costing 80quid.
My external doors here are 48mm so I'd prob stick with a celotex core
but 20mm Aerogel would either allow a thinner door or the use of beefier
12mm ply skins to make 44mm overall.
I recently made something like this; I needed a door for the garage I'm
(slowly) converting into a workshop and it was not a standard size.
Because the workshop is not ready yet I only had limited facilities -and
I made the outline from standard size timber 38mm thick with 3
horizontal members and 'Z' bracing from narrow strips of wood. I put a
triangular gusset where the lock would be fitted. I used dowel joints -
(limited skill and facilities)' I faced both sides with 5.5 WBP ply and
fixed this with drywall screws at 3" spacing all round the outer edge
and into the horizontal and diagonal members. I drilled a number of 20mm
hole in the inside skin and used them to inject expanding foam into the
It has been up for 6months now and, touch wood, seems to be
If I was doing it again, I would probably use thinner ply for the skins
and would try to find some marine ply at a reasonable price.
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