Cold bridging - door threshold and doorstep

[drpepe]

Hi we have a condensation / damp issue involving condensation forming on the front door aluminium threshold and the inside of the concrete (?) doorstep. The problem didn't start til the weather changed this autumn.

This pic shows condensation that has formed on the aluminium threshold
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Condensation dripping off the inside of the doorstep in the doormat well:
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The doormat well problem area. As you can see it is a bit of a mess (until recently it was ful lto the brim with dirt and rubble and had no ventilation)
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Possibly the issue is exacerbated by:
The general under floor dampness - slightly damp soil and little ventilation until recently. I dug out the hall subfloor and put an airbrick under the doorstep in the pic a couple of months ago. Rel humidity in the hallway is constantly 60-80%

The doormat hatch is very poorly fitting, meaning the concrete step is exposed to humid warm air from the house. - we hope to reboard the entire hallway with a close-fitting hatch, so will hopefully make the doormat well and subfloor more 'airtight'.

Q/ Would replacing the threshold with another material - eg. upvc reduce bridging via the threshold strip?

Q/ Any suggestions regarding the doorstep condensation? The floorboards are pretty rotten in contact with the doorstep. Part of the hatch frame was previously screwed to the inside of the step and was totally rotten - hence the bricks inside the mat well currently being used to support the hatch. Is it at all possible to insulate the inside of the step so that it isn't in contact with the interior woodwork (it is quite an awkward area) ?

 

[drpepe]

Any comments on how to reduce the doorstep condensation that is causing my floor to rot??

 

[lbzbean]

What is the temperature in the hallway? What is the temperature of the condensing part of the doorstep?

Just trying to see how much below the dew point it is, then we could see how much of a problem you've got.

 

[AronSearle]

Can't see anything you can do, cold bridging is eliminated by insulation, where do you expect to put insulation?

You can try to ventilate locally around the area, but short of drilling holes or removing draught seals (probably a bad idea), I can't see how that will work.

Buy a non crappy aluminium door, sorry?

 

[Gazman16]

Can't see anything you can do, cold bridging is eliminated by insulation, where do you expect to put insulation?

You can try to ventilate locally around the area, but short of drilling holes or removing draught seals (probably a bad idea), I can't see how that will work.

Buy a non crappy aluminium door, sorry?

Thats a Composite door with part M compliant low aluminum threshold.


I have fitted about 100 of these doors and yes you can get a bit of condensation on the Ali parts but I dont think that will be causing your problems.

Is it as wet as it looks in that hole?
I would be checking the pipes for leaks, Making sure its ventilated under there. Make sure the steps are sealed on the outside.

 

[drpepe]

What is the temperature in the hallway? What is the temperature of the condensing part of the doorstep?

Just trying to see how much below the dew point it is, then we could see how much of a problem you've got.

There is a radiator immediately to the right of the door, but there is an airbrick in the doorstep and floorboards and hatch are quite gappy so the temperature is 'normal' room temperature minus a bit. ie. 17-18degC on an evening at the moment (i have a thermomoeter/hygrometer in the hallway).

THe problem seems to be that the concrete step is basically outside temperature - ie. close to zero at this time of year. Hence the winter condensation problem... there is no condensation anywhere else in the house.

Can't see anything you can do, cold bridging is eliminated by insulation, where do you expect to put insulation?

You can try to ventilate locally around the area, but short of drilling holes or removing draught seals (probably a bad idea), I can't see how that will work.

Buy a non crappy aluminium door, sorry?

Ha - well we had almost exactly the same model door in our old house, but no problem at all.

Ok, so the aluminium threshold aside, we still have a problem with the interior of the step..

When the floor/hatch are rebuilt there will be less warm & humid air hitting the cold concrete. However as you can see in the pic there is a strip of the step that is above existing floor level.

I was wondering if it was worth waiting until summer (so it dries out) and then coating the exposed (or all) of the inside of the step with something - painted on or stuck on - again to stop humid air hitting it.

What I don't want is to get a load of new wood in there and it all rots in a few winter's time...

Thats a Composite door with part M compliant low aluminum threshold.


I have fitted about 100 of these doors and yes you can get a bit of condensation on the Ali parts but I dont think that will be causing your problems.

Is it as wet as it looks in that hole?
I would be checking the pipes for leaks, Making sure its ventilated under there. Make sure the steps are sealed on the outside.

Thanks for confirming that there isn't anything obviously dodgy about the aluminium threshold. I wonder whether it could be removed and then replaced with some insulating material under it (between concrete step and threshold). OR just replaced altogether with a less heat conductive material?

It is quite damp in our subfloor throughout the house - no standing water, just that it is slightly damp bare clay soil. We have spent most of 2014 digging out rubble and general carp throughout the ground floor and installing more air bricks to help.

There is a lot of cabling, pipes and all sorts in that part of the floor. The copper pipes certainly look to be damp from condensation - but i haven't found an overt water leak. I am in the process of lagging all the copper to try and minimise damp from condensation on the pipes.

 

[drpepe]

Can't see anything you can do, cold bridging is eliminated by insulation, where do you expect to put insulation?

You can try to ventilate locally around the area, but short of drilling holes or removing draught seals (probably a bad idea), I can't see how that will work.

Buy a non crappy aluminium door, sorry?

Thats a Composite door with part M compliant low aluminum threshold.


I have fitted about 100 of these doors and yes you can get a bit of condensation on the Ali parts but I dont think that will be causing your problems.

Is it as wet as it looks in that hole?
I would be checking the pipes for leaks, Making sure its ventilated under there. Make sure the steps are sealed on the outside.

Following some of the recommendations I have been given here I have decided to:

1) Seal the step on the outside (although rain doesn't really correlate with the 'condensation' inside - it seems to just be any cold weather - Nov to March basically).

In an effort to reduce direct contact between cold materials and humid air:
2) Paint the interior of the concrete doorstep with 'anti-condensation paint', above and below the floor level.
3) Fix a piece of timber ( quadrant or similar) to the interior of the concrete doorstep where it is exposed above floor level.

4) Also is there such a thing as a non-metallic low profile threshold? ie. to prevent thermal bridging as described above.

 

[drpepe]

View media item 90330
As you can see I may have found the cause of the cold bridging - a bleeding great gap under the threshold strip! (The concrete doorstep is now painted white). Presumably the cold air coming under will be hugely contributing to cooling the strip and causing the condensation?

Any idea what I could do about this?

Would silicon be sufficiently insulating to use here?