Lintel above doorway - moisture and insulation

11 Jul 2017
Reaction score
United Kingdom
My house has a pre-existing single-story extension on the side. A doorway has been knocked thru the previously external wall to give access from the kitchen to the extension. The house itself is timber frame with brick skin.

Above this doorway there is an L-shaped steel lintel in the brickwork, however the vertical face is on the extension side rather than within the cavity. It is my understanding that this is the wrong way around - am I right?

Also, the doorframe head is a couple of inches shy of the lintel, with nothing packed in the gap.

When the roofline lead on the extension failed, water ran down the brick face. When it got to the lintel, the lintel then guided this water into the cavity of the original house. It seems to me that the correct fix is to turn the lintel around so the vertical face is inside the cavity. Is there any other option? Could I fit a flashband across the face of the lintel, even temporarily?

Also, should the gap between the lintel and the doorframe be filled in some way? The extension is quite cold as we don't really use it, so I think a lot of heat escapes the house via this doorway.


Here is my attempt to draw a cross-section of the doorway, hopefully it clarifies.
Sponsored Links
Hopefully I'm ok to bump this as it's been a few days. Anyone got any knowledge they can share? Should this be in the building forum?
Have you got a photo of this doorway as it doesn’t look on the information supplied that it has been fitted correctly.
Thanks for the response. I've included a photo of the side of the frame with the reveal plasterboard removed. As you can see, the frame is fixed to the timber frame, and the old external brickwork now forms the internal wall of the extension.


This is as good as I can do on the head due to problems with the light. As you can hopefully see, there's an L-profile lintel supporting the brickwork and the frame head is flush to the house timber frame, but not attached to anything other than the legs of the frame. The random piece of wood under the lintel is something I screwed into the brickwork in advance of re-fitting the plasterboard, but I'm having second thoughts, hence this thread.

Last edited:
Sponsored Links
Ok Daggermark, first of all wish I was around the corner that would be easier. Building regs changed a number of years ago and forced window and door fitters to include flat iron as a reinforcement to existing lintels such as wood and brick or soldier structures. It appears your L shaped lintel is the wrong way round. The door has been measured wrong and should at least have had an addon which is a gap filler normally used to offset a hinged area for a door against the plaster line. In summary there’s not a lot wrong, have the door refitted. Have the lintel turned around. Fill existing void between frame and lintel with wood-or plastic then to help with the draughty doorway use febfoam or equivalent to seal around the gaps. As for the water ingress into your property that’s a simple lead upstand fix by replacing your lead flashing. Once again this could be something simple but would love to have a look just to be certain. Hope this helps. Kind regards John.
Thanks John, I think I understand most of that. I've fixed the lead fixed already, I just wasn't sure if there should be some additional insurance if it fails, to avoid the water coming thru the plasterboard on the frame head. I'll get that lintel turned around and use timber/foam to fill the gap as suggested.

The only bit I'm not sure about is what you mean here:

The door has been measured wrong and should at least have had an addon which is a gap filler normally used to offset a hinged area for a door against the plaster line.

I can't quite picture this. Do you mean the frame should be full-depth with a smaller reveal?
Yep, you’ve got it. The frame should fill to the lintel but if the internal and external plaster lines are different then you fit to the smaller fix and infill the difference. Kind regards John.
Nice one thanks!

Edit: Should there be a cavity closer fitted in this situation?
Last edited:

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.

Are you a trade or supplier? You can create your listing free at DIYnot Local

Sponsored Links