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Hello everyone,
I am looking for some recommendations or ideas on how to replace an external laundry door threshold/sill.
I attached few photos. As you can see on the photos, it is completely damaged and rotten.
Because it is an external door, it is always exposed to rain. When it gets wet, it expands which makes it difficult to open or close the door.
I am looking for some solution that would be weather resistant.
What type of timber would you recommend to use? Does it need to be treated to make waterproof and what product to use? What paint would you recommend?
I am afraid that using timber, I will end up in a similar situation several years later and it will rot again.
So, I am wondering if there are some other products I can use instead of timber, for example, stone, tiles, metal, etc.
Hi @alex27,
Thank you for your question about replacing a timber sill at your home.
Looking at your image, the timber used on your threshold doesn't look up to the task. Sills need to be sloped so the water will run off and away from the house. Yours appears to be installed level, meaning water will not run off as it should. This, combined with the knots in the timber will allow water to seep into the timber, causing swelling and rot over time.
Timber is fine for use in this application, but the right kind of timber is essential to prevent this swelling and rot. Use hardwoods like Merbau or Blackbutt, as these are more resistant to rot and weather exposure. Protect the timber with oil, varnish or durable exterior paint.
There are timber profiles, such as a French sill, that are often made using hardwood and are designed for this specific purpose with the slope cut into the timber. See the below image as an example.
As timber suppliers are often regional, I'd suggest speaking to the team at your local store's Special Orders or Trade Desk about the options available in your area.
As an alternative, composite materials, aluminium thresholds, or stone and tile options are excellent choices as they are highly resistant to rot and moisture.
For added protection, you might consider installing an awning above the door to stop some of the rain.
Allow me to tag @Nailbag and @Dave-1 to see if they have any advice they can add.
Let me know if you have further questions.
Jacob
Hi @alex27
The timber on your sill looks like treated pine thats been incorrectly utilised as a sill. As @JacobZ mentioned it isn't profiled correctly with no fall towards the outside, which has added to its deterioration. It's also much deeper than standard hence why you're unable to find a matching replacement size. It's normal for the brick/concrete along the front edge to be exposed past the depth of the sill. Have a look at some sills on friends or neighbours homes to get a better understanding. I've included below some images though not French sill, but may also help.
You will be able to easily source a suitable French Sill in Merbau as @JacobZ recommended. Though you can paint it, I would highly recommend using a good quality water based exterior like this one from Cabots, which will come up a treat and last a lot longer than a painted surface.
I have replaced quite a few sills over the years and it's not an easy task as it's installed before the door frame. Ideally you will need a multi-tool with a quality course wood blade and run it flush between the top of the old sill and each side of the frame. You can use a handsaw to cut vertically down at each end and then use a pry-bar to remove the centre section before removing the two small sections either side.
With regards to the Aluminium one, it may be integrated with the frame itself. So, we would need a photos or two to identify.
Nailbag
Hi @Nailbag,
Thank for your reply.
I think it would look a bit odd for the brick/concrete along the front edge to be exposed past the depth of the sill. If I install a 160 mm sill as @JacobZ recommended, I would have about 30-40 mm of brick/concrete exposed and it is hard to tell what condition it is in after I remove the old sill. Would it be Ok to cover the exposed area with some stone or tiles, or piece of hardwood board? Are there any recommendations?
Please advise the correct way of installing the new sill. Which one is correct, picture 1 or picture 2 ?
Hi @alex27 It's the first one mate.
Below is the profile how it would sit on the opening. The lip at the top of the sill helps to prevent water blowing up under the door, but not great. So I always install one of these automatic weather strips. They come in a few different colours to and take about 15-20min to fit.
Again it's normal to have the exposed brick/concrete past the sill. I'll try and get a better photo today of what it looks like. We will get a better idea once the old one is removed as to what it looks like exposed. But timber won't be the option or tiles. You could render the exposed area and paint it, which might come up to something you like and durable.
Nailbag
Good Morning @alex27
Feeling your pain, I have two sills at home that need to be replaced as they werent installed correctly. They have a fall on them but the first version wasnt enough and the weather strip that @Nailbag shows in the last post wasnt installed so my timber ended up looking yours. Once I installed teh weather strip the issue went away by 96%
Is the sill rotted? Or is it just waterlogged atm? If you can push a screwdriver into the timber then its rotted and needs to be replaced. If its solid then short term the weather stip and then keep on sourcing a wider sill to cover your door might be an option.
When I go to replace my sill I will be removing the vertical sides by leavering them gently off, in effect dismantling the inside of the door way so I can get to the sill. Will be doing that sometime soon so shall see if my theory holds up 
(I have a mate who has made up some replacement door sills so I am lucky I dont need to source them)
Dave
