Door threshold in MBC timber frame

[Jeremy Harris]

TBH, I was a bit uncertain of what to do with our slab, as I hadn't thought about it until the day before the concrete pour, when the MBC lads asked me what to do at the door thresholds! 

 

There followed a bit of mild panic while I thought about their suggestion to cut a 100mm x 100mm section from the wing insulation at every door, and concluded that the effect was pretty small, given that the frame of the doors was a bigger thermal bridge.  For us it worked perfectly, the door frames fitted so their outer faces were flush with the frame outer skin and the extended cills projected out about 70mm, enough to overhang the cladding base strip (which is 18mm black uPVC) by a bit over 25mm.

[jack]

We have exactly the same detail, which was suggested by our architect and tweaked a bit by our window supplier.

Do note that the recess and step formed in the slab isn't as precise as the rest of the MBC's work, as as it's formed onsite by offcuts of wood and foam before the concrete pour.  I'd suggest forming it slightly deeper than needed, and making up to final level with something like a reinforced screed product.  Ours ended up being a lot deeper than needed so we used reinforced self leveling screed to get within 25mm of final depth, then made that up with a layer of exterior grade plywood.  

 

Personally the plywood aspect of this worries me a bit from a long term perspective.  I now wished we'd been able to get the depth right just with the reinforced screed.

[dogman]

My biggest issue is that the 3 large lift and slide windows have to be fully supported. My only option is to set the frames back into the frame and get the longest cill i can from Munster.

My wife's choice of floor (stone) means that to ensure the frames are flush with the floor i will only need to recess about 18mm so easy to achieve with some ply.

The front and side doors due to the part M thresholds will need to be lifted slightly anyway  

Munster come to site to measure so hopefully any errors can be avoided.

I was hoping to start on the 6th March but i still have not had the finished plans from them so will now have to push it back again( the first delay was mine)

[Oz07]

Yes I would of thought 100mm just where the doors are is no major. With regards to cutting a channel into eps is this done with hand saw. Also where is the shuttering added and what does it achieve in @TerryE solution? Any sketches?

 

edit. Think I understand the shuttering lowers the frame Cill below ffl to help with part m

Edited February 20, 2017 by Oz07

[Jeremy Harris]

The Munster doors don't need lowering, they are fine WRG to Part M just fitted at slab level, as long as the floor covering is at least 10mm, IIRC. We used 12mm bamboo or travertine and this ended up pretty much level with the low-profile Munster thresholds.  I'd rather the thresholds were higher, TBH, as there's only a few mm of clearance under the doors when they open and no room for a doormat (I'm going to have to cut holes in the flooring and fit recessed mats, I think).

[dogman]

As @JSHarris has mentioned i will most likely lift the front door and side door as they have part M thresholds and are 35mm high. They specify 15mm clearance with 20mm floor

The sliders are 55mm and i am lowering them 18mm so with a 20mm floor covering i have a 17mm trip hazard . As i can fall over a leaf this should prevent embarrassing moments

[Barney12]

14 hours ago, dogman said:

I was hoping to start on the 6th March but i still have not had the finished plans from them so will now have to push it back again( the first delay was mine)

 

You are not alone there with MBC. My groundworker is booked for the first week of March and I've yet to see a single drawing or design detail. However, I have promises that I'll have the information in time and communication is good.

[TerryE]

15 minutes ago, Barney12 said:

 

My groundworker is booked for the first week of March and I've yet to see a single drawing or design detail.

 

They use a rolling allocation: the team moves straight on from one job to the next.  Our date ended slipping by 2 weeks.

[Barney12]

1 hour ago, TerryE said:

 

They use a rolling allocation: the team moves straight on from one job to the next.  Our date ended slipping by 2 weeks.

 

I'm not panicking (yet ) its taken 4 years to get to this stage so all progress is good progress!

[Jeremy Harris]

If it's any consolation, I know that I held up our build for around 6 weeks, because of the drilling rig fiasco during our ground works, and that must have had a knock on effect to those in the chain ahead of and after us.  I bet we're not the only ones to have held them up, either, so they have to be pretty good at changing plans on the fly and delays may well be out of their hands (as in our case).

[Barney12]

Just now, JSHarris said:

If it's any consolation, I know that I held up our build for around 6 weeks, because of the drilling rig fiasco during our ground works, and that must have had a knock on effect to those in the chain ahead of and after us.  I bet we're not the only ones to have held them up, either, so they have to be pretty good at changing plans on the fly and delays may well be out of their hands (as in our case).

 

My biggest concern is availability of follow on trades. In particular I have an electrician and plasterer (not the same person!) that I know and trust. They are good and thus are booking way into 2017.

 

[TerryE]

@Barney12, one of the hardest lessons that Jan and I had to learn is to accept that a build is going to take a lot longer than we initially planned.  As a single self-builder you will have very little clout in making sure that trades will arrive on the date initially promised, and then when they do, it's a case of sods law and some other tradesman that you needed to complete before they could start is running late.

 

The more that you crash the build timescales, the more stress you are going to have; the more its going to cost you; and the more compromises that you are going to have to make.  Not good.

 

You and your partner just need to ask yourself what the true cost financially and on your life is a 6 month slip going to make.  An honest assessment.  If the answer is that you aren't going to die in a ditch then I would suggest that you stretch the timescales.  Add time contingency between the the key build phases.  Then you are continually stressed to hell and having to reschedule trades.

 

There are a lot of upsides to taking your time as well. In our case, there was a long lag whilst we got all of the planing and preconditions through the approval bureaucracy, then a flurry of activity in Oct / Nov 2015 when the slab, frame and windows went in.  We didn't do boarding out and plastering until a year later, but in that time we could experience the space and in doing so we realised that we'd got things wrong, so we could shift a few internal walls, add another wetroom; shuffle upstairs room allocations.  We also allowed the whole frame to stabilise  and the slab to totally dry before the external stone skin went up and we laid the ground floor and boarded and plastered. Three months later we haven't got a single drying/settlement crack.

 

Doing a self build is stressful enough as it is.  Don't pile rocks on your back.

[Jeremy Harris]

26 minutes ago, Barney12 said:

 

My biggest concern is availability of follow on trades. In particular I have an electrician and plasterer (not the same person!) that I know and trust. They are good and thus are booking way into 2017.

 

 

That is a challenge to work around! 

 

I was lucky, because I'd left plenty of time for me to do a lot of first fix work, like the plumbing, ventilation and heating systems, putting a lot of the hardware in place for the electrical first fix etc, so the only real problem I had was delaying the roofers, who were a fairly big company and able to reschedule.  The scaffolders seem to be used to changing things at very short notice, so weren't a problem at all.

 

I ended up doing some things out of the order I'd planned, because of the delay and the fairly fixed schedule the electrician had, but that just meant me moving some of my first fix work to after the electrician had finished his bit.  As we had Christmas in the middle of this phase, we had a couple of weeks where no one was available anyway, during which I could do some of the catch-up work before the plasterers arrived to start boarding the house out.  Even then I was right up against it, as I was still running network cable around and fitting acoustic insulation whilst the plasterers were boarding out - it was a bit of a race at times for me to get things in before they were ready to board that area out!

Edited February 21, 2017 by JSHarris

[Ferdinand]

Returning to topic :-), have we got a good and practical solution for these door thresholds? This has been niggling at me.

 

The option of adding a concrete tongue to the slab by cutting out a slice of insulation seems OK and, as has been said, reducing 200mm of insulation to 100mm is not exactly a huge sacrifice even in the context of a very low energy house.

 

However, are there low conductivity materials which can be inserted as a threshold instead of using a concrete tongue to slab level? One detail would be to make the concrete tongue below the level of the slab to create space to insert a (more) insulating material, which also needs to be sufficiently strong in compression and have a lifetime of perhaps 40-50 years.

 

What could that material be?

 

One option would be Terry's Porotherm blocks, or maybe something with Leca as the aggregate (Leca-crete blocks)?

 

Others that come to mind are the driveway pavers that are made from 90-95% recycled rubber products, or a composite plank (thinking of something like the plastic decking planks but more structural), or even wood (an oak threshold - we use oak as soleplates?).

 

Am I barking up the wrong tree here?

 

Ferdinand

 

Edited February 22, 2017 by Ferdinand

[Jeremy Harris]

1 hour ago, Ferdinand said:

Returning to topic :-), have we got a good and practical solution for these door thresholds? This has been niggling at me.

 

The option of adding a concrete tongue to the slab by cutting out a slice of insulation seems OK and, as has been said, reducing 200mm of insulation to 100mm is not exactly a huge sacrifice even in the context of a very low energy house.

 

However, are there low conductivity materials which can be inserted as a threshold instead of using a concrete tongue to slab level? One detail would be to make the concrete tongue below the level of the slab to create space to insert a (more) insulating material, which also needs to be sufficiently strong in compression and have a lifetime of perhaps 40-50 years.

 

What could that material be?

 

One option would be Terry's Porotherm blocks, or maybe something with Leca as the aggregate (Leca-crete blocks)?

 

Others that come to mind are the driveway pavers that are made from 90-95% recycled rubber products, or a composite plank (thinking of something like the plastic decking planks but more structural), or even wood (an oak threshold - we use oak as soleplates?).

 

Am I barking up the wrong tree here?

 

Ferdinand

 

 

The key thing is that this threshold support has to be integral with the slab, so that there is no chance at all of differential movement.  The cut-out in the upstand method is very simple and ensures that the slab and door threshold are contiguous.  There's very little room to secure any other material to the slab, so that it would never move, as we're talking about a strip 100mm x 100mm x the door width, that would need to be secured to the slab somehow.  Remember the DPM is under this, so there really isn't a simpler way to detail this that I can think of.

[TerryE]

7 hours ago, JSHarris said:

The key thing is that this threshold support has to be integral with the slab, so that there is no chance at all of differential movement.  The cut-out in the upstand method is very simple and ensures that the slab and door threshold are contiguous. 

 

This and you should have rebar reinforcing through the tongue back into the ringbeam.  As J says, the cut-out method allows the tongue to be formed in the same pour as the slab itself. 

 

Yes you will get some degree of bridging because of reducing the EPS upstand at the doorsaw, but it you do the heat flow calcs, this is only a small number of W so long as you maintain some insulation thermal break.  We used FoamGlas because I had some left over but it could even have been 25mm EPS.  (We slated over ours.)    The critical issue is not the absolute W, but that you don't want any surfaces in the door reveal getting below the dew point for the room and therefore getting condensation.

 

[jack]

If you're really worried, you could add back a slice of 100mm of EPS to make up what you've lost, and cover it with whatever step, deck or whatever you're planning for the external transition from the door.

[dogman]

I intend to add insulation to outside if i can. 

this is the design i have been sent

 

slab.pdf

[TerryE]

6 hours ago, dogman said:

this is the design i have been sent

 

Just remember that you need to protect the external vertical face of the EPS with a rodent-proof barrier.  The last thing that you want is Rattus Norvegicus or even Tommy Titmouse setting up home in your EPS and starting a family there.  We chose a perimeter slab path and an engineering brick plinth because this was zero maintenance for the life of the house, but others have used steel mesh and render.

[dogman]

steel mesh and render for mine

However a think the way @TerryE has finished the detail is really elegant solution and i wish i had seen it a lot earlier 

i do have a plinth around half the build so its only one end that is to be rendered

Edited February 22, 2017 by dogman
.

[Russell griffiths]

Having just read this lot I wonder if @TerryE has a pic of how he finished his upstand to his eps. 

Many thanks. 

[HerbJ]

I have been thinking about this  since I completed my house, in a similar way to @JSHarris and @jack above (in fact using a variation of his detail for my sliding windows), as I always felt that I could/should have done something better..... 

 

Anyway, I still get regularly emails/newsletters from Greenbuilding Store and in a recent  Newsletter they detailed an improvement that they have made to  detailing of door threshold to reduce cold bridging using a product called Compacfoam - https://www.greenbuildingstore.co.uk/products/compacfoam-200/. 

 

This product may offer a good solution to cold bridging for various different construction methods, including the passive slab and I can see how I could have improved my detail for door threshold.  I have no idea of cost, but Greenbuilding Store would appear to be stockists.

Edited May 29, 2018 by HerbJ

[Bitpipe]

On 22/02/2017 at 22:24, dogman said:

steel mesh and render for mine

However a think the way @TerryE has finished the detail is really elegant solution and i wish i had seen it a lot earlier 

i do have a plinth around half the build so its only one end that is to be rendered

 

I'm applying a 200mm band of Ubiflex, the lead flashing replacement on the strip of exposed EPS - its a mesh bitumen sandwich finished with stone chips so looks quite smart.

 

8 minutes ago, HerbJ said:

I have been thinking about this  since I completed my house, in a similar way to @JSHarris and @jack above (in fact using a variation of his detail for my sliding windows), as I always felt that I could/should have done something better..... 

 

Anyway, I still get regularly emails/newsletters from Greenbuilding Store and in a recent  Newsletter they detailed an improvemnt that they have made to  detailing of door threshold to reduce cold bridging using a product called Compacfoam - https://www.greenbuildingstore.co.uk/products/compacfoam-200/. 

 

This product may offer a good solution to cold bridging for various different construction methods, including the passive slab and I can see how I could have improved my detail for door threshold.  I have no idea of cost, but Greenbuilding Store would appear to be stockists.

 

I'm sure a strip of EPS 300 or equivalent would have the same load bearing properties - we used EPS 200 in our basement slab and it was rock hard - did not need to cut any thank goodness. However challenge would be getting the foam cut to size (I could only get it in 1200 x 2400 blocks.

 

For our thresholds we cast the walls as flat and then when applying the external 200mm thick EPS 70, first resin bonded 200mm cuts of rebar 100mm into the wall at regular intervals and then tied a bar across that. The EPS had a 100mm x 100mm x window / door length channel cut in the top and that created the former for the concrete that formed the corbel.

 

So each one still has 100m insulation vs 200mm elsewhere. Corbels still needed about 75mm timber buildup to enable the doors to be flush with internal floors - could have tried to do that in concrete but wanted to wait until  frame was up and sub floor in. 

 

[TerryE]

4 hours ago, Russell griffiths said:

Having just read this lot I wonder if @TerryE has a pic of how he finished his upstand to his eps. 

Many thanks. 

 

Russell if you look at the first of the pics in my blog entry, then you can see how the concrete spanned the eps and I also put some wood shuttering n the outside (and rebar reinforcing inside wired to ringbeam box rebar) so that the concrete tongue spanned the ring EPS and closed the 50mm airgap to the out stone skin.  We had slate throughout the ground floor and I also used the same as the external steps.  Beneath this I used a line of foamglass butting up to the tongue to break the bridge.    The test was the really cold spells in winter.  The inside floor next to the doors was maybe a few degrees colder than the ~22-23°C elsewhere but not noticeably so and well above condensation temperatures.   

[Tom's Barn]

On 16/08/2016 at 16:16, Alex C said:

I have just been through this and have flush internorm lift and slide as well as front and back door. Internorm will want you to support as much of the aluminium extrusion at the base as possible (well actually all of it). I have attached my sections that everyone eventually seemed pretty happy with. The issue is actually managing to shutter the slab accurately on site to get a level step down detail. My installers from Ecohause were not only expensive, but also terrible, but after several attempts managed what seems to be ok. When you say approved detail, who do you want it approved by? No-one is going to sign on a dotted line with anything other than full support to the slider or door base, but obviously that will be a massive thermal bridge.

 

 

window gf06 section.pdf

sliding door section.pdf

Hi Alex

 

any chance you can report your sliding door section. I am just working through my window requirements and how I make the cill detail work. Being able to see others would be a great help.

 

Many thanks in advance

 

Tom