Shorter Internal Doors

[Ferdinand]

I may have been a little enthusiastic with my floating floor insulation for the Little Brown Bungalow, and I now need some shorter than normal doors. A classic oversight.

 

The arithmetic is that I have specified 50mm Celotex between 36.63mm battens on their side, them 18mm OSB, then underlay and a floor covering (laminate, engineered wood, vinyl or carpet depending). That equals a need to cut off approx 63+18+10 = 90-95mm, plus any air circulation gap I decide I need. There are 6 doors.

 

The plan had been to go with Geneva or perhaps Shaker style oak veneer doors from someone like Todd Doors, where they can be bought for £60-80 inc. VAT.

 

Existing doors are standard imperial 1981mm height.

 

So without butchering the doorframes, and I do not plan to go there, that means I need doors which can be trimmed by almost 4 inches, or find a supplier of shorter or custom doors, or reduce the floor depth. Options seem to be:

 

1 - Bespoke eg pine doors. These seem to start at £150-£200, so are probably a non-starter.

 

2 - Find some doors at OK prices which can be trimmed to about 1890mm, or by 90mm. The best I have seen so far are the Todd Doors' doors which can typically be trimmed by 50mm base and 12mm top = 62mm total.

 

3 - Use slab plywood doors trimmed as needed and recapped. The bungalow had slab doors before, but I was planning on a more upmarket feel.

 

4 - Reduce floor thickness - could be done by using 36x63mm battens on their face not their edge and 25mm Celotex not 50mm. That would give me an additional floor depth of 36 + 18 + (8 to 10) which can just squeak under the 62mm cutting limit of the Todd Doors.  I would need to store or sell the pallet of 50mm Celotex sheets I have already purchased, and buy 25mm. I will have a use for the other within a few months.

 

Any comments - particularly for trimmable doors - would be welcome.

 

I need to decide this over the weekend at the latest.

 

Ferdinand

 

 

[jack]

Can't solid-core doors be trimmed by that much?  The bottom edge would likely then be end grain, but is that the end of the world in that position (genuine question)?  I suppose the risk is cupping or distortion due to the lack of end piece.

 

We bought plain (primed) solid fire doors locally from somewhere like Benchmarx (or maybe one of the big builders' merchants) and I was amazed at how cheap they were.  

[Mr Punter]

Why the battens?

[Ferdinand]

WHile I am on doors, Todd Doors have some 4 panel oak veneer doors with the complex mouldings reduced from £224 to £50 in their sale.

https://www.todd-doors.co.uk/4-panel-oak-door

 

Not suitable for my property unfortunately, but perhaps an option for some people.

 

6 minutes ago, Mr Punter said:

Why the battens?

 

That is my normal way of doing insulated floating floors to make sure it will last no matter what.

 

Ferdinand

 

Edited May 12, 2017 by Ferdinand

[ProDave]

Suggest the battens on their side with reduced insulation. space them 400mm apart and then you can use 18mm chipboard as the final floor straight onto the battens, then carpet.Total thickness 54mm plus carpet plus air gap.

 

If fitting a wooden floor, find an engineered floor that can span 400mm and fit that direct to the battens. forget any OSB underlay sheet.

[Stones]

Speaking from the point of view of a taller individual, reducing the height of a door by the amount you suggest would make me walk away from the property as a potential rental.  Is there any scope to raise the door frame header so you can still accommodate a standard door?

[Simplysimon]

90mm reduction equates to the removal of the top rail, that's a lot.

38 minutes ago, Stones said:

Speaking from the point of view of a taller individual, reducing the height of a door by the amount you suggest would make me walk away from the property as a potential rental.  Is there any scope to raise the door frame header so you can still accommodate a standard door?

 

+1 on the above, move the linings, it's the only sensible/logical option

[Ferdinand]

Thanks for the comments all. Now need to think over the weekend.

 

@Simplysimon @Stones The point about height is well-taken - though I am only 5'11". However they have concrete lintels, whcih is not a ballgame I wish to enter.

 

Following option 4 I can reduce my loss of doorway height to 55mm plus floor covering.

 

If I switch from 36x63 cls to 25x50 pse I can knock another 13mm off, which reduces the doorway height loss to 43-44 mm plus floor covering, leaving me 1.925m to 1.93m as the opening height rather than my suggested 1.890m above.

 

@ProDave thanks for the flooring comments.

 

There's a suitable compromise here somewhere, just need to find it.

 

Part of the answer may be a door design which makes it feel taller eg a vertical design emphases.

Time to go and spend half an hour standing in doorways on blocks of wood, and examining doorframes in detail, I think.

 

Ferdinand

Edited May 13, 2017 by Ferdinand

[bassanclan]

why not completely get rid of the 50mm celotex altogether?

[Nickfromwales]

Why not bond 30mm eps straight down and do away with the battens? The compromise in insulation will be helped a little by the lack of cold bridging through the battens. Just lay a floating floor, such as engineered laminate, and you've got a build up of less than 50mm. Doesn't help for the carpet / vinyl'd areas though as that would need a min of 18mm t&g deck regardless. 

Next question is though, why not insulate under the floor and ditch this huge ball ache altogether? Does the property have floorboards over joists, or do you have a mix / all concrete or screeded floors? 

[Ferdinand]

Decision not quite yet made on this.

 

I am going for 25mm celotex plus 18mm OSB, using 25x50mm roofing laths flat as battens.

 

That will give me a build up of 43-45mm plus floor covering.

 

I'll post my further reflections later on.

 

Thanks for for all the comments.

 

PS Forgot to mention that the above OSB would be moisture resistant OSB3.

 

F

Edited May 13, 2017 by Ferdinand
Oh me of little faith!

[ProDave]

I will be interested in your reasoning.

 

The 18mm OSB seems pointless. It's no good as a final floor for carpet, use 18mm chipboard floor panels for that, and it's pointless for a wooden floor as you can just use a structural floor straight onto the battens instead to minimise build up thickness.

[Simplysimon]

the solid insulation is fine as a support for the floor on it's own without the need for timber battens. i would also suggest using the chipboard flooring as opposed to osb. whichever board is used the pressure is spread over a sufficient area without damage to insulation and providing a better overall insulation solution

[Nickfromwales]

Best to add that T&G osb is also available so actually could be used for deck material. . 

I'd not use bare sheet of any type as the joints absolutely must be T&G'd for uniform support under foot / point load. 

 

Edit to add : P5 is moisture resistant and usually cheaper. OSB3 is overkill imo. 

[Onoff]

I'd use 22mm P5 all day long over OSB for a floor.

[Ferdinand]

On 13/05/2017 at 08:12, bassanclan said:

why not completely get rid of the 50mm celotex altogether?

 

@bassanclan

Thanks for the comment.

 

1 - I do not think that the 100mm rockwool (already in stock) I have put under the suspended floor between the joists will be enough (for me) on its own. That with just floor above will only be about 0.25 as a u-value.

2 - Services (electric, ch pipes) are running in a void in the floating floor.

 

On 13/05/2017 at 08:24, Nickfromwales said:

Why not bond 30mm eps straight down and do away with the battens?

 

On 13/05/2017 at 13:09, Simplysimon said:

 

the solid insulation is fine as a support for the floor on it's own without the need for timber battens.

 

 

@Nickfromwales @Simplysimon

 

Thanks for the comments.

 

I have never been entirely convinced by this. There seems to be a recommendation that heavily trafficked areas are battened - eg doorways plus corridors. In a rental I have no control over eg someone bringing in a Welsh Dresser or huge bookcases (as I have done).

 

And it seems easier to batten from the start.

 

One last question, though:

 

If I went for the fully floating option, how do I put a (say) 300mm wide service void round the edge of a room? Can I just make the guys run their services 50mm from the insulation in the rest of the floor and rely on it never moving, or do I need to batten the edge of the void for protection, and use a cork strip to absorb any expansion of the insulation sheets? Plus clearly a batten round the edge to support the floating floor.

 

Cheers

 

Ferdinand

 

[bassanclan]

I thought that the property was to rent out and eventually sell?

The return on the 50mm celotex will surely not be worthwhile. You've gone far beyond what people would normally expect with the 100mm rockwool and might even devalue the property with the shorter doors.

 

could the 50mm celotex not go under the floorboards too?

[Ferdinand]

Replying to this.

 

1 - I went with roofing laths as my support battens, and 25mm Celotex, with 18mm OSB3 over. Carefully sanded the OSB joints to reduce risk of imprinting, and I will chose my underlay carefully.

2 - The the service voids worked very well indeed, and also let me run cable ducts for future Sky etc.

3 - I reckon it saved a few hundred on the rewire / replumb by ease of access.

4 - Next time I will use a 30mm void as a slight bit of extra room would really help.

 

Doors are being hung next week.

 

Ferdinand