Building a wood mezzanine in a cottage - advice & structural calcs?

[gaz1]

now i am going to throw in another one

a quarter build a single bed with a walkway down one side size reference 7ft-8ft wide length 14ft

now you can build this by lowering the floor so you have headroom at the roof at 3ft wide standing area at side of the bed

this also means you get to store under it

yours would be 7ft-8ft wide x 4m length plenty to play with at that

 

[KaneH]

Hi Nomad, bit of a left field suggestion here but you could potentially form a timber Vierendeel truss spanning the 8m wall to wall. Based on your geometry, it appears as though you’ll have ~1200mm height for the truss below the rafter line which would be doable. Would involve spliced connections in the timber so likely nail plates which can be a tad unsightly.

Failing that, and to avoid an intermediate post, could you install intermediate timber beams spanning front to back (your 4.5m length quoted)? Based on your 2270mm head height, you would likely have to half lap these to the ends of the rafters as they’d be ever so slightly higher than the existing wall plate on the 2.2m wall. Close enough to the support that you’re unlikely to cause an issue with the rafter (worth checking the increase shear on the timber however).

The new edge timber forming your storage deck could then span from wall to intermediate timber then into the other existing wall. Pop two intermediate timbers in and your edge timber would only need to span ~2.6m keeping the sizes down. Having two sections of structure passing through an 8m long room at the low eaves level is unlikely to be too intrusive either.

 

[addjunkie]

Hi, there. For an ongoing project of mine I'm looking at putting a wood mezzanine in the main room (partly as it's a tiny house with no storage, also for the possibility of putting a mattress up there as it's a good level to look out of the velux window and views will be rather special).

Ideas & suggestions welcome, especially dimensions for the main support beams.

The room & planned floor :
View attachment 485885

An idea of what I'm hoping for:
View attachment 485886
View attachment 485887

Requirements:
Length approx 8M / 24ft (I'll measure and confirm)
Spacing for beams 130cm (there's a gap on one wall that the beams will fit into, I can't alter this)
Width for flooring - maybe 140cm so I can put a double mattress up there?
Weight? Optimistically a lightweight bed + 1 large / 2 medium people at one end, bulky storage ( maybe some heavy tools??) at the other.
Minimum would be 1 person up there moving light bulky thing into storage.
No vertical supports to floor level (space is tight on the ground and having vertical beams supporting this will be a problem)
Weight limit?

For the future :
railings / fence to stop people & things falling off ! (legal railings are stage 3 and not needed yet, fitting the framework is stage 1, fitting the flooring is stage 2)
steps (I'm thinking a lightweight stepladder I can move onto position when needed)
Head height above will be limited but fine for storage or sitting up on a low bed.

I can do the building work myself but don't know what size support beams I need (I'm expecting to put a lintel into the end walls and rest the beams on that)
Tell me your thoughts

The room is 4.5m back to front, your front wall only 2.2 high …..

How about turning your mezzanine by 90 degrees. 4.8m timbers are readily available. Support the timber at-the front wall only a small pillar taking up very little room space. Your 2.27 (7ft3) ceiling height though low is adequate, especially if its properly lit with down lighters. If your worried about fixing the ledger and the beam unto the walls, use a small pillar to support just fixed to the wall, weight down to the floor. Or use steel joist hangers, personally Id a joist hangers into the back wall.

https://www.screwfix.com/p/simpson-strong-tie-masonry-joist-hangers-47mm-x-215mm-4-pack/202tj

I used similar in the storage barn to build a mezzanine, its 4.7 wide 8x2 timbers and it didnt bounce too much, when floored. Two people up there no problem when the solar inverter was carried up and fitted.

The barn I posted earlier down stairs has a low ceiling of 7’3, and isnt an issue. Apart from the plaster board not being quite level, before anyone comments.

 

[DAPPH]

Thanks everyone, answers in no particular order :
The left wall and the left 2/3 of the back wall are "old farmhouse" build (at least a foot thick, concrete both sides, infill a mix of rubble, cement, clay..), the right wall and right 1/3 of the back wall are new brickwork.
Good point about sourcing 24ft lengths of timber - I need to look at options, getting it on-site and into the room will be do-able with a helper.
Metal is my least preferred option for this (apologies - I know it's a welding forum ! )
The roof is quite new and was over-spec'd to allow for solar panels etc in the future, I had already thought about suspending some of the mez weight from the roof. It's an option and there are 10 roof beams so plenty of loadsharing.
A flitch beam (timbers & steel plate sandwich) is something i hadn't thought about, good idea.
I have furniture on the left wall that is 227cm high. Ideally the base of the new floor (ie top of the new beams) will be a fraction higher than this, this leaves head height of almost a meter above the front of the new mez, about 1.8m at the back. It's not ideal but at present it's wasted space in a house that has almost no floor space. Beams would be lower than this but it's an area where you don't walk around so some loss of head height is ok.

Keep the ideas coming, it's all appreciated

Storage racking uprights use four or six as full length runs bolted or welded in situ , clad the things in a decent wood that when stained matches the other wood in the place
They come in 6 mtr length and can have staggered internal connectors slipped inside \\7 bolted up or welded to make the length ensuring there is at least a metre separation between any of the joiners There is plenty of hole to screw wood / cheeks sleeves to
A few weeks ago they were priced at £87 each , check with Fizzy ....he priced them for me .

Individually they are not that heavy .

 

[fizzy]

Just for ideas

Support beams can be made into a feature. Paint them, black and get a steampunk type effect which can look nice.
Or cover steel beams with wood.
Some designs look really good.

 

[Erie Fred]

This ^^^, weld up end fittings with holes for lag screws into timbers, make truss rods as well, painted black for effect.

 

[Nomad]

Updates, photos & an embarrassing confession

First the photos after I mocked up a CAD (cardboard) shelf.

View to the right: the blue upright is in line with the doorpost, 82cm from the right wall and leaves space for an 80cm wide unit. It’s slightly in the way…


View to the left. The yellow upright is next to the sofa, 1.1m from the left wall. It’s slightly in the way but still leaves space to use the kitchen bench & the wardrobe on the end wall.


Confession time - measuring things the room is 5.7m wide ( not sure why I was sure it was 8m).
Supports where the blue & yellow uprights are leave a central span of approx 4m. I’d rather not have vertical supports but if it’s an easy solution I’ll consider it.

For background, the gap between the kitchen & back wall is 1.3m deep which dictates the spacing between the beams / max width of the shelf.


I’m still deciding but a floating platform on 4 vertical supports is a definite possibility. Watch this space

 

[gaz1]

a post here would be better dont need them at the walls

 

[addjunkie]

I have calcs for 5.7m steel beam. But I think it could be done using off the shelf c24 8x2 timbers, put a mezzanine on the right hand sided wall, use small pillar at the front wall 3 6x2 timbers fixed together would support a pair or even 3 timbers across to the back wall. Joist hangers in the back wall. Bolt 2 or 3 joists together. Then use another 8x2 parallel to the back wall from the cross ways joists. Run another along the back wall and brace in between for a floor. Then use a space saver type stair in the back corner.

 

[Erie Fred]

Some pix to spark some ideas.....and to add steel & welding content.....

Gallery

woodboardsandbeams.com

 

[DAPPH]

Thinking through your support across the room

Back in my telecom days, I had to install two ISDN2 lines into a bungalow that was being modernised . The roof void was truly cavernous almost 12 feet from the ceilings to the apez.
The guy had a professional architect doing over watch on the job he told me the void was going to become a six person office . Thinking of some of the plans for my under refurbishment home (myself & my wife doing it ) I asked how he would lift the roof , build up walling and insert the joist for the floor .
" Oh we are not doing that , come here and see what we are doing " .

He had made a a dozen of more joists like Battenberg cakes the length of the extended bungalow using 6 mtr lengths of staggered jointed , five off 75 x 25mm OD x 2.,5 mm wall hollow box section steel tubes , used steel strapping to pull three on their 75mm sides tight together and tig welded the adjacent faces every 50 mm for about 20 mm this was then sandwiched between the other two sections which were also steel strapped before welding


It was done inside the roof void and as each individual tube was not too heavy they'd slid them in through nice round core drilled holes in the gable ends . Could you do a similar thing with 6 mtr hollow box tubes ?


Perhaps putting strong welded up steel " hayracks as a buttress support at the ends ( chemical anchored in using long anchors ) and turning them into a room feature as well

 

[gaz1]

there is another

pallet racking that takes alot of weight

 

[DAPPH]

there is another

pallet racking that takes alot of weight

Already mentioned it to Nomad , Gaz

 

[gaz1]

@Nomad

you might as well update this post