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MVHR retrofit - mounting unit above stairs


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I've purchased an MVHR unit and am planning installation. The best place from a space point of view is above the stairs in the stairwell. I've been examining the structure around the stairwell and wanted to see if I'm crazy and what I should watch out for? The last thing I want is this coming down on someone's head! 

 

Upstairs there are bedrooms to the left and right, an ensuite directly ahead. The ground floor has a block wall to the left and right of the stairs with studs and plasterboard inside these. There is a timber surround at 1st floor level around the stairs opening when I look up from beneath the stairs to either side. That's what I'm hoping to tie into. 

 

My plan is to use two pieces of plywood to the left and right and heavily tie them into into the wooden stairs surround at their base and further pin to the wall studs higher up. The plywood at the rear will be joined to the side plywood pieces with angle brackets and possibly also lightly pinned to the studs in the wall behind. I'll double up on the plywood where the angle brackets and MVHR mount goes and possibly reinforce the bottom of the side plywood pieces with some additional steel brackets there .

 

So the two side pieces hold up the rear piece which then supports the MVHR unit. The MVHR is mounted by means of a single horizontal steel V with two mounting holes, one at either end. The top rear of the MVHR hooks into this and two rubber standoffs are located further down the back to keep the unit in a vertical plane . 

 

Once installed I plan to reinforce with heavy duty shelving brackets and a pair of wooden beams directly underneath the MVHR for extra security. 

 

I don't trust the stud walls that much and certainly not the one directly ahead as it's not resting on anything. The left and right walls are my best bet. I'm hoping the wooden stairwell surround will hold the weight or I'd have to try to tie into the block wall somehow which would be harder without making a mess. Getting strong enough screws in the right place and enough of them to stop the MVHR tearing itself off the wall behind or causing cracks everywhere is the goal. So, is this approach crazy or should I open up the walls to the left and right and tie some steel or something into the 1st floor inside the stud walls? 

Thanks for all advice offered! (No, I've no idea how to get an MVHR unit up to that height, am considering helium balloons currently......!!)

 

mvhr mounting.jpg

Edited by mike2016
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It does not need to be so complicated.

 

Locate the studs in the 2 side walls.  Attach 4 by 2 (100 bu 50mm) timber horizontally fixed securely to each stud.  Fit 4 by 2 joists spanning side to side attached to the  bearers on the wall with joist hangers.  Fix the joists at 400mm centres and floor with 18mm chipboard.  Make sure the front edge of this new floor is at least 2 metres above the stairs to preserve required headroom.

 

Fix further timbers and studding to form the front of this new cupboard.

 

Access to this cupboard can either be by cutting a hatch through to one of the bedrooms, or by having a door on the front and accessed from the stairs with a ladder.

 

Clad the structure in plasterboard.  It may look better to form a sloping ceiling under the cupboard matching the slope angle of the stairs.  That might form a handy void to route ducting etc.

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18 minutes ago, Conor said:

How are you going to safely inspect and change the filters every few months?!!

Ye 'ol Ladder - I've a very low pitch roof above and tiny utility beneath which presents other challenges! This is the best worst location without killing off half an upstairs wardrobe which is an excommunicable offense! 

13 minutes ago, ProDave said:

It does not need to be so complicated.

 

Locate the studs in the 2 side walls.  Attach 4 by 2 (100 bu 50mm) timber horizontally fixed securely to each stud.  Fit 4 by 2 joists spanning side to side attached to the  bearers on the wall with joist hangers.  Fix the joists at 400mm centres and floor with 18mm chipboard.  Make sure the front edge of this new floor is at least 2 metres above the stairs to preserve required headroom.

 

Fix further timbers and studding to form the front of this new cupboard.

 

Access to this cupboard can either be by cutting a hatch through to one of the bedrooms, or by having a door on the front and accessed from the stairs with a ladder.

 

Clad the structure in plasterboard.  It may look better to form a sloping ceiling under the cupboard matching the slope angle of the stairs.  That might form a handy void to route ducting etc.

Nice! So the MVHR would be floor mounted rather than rear mounted? 

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2 hours ago, mike2016 said:

Nice! So the MVHR would be floor mounted rather than rear mounted? 

Floor or wall, however it fits best bearing in mind you need access for filter cleaning / replacement so you need space to stand or kneel while servicing it.

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