Kitchen wall unit to D&D plasterboard fixings?
- Thread starter DonutHole
- Start date
Sponsored Links
Thanks kbdiy, I've not been very impressed by the strength of Thermalite in a drop test, but I just found a 1/4 piece of Thermalite, and tried some test screws. I drilled a 6mm pilot hole, used a red raw plug, and a 30mm PZ wood screw, Then a 7mm pilot, brown plug, and a 40mm screw the same result. Then a 5x75mm PZ wood screw with no pilot hole or plug, then a 5x100mm the same, and finally a 7.5x102mm concrete frame screw designed not to be used with plug but a 6.5-7mm pilot hole into brick.
For all of them I set my Bosch green 24v cordless to 2 (it only has a 1 to 5 scale) and they all went in tight, clicked on the ratchet (didn't spin) and seemed to give a good fixing, except the 7.5x102mm when I used No5 torque setting. The red plug I drilled on the corner about 1" from each edge, it broke out when I tightened the 30mm screw, and the 7.5x102mm exploded a small/medium piece off the back of the block. Off course I would loose 20mm for the D&D so probably would not happen in practice. The only trouble is knowing where the edge of the block is when you are drilling as if you are within a inch of the edge you are likely to explode it. Otherwise it wasn't any harder to drilling/screw than a piece of softwood. I was actually better than I'd though, if I get 4 good screw fixings per wall unit I think they should hold OK.
For all of them I set my Bosch green 24v cordless to 2 (it only has a 1 to 5 scale) and they all went in tight, clicked on the ratchet (didn't spin) and seemed to give a good fixing, except the 7.5x102mm when I used No5 torque setting. The red plug I drilled on the corner about 1" from each edge, it broke out when I tightened the 30mm screw, and the 7.5x102mm exploded a small/medium piece off the back of the block. Off course I would loose 20mm for the D&D so probably would not happen in practice. The only trouble is knowing where the edge of the block is when you are drilling as if you are within a inch of the edge you are likely to explode it. Otherwise it wasn't any harder to drilling/screw than a piece of softwood. I was actually better than I'd though, if I get 4 good screw fixings per wall unit I think they should hold OK.
Thermalite block requires twisted plugs ordinary plugs will just pull out.
One example
http://www.ebay.co.uk/itm/like/3505...f11=ICEP3.0.0&ff12=67&ff13=80&ff14=95&ff19=0.
One example
http://www.ebay.co.uk/itm/like/3505...f11=ICEP3.0.0&ff12=67&ff13=80&ff14=95&ff19=0.
Links in this post may contain affiliate links for which DIYnot may be compensated.
Sponsored Links
Links in this post may contain affiliate links for which DIYnot may be compensated.
You ignore the dot and dab they are screwed into the blockwork flush. A spacer is useful between wall and surface.[offcuts of pipe make good spacers either copper/aluminium or rigid plastic]
So confession time, it's for my new build kitchen and the wall hasn't been dobed & dabed yet I took my testing a stage further, and you can see my rig test, made from 1off 100mm Thermalite block, 2off 25x30cm shelf brackets, and some bathroom scales. I tested different fasteners that I happened to have to hold the shelf bracket to the block, 1 at a time, pushing on the bathroom scales and making a note of the maximum force they could withstand. I tested 7 different fastening arrangements, 3 times each and came up with the following results. Obviously if I had made to effort to dob and dab some plasterboard onto the front of the block it would have been a better test. My Green Bosch 24v only has 5 Torque setting, and Torque = Drill setting.
Wood Screw, Plug (mm), Torque, Kg
4x30mm, No Plug, 1, 15kg
5x40mm, No Plug, 1, 20kg
4x30mm, Yellow, 25mm, 1, 25kg
4x35mm, Red, 30mm, 1, 40kg
5x40mm, Brown, 35mm, 2, 70kg
5x100mm, No Plug, 2, 70kg
5x40mm, 14x33 Self Screw, 3, 70kg
(can you do table on here?)
At 70kg the shelf brackets started to bend, and I am only 77kgs so it was not possible to test beyond this. Also with 4 fixing per kitchen wall unit, 70kg x4 = 280kg, so not really necessary to test beyond this other than out of curiousity. Interestingly on a best of 3 the Self Screw aluminium plasterboard plug failed first at 10 then 20 and finally 70kg, so results not consistent. It shows that the correct size of pilot hole and torque used is very important, any cracks and it is severely compromised. I didn't test the 7x120mm screw with the 10x120mm Rawl Plug, frame fixing, because it would clearly hold more than 70kg.
Conclusion.
I don't want to use the 10x120mm Rawl frame fixings that I already have, as they will poke out the back of the Thermalite into the cavity, causing thermal and moisture bridging, and probably exploding the back of the block. I like the look of Fischer SRS Frame Fixings 10x100mm 50 pack £11.56 from Toolstation, for a cost/quality balance, that should give me 75-80mm into the block.
http://www.toolstation.com/shop/Scr...SRS+Frame+Fixing+10+x+100mm/d90/sd1950/p82988
I think cheap unbranded is OK for fence posts, if one breaks you can just drill another hole next to it and no one will notice, but for a kitchen unit you can't just put the bracket in a different place, so worth a few extra pence for less agro IMHO. There are a few negative reviews on Screwfix for the expanding Sleeve Anchor type as you can strip the plastic thread in the cork/plug, so I figured stick with the more conventional nylon plug.
As the dry lining isn't up yet, I will try to be generous on the adhesive, putting a continuous bead along the line of the top of the kitchen units, that way I can keep air gaps to a minimum, poorer thermal insulation, but stronger.
I took my testing a stage further, and you can see my rig test, made from 1off 100mm Thermalite block, 2off 25x30cm shelf brackets, and some bathroom scales. I tested different fasteners that I happened to have to hold the shelf bracket to the block, 1 at a time, pushing on the bathroom scales and making a note of the maximum force they could withstand. I tested 7 different fastening arrangements, 3 times each and came up with the following results. Obviously if I had made to effort to dob and dab some plasterboard onto the front of the block it would have been a better test. My Green Bosch 24v only has 5 Torque setting, and Torque = Drill setting.Wood Screw, Plug (mm), Torque, Kg
4x30mm, No Plug, 1, 15kg
5x40mm, No Plug, 1, 20kg
4x30mm, Yellow, 25mm, 1, 25kg
4x35mm, Red, 30mm, 1, 40kg
5x40mm, Brown, 35mm, 2, 70kg
5x100mm, No Plug, 2, 70kg
5x40mm, 14x33 Self Screw, 3, 70kg
(can you do table on here?)
At 70kg the shelf brackets started to bend, and I am only 77kgs so it was not possible to test beyond this. Also with 4 fixing per kitchen wall unit, 70kg x4 = 280kg, so not really necessary to test beyond this other than out of curiousity. Interestingly on a best of 3 the Self Screw aluminium plasterboard plug failed first at 10 then 20 and finally 70kg, so results not consistent. It shows that the correct size of pilot hole and torque used is very important, any cracks and it is severely compromised. I didn't test the 7x120mm screw with the 10x120mm Rawl Plug, frame fixing, because it would clearly hold more than 70kg.
Conclusion.
I don't want to use the 10x120mm Rawl frame fixings that I already have, as they will poke out the back of the Thermalite into the cavity, causing thermal and moisture bridging, and probably exploding the back of the block. I like the look of Fischer SRS Frame Fixings 10x100mm 50 pack £11.56 from Toolstation, for a cost/quality balance, that should give me 75-80mm into the block.
http://www.toolstation.com/shop/Scr...SRS+Frame+Fixing+10+x+100mm/d90/sd1950/p82988
I think cheap unbranded is OK for fence posts, if one breaks you can just drill another hole next to it and no one will notice, but for a kitchen unit you can't just put the bracket in a different place, so worth a few extra pence for less agro IMHO. There are a few negative reviews on Screwfix for the expanding Sleeve Anchor type as you can strip the plastic thread in the cork/plug, so I figured stick with the more conventional nylon plug.
As the dry lining isn't up yet, I will try to be generous on the adhesive, putting a continuous bead along the line of the top of the kitchen units, that way I can keep air gaps to a minimum, poorer thermal insulation, but stronger.
Clad the wall with sheet osb then you need no fixings as you can screw everything to the timber thru the plasterboard.
That sounds like a good idea, although obviously more work/cost, would you clad the whole wall or just the parts where you intended to hang wall units, extractor hood etc? Also the electric and gas services have to go in next, so you would have to chase it out for the gas pipe, and it would increase the flammability if a cable should (which it shouldn't) overheat. Also what would you then fix the 18mm OSB to the Thermalite with, presumably lots of 40mm brown nylon plugs, with 5x60mm wood screws?
Install pipes first and cut out for them?
Only needs 11mm osb, screwed to wall.
Clad entire wall then if you change layout you can be sure there is timber behind.
You entire kitchen will be flammable , not a consideration.
You could insulate the wall while it's open.
Only needs 11mm osb, screwed to wall.
Clad entire wall then if you change layout you can be sure there is timber behind.
You entire kitchen will be flammable , not a consideration.
You could insulate the wall while it's open.
Thanks Foxhole. I don't think I will insulate, as the brick/thermalite cavity is insulated with 50mm of Celotex, and I'd rather not make the kitchen smaller. I have already over specked on roof insulation figuring that heat rises so that was the most important, with 150mm of Celotex rather than the 120mm's specified by building control.
DIYnot Local
Staff member
If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.
Select the supplier or trade you require, enter your location to begin your search.
Are you a trade or supplier? You can create your listing free at DIYnot Local
Sponsored Links
