Workshop floors, sloped or horizontal, guidance request.

[Martyn PooleParticipant @martynpoole48399]

Having been greatly distracted by some unfortunate family problems since I joined the Forum, my (Model) Engineering has not progressed very well, hence my silence. All I seem to get the spare time to do is to try and sort out my workshops and enjoy being a silent observer on this wonderfully informative Forum.

My workshops are in what was a set of old brick built lock up garages that I own, and I am converting three into separate workshops, one dedicated to metal machining (a turnery), a general clean workshop for planning, painting and electrical projects etc., and a woodworking shop. Luckily I have a separate free standing shed for dirty metal work, like grinding and welding.

The garage floors have a slopes varying between about 1 and 5 degrees, from the rear wall to the front double doors, which I guess was done to allow drainage from vehicles within as the site is not prone to flooding. Not only are the slopes irregularly executed but the concrete floors are in poor condition so they must be refurbished, and I wonder if I should, as part of this work, level the floors in all directions to give a horizontal surfaces.

Having given it much thought I cannot make up my mind if the advantages of having a flat horizontal surface to work off is better than having a plane surface with a gentle slope to assist dealing with spillages or water ingress.

What do you think I should do?

[Thor 🇳🇴Participant @thor]

Hi Martyn,

Might depend on what you intend to do in your workshops and if you move your machines around. My workshop has horizontal floor, this makes it easy to move equipment, I have casters under most of my equipment and adjustable feet that I lower when the machine is in the right place.

Thor

[Nigel Graham 2Participant @nigelgraham2]

I’d level the floor.

Yes, spills can occur but are not ever so likely or frequent, and the ability to move machines on castors, or even just trolleys, safely is a big advantage outweighing the occasional extra housekeeping.

[John HaineParticipant @johnhaine32865]

When you want to “level” a lathe, using a precision level to get any twist out of the bed, having a non-level floor would be a b****r!

[John Haine]

On John Haine Said:

When you want to “level” a lathe, using a precision level to get any twist out of the bed, having a non-level floor would be a b****r!

Would make very little difference, just fit packers under the cabinet to get it something like level, then set to on the lathe itself

[Grindstone CowboyParticipant @grindstonecowboy]

I agree with Duncan, it won’t matter for ‘levelling’ the lathe. A slight slope, say 1 degree max (about 20mm per metre), would probably be an advantage just in case of unintended liquid spillage or ingress and is unlikely to cause problems when shifting heavy things.

Rob

[Robert Atkinson 2Participant @robertatkinson2]

Easiest way to get a smooth surface would be to use a modern self-levelling compound. This will by definition be level.
My vote would be for level in any case.

Robert.

[ChrisLHParticipant @chrislh]

My workshop floor is as level as makes no diffrence for everything I do. Were I to be in the OP’s position I would wonder how uncomfortable standing for long periods (e.g. at the lathe) on a sloping floor would be. I don’t suppose there are any rules so the best way to find out would be to try it with your floor and your body.

[duncan webster 1Participant @duncanwebster1]

As the original buildings were garages there is unlikely to be a DPC under the floor. Had my floor levelled with mastic asphalt which gives a pretty smooth watertight surface. Then I put 25mm foam and flooring grade chipboard on top. Where the heavy machines are cut holes for blocks to take the load back to the asphalt.

[Martyn Poole]

On 13 March 2024 at 18:44 Martyn Poole Said:

…

The garage floors have a slopes varying between about 1 and 5 degrees, from the rear wall to the front double doors, which I guess was done to allow drainage from vehicles within as the site is not prone to flooding….

Are you serious? A five degree slope is an 18-inch fall over the length of a single car garage. That’s not a floor. That’s a ramp.

Wear one 4″ stiletto heeled shoe and one flip flop and you might be able to work on it.

[BazyleParticipant @bazyle]

If the garages can now or by a future owner be used as a garage ie for the storage of a car, then there is I believe a legal requirement to have a sloping floor. If you brick up the main door to prevent that you might still need planning consent for change of use.

[Bazyle]

On Bazyle Said:

If the garages can now or by a future owner be used as a garage ie for the storage of a car, then there is I believe a legal requirement to have a sloping floor. If you brick up the main door to prevent that you might still need planning consent for change of use.

Yes usually an inch or two of fall to facilitate run-off. But 18 inches????

[JasonBModerator @jasonb]

And by the time you have added 450mm to level the floor, thats assuming you don’t need to do anything to the high point which if in poor condition may need building up you will be faced with other problems.

Average 7ft garage door will now be 5’6″ so mind your head driving that tractor in! The resulting low ceiling height will then affect height of things like mills that will fit in and allow the drawbar to be changed. Woodwork shop won’t allow easy manovering of 8×4 sheets, etc

You will also then need steps or a ramp to get up from ground level to the workshop. How will you get machines etc in from the lower external areas.

[Robert Atkinson 2Participant @robertatkinson2]

The sloping floor requirement is only for integral garages. As an alternative you can hav3 a 100mm step down to the garage from the house. It does not sound like the OP’s garages are integral. See B3 5.3 (page 30) of
https://assets.publishing.service.gov.uk/government/uploads/system/uploads/attachment_data/file/485420/BR_PDF_AD_B1_2013.pdf

This is as you can see a fire precaution so any fuel will drain outside. Interesting to see what they will do about EV’s where the energy source won’t drain away. Probably enhanced fire reistant linings.

Robert.

[JasonBModerator @jasonb]

The step down has been the norm for years, the slope was introduced more for wheelchair access than draining leaks. Not much point in having part M compliant thresholds on the doors if someone wants to drive into a garage and get into their chair and then has to go outside to get back into the house, or simply wants to go to and from the house and integral garage.

[Martyn PooleParticipant @martynpoole48399]

Thanks for all the helpful comments so far, much food for thought. However, I feel some clarification is in order.

The slope in any one garage may well be 5 degrees at some point as it seems to follow the roof pitch, but it is not consistent in any of them. All I can say with certainty is the floors are not level. My rough assessment was not helped by the fact we were using the Apple iPhone measure app which went haywire during the course of the investigation.

Headroom may not be an issue as once I have decided on the floor plane orientation I can either go up, that is lay a new floor on the existing or go down and dig out the defective concrete as there is no dpc.

The garages are also built on a lateral slope and while the exterior roof is level each one has a different internal roof height. By the time I get to the last one, the intended metal shop, it is entirely adequate for my purposes. I also do not intend to bring any vehicles. e.g. my tractors (I have more than the small one pictured) inside as I have a separate garage as well.

[JAParticipant @ja]

If there is something large and sits close to the floor, like a lathe on a cabinet, at the bottom of the slope the workshop elves will love you. They will tax you for all you are worth. Any small item dropped on the floor will be lost.

JA

By the way, they do exist.

[OldironParticipant @oldiron]

40 odd years ago I bought a block of buildings from the local council comprising of 6 garages on the ground floor with 2 x 2 bed flats above and 2 stair wells. I converted the whole block into one house over 3 years. I now have 5 bedrooms, study & library etc etc. I keep 2 garages as were. One of the other garages was converted into a small workshop and a wet shower/toilet room.

I left the workshop floor sloped as it was so little and could hardly be noticed when walking on it. By the time the benches were in and the machines leveled up on their legs the slope was not really noticeable. Never given it a thought until today.

All the other converted rooms had to have a dpc liner and insulation before the concrete floors were poured. The only planning permission needed was to add extra windows and move an external door + change of use for the new living areas. No change of use was needed for the workshop area. Even bricking in the old garage door openings did not need planning permission but was covered by building consent which is a different kettle of fish. It means that the alteration needs to conform to building regulations.

[Martyn Poole]

On Martyn Poole Said:

Thanks for all the helpful comments so far, much food for thought. However, I feel some clarification is in order.

The slope in any one garage may well be 5 degrees at some point as it seems to follow the roof pitch, but it is not consistent in any of them. All I can say with certainty is the floors are not level. My rough assessment was not helped by the fact we were using the Apple iPhone measure app which went haywire during the course of the investigation.

I think, then, that before you can get meaningful answers to your question, you need some meaningful measurements of just how much slope is really involved. Might be as simple as a string line with a clip-on spirit level bubble held level across the length of the garage floor and measure how many inches or mm of drop at the low end overall.

At the moment your only certainty, you say, is that the floors are “not level”. which can mean anything from two thou to two feet out in the current context.

[JasonB]

On JasonB Said:

The step down has been the norm for years, the slope was introduced more for wheelchair access than draining leaks. Not much point in having part M compliant thresholds on the doors if someone wants to drive into a garage and get into their chair and then has to go outside to get back into the house, or simply wants to go to and from the house and integral garage.

The wheelchair access may be in current regulations; I don’t know.  However, my father’s 1930s integral garage had a sloping floor, and he told me it was to allow rainwater, melted snow or leaked fuel to drain outdoors. It would not have been possible to get a wheelchair alongside the car.  The garage ceiling as built was a single layer of Celotex board nailed to the joists of my bedroom above!  Dad wouldn’t park the car indoors until he had a proper fire resistant ceiling (30 minute) installed.

My 1970s separate garage has a sloping concrete floor too, and the concrete is as rough as something proverbial.  I built a flooring frame of 3″ x 2″, set it on a waterproof membrane and levelled it, added flooring grade chipboard and finished with cheap B&Q laminate.  It’s dry and comfortable to stand on.  The only drawback is that when I drop anything substantial it makes a ‘ding’ in the rather brittle laminate.

George

[Robert Atkinson 2Participant @robertatkinson2]

Jason B, Do you have a reference for the wheelchair access? I can’t find any reference in the guidance
https://assets.publishing.service.gov.uk/media/5a7f8a82ed915d74e622b17b/BR_PDF_AD_M1_2015_with_2016_amendments_V3.pdf
It seems very strange especially as most UK garages are not wheelchair accessible with a car in.
I even revisited the fire guidance and noted that the slope is only required if the garage is attached (or integral) AND has a door between house and garage. So this is presumably to stop spilt fuel and maybe vapour, running into the house.

Robert.

[Martyn PooleParticipant @martynpoole48399]

In retrospect I realise I did not make myself clear as I was really only looking for a qualitative answer to my question “to slope or not to slope” rather than any detailed quantitative proposals however I am very grateful for the in-depth observations offered. In respect of the query about the gradient I am trying to deal with now, the answer is that the garages are 5.6 metres long internally and the difference in floor level front to back is about 75mm.

Anyway at this point I think I am going to go with the “Levellers” amongst you (nothing to do with  the 17th Century political movement or the 1980s pop band from Brighton) as I am drawn to the idea of moving machines on castors about easily and I don’t think I have the skills and resources available to lay a floor accurately with a very small incline to facilitate this and assist with the remote possibility of dealing more easily with a major spillage, flood or gas leak. To address those issues I will probably fit floor level vents and drain holes.

Once again thanks for all the helpful comments and advice and I will report back how I get on when the floors are laid although regrettably that is very likely to be very many months in the future.

[JasonBModerator @jasonb]

Robert, see 2.21 which says doors to a garage or carport should comply to various items in 2.20 of which h is wheelchair accessible threshold which you can’t really have if there is a 150mm step.

Yes it would need to be a double garage or if a house built specifically for someome in a wheelchair at least wider than a single garage. If the person in the chair is not driving then you could get away with a long single width if they are entering via the rear of a suitably modified mobility vehicle.

I always understood it wa sto prevent spills flowing under the door to the hous ebut as you say would also stop a heavier than air gas such as propane from a cylinder or LPG from a converted car

[Author]

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