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New workshop building advice.

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Brian Abbott06/04/2018 22:02:40
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319 forum posts
51 photos

Hello all, I am after some advice, not ME related but building so please excuse me.

I am looking at replacing an old shed I have with a timber framed workshop which will lean up against my existing garage.
I would like a concrete floor with a DPM which will stand about 6” above the existing garden slabs ( this will bring it level with my existing garage floor if I ever decide to knock through)
I would also like the concrete slab to be brick faced and build the timber frame of this.

Problem I have is my next door neighbours garden is about 12” lower than mine to I was planning to put a concrete footing in, my question is looking at the drawing do you think this arrangement will work with a single skin of brick work, will I be ok to hardcore and concrete against a single skin.

I do plan to try and get a builder to do the ground work but wanted to do some homework first.

Any advice, thank you

Brian Abbott06/04/2018 22:03:09
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319 forum posts
51 photos

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richardandtracy06/04/2018 22:25:45
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854 forum posts
10 photos

In 2010 my family & I demolished a building where the foundation had failed and replaced it.

The foundation of the original building was a scrape in the Victorian soil surface and lime mortar spludged on it. The building was on a map dating to 1890, and the foundation failed in 2008. The walls were 6'6" high, 9" brick. The thing weighed tons and was sitting on a strip of mortar on top soil.

How long will the building need to last, and do you think you are going to need to sell it? If you may need to sell, then double skin construction, especially covering the bricks will be needed. But if you never anticipate moving, do what you like, you won't care in the future and all sorts of stuff lasts a heck of a time. My parent's last house was mud and rubble, the roof timbers still had the bark on in places. The floor under the stairs was river stone cobbles hammered into the mud. And it was 400 years old.

Regards

Richard.

Bazyle06/04/2018 22:44:09
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3910 forum posts
166 photos

Check your planning regulations You are possibly only allowed 8ft high wrt the ground level and may not be allowed a timber building on the property line unless the original structure had planning permission. Worth making the wall plinth self supporting so that you can extend the under floor insulation up to meet the wall insulation to avoid a cold bridge.

David George 106/04/2018 23:03:35
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370 forum posts
129 photos

Hi Brian I extended the rear of our property for an extension. I had to get permission from the owner of the adjoining house next door under the party wall act as it was over 8 ft tall and could block light etc but no problem with permission. I would think there could be a problem with noise if the wall was wood and if the workshop was near to a dwelling ? Also the thickness of the floor should be thicker and have steel reinforcing. Have you considered insulation under the floor?

David

Clive Foster06/04/2018 23:33:29
1317 forum posts
29 photos

Brian

What you are proposing with the single skin brickwork isn't vastly dissimilar to the low side of my timber frame workshop which is about a foot above ground level. Need daylight to check but as I recall matters there are only two courses of brick above the slab with the DPM between as in your diagram.

However I have serious concrete under my floor. Bricks were laid all round first on normal foundations as required then back filled with concrete. About a foot with mesh re-enforcement, then a polystyrene insulation layer with 6" more concrete on top and, finally, the waterproof, green finished, chipboard under-flooring sheets used as is for the floor surface.

Noise shouldn't be an issue. I have 4 x 2 framing with OSB both sides. Fibreglass insulation between the OSB and painted shiplap outside. Proper house type double glazed windows. Anything short of an angle grinder or similarly seriously loud equipment is essentially inaudible outside.

Clive.

J Hancock07/04/2018 07:39:06
225 forum posts

Think what will happen when the wind and rain conspire to blow directly under that gutter ?

I would try to slope the roof, as much as you can, away from the garage/workshop interface.

Flat/flat roof and sealing against wall ,can be a problem.

Howard Lewis07/04/2018 12:10:15
1161 forum posts

+1 for adequate slope on the roof to ensure drainage, 1:80 works on mine., but wouldn't want to be much flatter.

Ensure that joints are sealed, to prevent ingress of wind, rain, snow, dust etc. Downpipes on gutters should prevent damp getting in through the walls. Just ensure that the water can then get away from the shoe, when it reached ground level..

Having said that, do ensure ventilation, with weatherproof grilles at floor level (to allow damp /moisture out) and at high level for replacement air.

If you are planning to store metal in there, beware of rust/corrosion. So insulate walls and ceiling (50mm glass fibre is my choice)

You cannot have too many power points (as long as you do not overload the feed circuit). Ideal feed is via RCD consumer unit with separate circuits for lighting and power. If you have no windows, (for security) you will need an automatic emergency light against the time of any mains failure.

With windows, ideally they need to be vandal/thief proof, so with grilles or unbreakable material such as Makrolon, or Georgian Wired Glass. Double glaze, if you like!

The door(s) should have a 5 lever lock, and hinge bolts. My wooden shop has hinge bolts made from woodscrews with the heads turned off and screwed into the back of the door, and entering into clearance holes in the door frame. In that way, the lock is difficult to pick, even if the hinge pins are driven out, the door cannot be lifted out.

Fit an Intruder Alarm as well, if you wish.

(I have a simple wired Intercom, so that I can be called for meals/visitors. A mains baby alarm in the hall alerts me to the front door bell being rung).

Sad that we have to go to such lengths, but you have to safeguard valuable contents against vandals and thieves.

Heating should be electric, not gas, liquid, or solid fuel. All the latter emit water vapour which will aid rust, and in an enclosed space, lethal fumes. Even with an external flue, adequate air for combustion is absolutely necessary, and leaks can prove fatal. As humans, we emit water vapour as we breathe.

A well insulated shop will need less heating, (My fan heater runs through a thermostat. Once up to temperature, it spends little time running)

Don't forget a powder fire extinguisher.

Hope that all this rambling is of some help

Howard

Hillclimber07/04/2018 12:16:41
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113 forum posts
24 photos

One suggestion - I have never heard anyone say they had over-insulated their workshop.

Samsaranda07/04/2018 12:33:10
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384 forum posts
4 photos

My wooden outer walls stand on 9 inch concrete blocks, this keeps them away from ground moisture and a lot easier to construct than brick courses, and cheaper. Agree with comment you cannot over insulate, my walls are 100 mm of Celotex and same with roof, no rusting problems as temperature remains fairly constant, have also installed a dehumidifier that runs during the night, uses economy 7 electric and is permanently plumbed in. Need to check building regs re proximity to property boundary.

Dave W

Clive Foster07/04/2018 13:09:41
1317 forum posts
29 photos

Concerning the proposed roof layout consider integrating your workshop roof into the main garage roof giving a continuous fall. Probably need to put a slight bend in the fall and loose a bit of height at the far wall. Less than ideal but should you have roof problems in the under gutter region they will be a major, expensive, PIA to fix post build.

Its also possible to put a gutter or similar drainage between two roof sections.

Best to talk to good builder with relevant experience.

Clive

Ian S C07/04/2018 13:43:40
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6776 forum posts
224 photos

A normal building in NZ has a wooden frame(treated pine), the weather proof outer skin can be brick, timber, or others such as foam plastic with a roughcast coating. But the bricks are non structural, and refered as a veneer. A building that close to a boundary would require to be a fire retardant type, not being a builder, and not having a building of that type I'm not sure what is involved The roof would require a minimum pitch of 8* for a corigated iron roof.

Ian S C

Neil A07/04/2018 20:58:00
20 forum posts

If you are looking for ideas on building a new workshop, I can recommend buying a copy of "Workshop Construction" number 23 in the workshop Practice Series. It gives a great deal of information on various methods of construction and some advice on planning regulations, although these may vary from district to district. I am sure you will find something in the book which will be of interest.

Neil

Brian Abbott07/04/2018 22:23:21
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319 forum posts
51 photos

Thanks Guys for all the advice, i am trying to find a 'good' builder, or any builder for that matter to take a look but none seem interested, anyway, thanks agian.

Brian Abbott18/05/2018 09:03:50
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319 forum posts
51 photos

Hello all.

Not model related so I apologies but need to pick your brains.

Found a builder and started on the workshop extension and all going ok.

Talking to him last night about pouring the concrete base and the position of the DPM.

I asked if the DPM would lap up against the old garage wall, he said no as this becomes an internal wall and you should not do that,

He is the expert so I have to take his advice but it sounds wrong, anyone with any experience?

Thanks.

richardandtracy18/05/2018 10:00:22
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854 forum posts
10 photos

I have a Victorian house, no physical DPC, just a chemical one. So when we had a conservatory built, I insisted the dpc went up the wall to 4ft up. It was just as well, as the chemical DPC failed in a big way shortly after and the brand new conservatory plasterboard against the house wall would have needed re-skimming if I hadn't insisted.

It costs almost nothing, and won't be a problem to the builder if they are using studding for the internal finish. If they wanted to use dot & dab to stick plasterboard on, the dpc up the wall makes it impossible. That may be why he's resisting.

Regards,

Richard.

pgk pgk18/05/2018 10:18:02
1034 forum posts
278 photos

Yearss ago I built a DIY dwarf wall conservatory butting to a bay doorway using 2 Wicks 'victorian' kits back to back (so it was octagonal) and also lapped the DPC up the wall as per the kit instructions.. but then it was a cavity wall. Perhaps without a cavity one might worry about damp tracking through the lap??

pgk

richardandtracy18/05/2018 10:40:23
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854 forum posts
10 photos

Sorry forgot to mention my Victorian house has solid 9" thick brick where the problem arose. But the effect would have been the same had it been on the cavity part of the house (the front was built with a cavity to make it look fashionable).

In a more modern house with a physical dpc it may be worth taking the dpc fractionally above original house wall dpc level - or up to floor level if it's higher than the house dpc.

Regards,

Richard

Bazyle18/05/2018 12:09:02
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3910 forum posts
166 photos

Hi Brian, It's nice to get progress reports like this. Photos even more fun.

You need to think about where the damp is going. Water under the new slab will be trying to get up and out. So if the DPC goes up the wall it will direct the water up the wall into the bricks. If it extends up the wall it will protect the plasterboard if there is some but will make the wall inside wet instead. The new DPC needs to join physically to the existing DPC for the wall.
Personally in case the DPC joint leaked I would ensure the bottom 6 inches of cladding (if any) is a separate ventilated space for vapour to escape instead of creeping up the inside of the cladding.

peak418/05/2018 12:24:06
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497 forum posts
36 photos

Brian, re the felt roof, it might be worth investigating rubber sheet roofing, I think made by Firestone.

Available cut to size via the internet.

I've not used it myself, but heard good reports, easy to lay, no seams to leak, and easy to tee into the existing wall.

Bill

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