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Garage, shop, shed and RV pads matched to their real loads
A plain slab looks like the simplest concrete there is, but it is where the wrong assumptions cost the most. A shed pad poured for garden tools ends up holding a workbench, a compressor and a motorcycle. An RV pad built like a patio cracks under the first motorhome. A garage floor poured without thought for anchors, drainage or moisture turns into a problem once walls go up. In El Paso, where campers, trailers and workshops are part of many households, this page explains how to size a slab for its actual job and how to read a quote for one.
Tell the contractor what the slab is really for
The load decides almost everything. A tool shed, a two-bay detached garage, a pickup carport and a motorhome pad are four very different slabs, even if they share the same footprint. The weight, how it is spread and whether it moves all matter. A parked camper puts heavy, steady loads on a few tires and jacks. A car in a garage drives on and off every day. A workshop may have machinery that vibrates or bolts down.
Say what will sit there today and what might sit there later. It costs far less to thicken a slab during the pour than to replace it after a heavier trailer arrives. Include the plan for walls, a roof or a door, because those change the edges and the anchors.
Thickness, edges and reinforcement
Lightly loaded pads, like a garden shed floor or a patio, are often placed about four inches deep. Garage floors, carports and pads that carry trucks or trailers are commonly thicker, and RV pads often more so. Edges carry concentrated loads from walls and from tires rolling on and off, so slabs for buildings usually have thickened edges or a separate perimeter footing, depending on the design.
Reinforcement holds the slab together once it cracks, and every slab cracks somewhere. Welded wire, rebar in a grid, and fibers in the mix are all common, sometimes in combination. What matters most is that steel ends up within the slab rather than lying on the base. For heavy pads, ask what size and spacing of reinforcement is planned and how it will be supported.
Base preparation on desert soils
A slab is only as good as the ground below. El Paso soils vary from loose sand to hard caliche to clay near the river, and many lots also have areas of fill from when the subdivision was graded. Loose, dry soils may compress when they get wet for the first time, and that settlement can be sudden. A careful job removes organic and loose material, moistens and compacts the native soil, and places a compacted base of crushed rock or road base on top.
For a heavy RV or trailer pad, base thickness and compaction deserve extra attention. Get the dig depth, the type of rock or road base and the compaction method in writing. A slab poured over a base that was spread but not compacted may look fine for a year and then start to sink along the wheel tracks.
Garages, workshops and enclosed buildings
When walls will stand on a slab, the details get more specific. Anchor bolts or straps usually need to be set in the fresh concrete at the right spots for the walls, so the building layout has to be known before the pour. The slab has to be square and level where the walls sit, and the floor inside is often sloped slightly toward the door so water can drain out.
A vapor barrier under the slab is commonly used for enclosed spaces where moisture coming up through the floor would cause trouble, such as a workshop, storage for cardboard boxes or a finished room. In a dry climate, soil moisture is often low, but irrigation, a nearby pool or monsoon runoff can raise it. Ask whether a barrier is planned.
Buildings on slabs often need a permit and plan review, and larger or habitable structures may need an engineered foundation. Check with the city or county and your HOA before ordering a kit or scheduling the concrete, because the approved plans may set the slab details.
RV and trailer pads in the side yard
Many El Paso homes store a camper, a boat or a work trailer beside the house. The pad has to be long and wide enough for the unit plus room to open doors and slide-outs, and the approach has to allow backing in without driving over rock landscaping or clipping a wall. Measure the unit and the gate opening, and think about how you will actually maneuver it in.
A side-yard pad usually needs a solid transition to the driveway and a slope that carries water away from the house and toward the street or a gravel area. Where it passes a block wall or a neighbor's fence, the base should be kept from undermining the wall footing. Check with your HOA and the city or county about any limits on parking or storing vehicles beside the house.
Access for trucks and pumps
Back yards in El Paso are often enclosed by rock or block walls with narrow gates. A concrete truck cannot always get close, and an older wall may not take the weight of a truck next to it. When direct access is not possible, the concrete may be moved with a line pump, a boom pump or buggies. Each has its own cost and scheduling, so ask the contractor how the concrete will reach the pad.
Ask also about the route for removing dirt and old material, and about protecting the driveway, curbs and landscaping along the way.
Checklist for a slab quote
- Dimensions, thickness and any thickened edges or footings.
- Excavation, base material and base depth, and compaction method.
- Reinforcement type, size and support.
- Anchor bolts or straps, vapor barrier and interior slope if walls will be built.
- Joint layout and spacing, which is commonly two to three times the slab thickness in feet.
- Finish and surface level where walls or equipment will sit.
- Access method, including pump or buggy if needed, and haul-off of spoils.
- Who handles any required approval, and whether an engineered plan is needed.
Garage, shop, shed and RV pads matched to their real loads — common questions
How thick should a shed slab be?
For a small shed holding garden tools on well-prepared ground, a slab around four inches thick is common. If the shed will hold heavy equipment, a riding mower, a workbench with machinery or a motorcycle, the slab may need to be thicker or more heavily reinforced. Larger sheds may need thickened edges for the walls. Tell the contractor what will be stored inside and ask for the planned thickness in writing.
Is gravel good enough for an RV pad?
Gravel can work for parking, and some homeowners use it for that, but it tends to rut, shift and spread over time, and weeds can grow through. A concrete pad gives a flat, stable surface for leveling jacks, is easier to keep clean, and looks tidier from the street. If you choose concrete, make sure the thickness and base are sized for the weight of the unit, not for a patio. Check HOA rules on RV parking first.
Do I need a vapor barrier under a garage slab?
It depends on how the space is used. For a garage that stays open and dry, a barrier is sometimes skipped. For a workshop, a storage room or any space where flooring or boxes sit on the slab, a vapor barrier is a common choice to limit moisture coming up through the concrete. Irrigation, pools and monsoon runoff nearby can raise soil moisture even in a dry climate. Ask the contractor what they recommend.
Why do anchor bolts need to be placed before the pour?
Bolts and straps cast into fresh concrete hold walls to the slab far more securely than anchors drilled in later, and they sit exactly where the wall plates will go. Setting them requires knowing the building layout, the wall locations and the door openings before the concrete arrives. If you are building a garage, workshop or shed kit, share the plans with the contractor ahead of time so anchors can be set correctly.
Can a slab be poured behind a block wall with a narrow gate?
Usually, yes, but the method changes. If a truck cannot reach, the concrete may be moved by a line pump, a boom pump or motorized buggies through the gate. A contractor will look at gate width, the distance to the pad, overhead lines and whether the wall could be damaged by a truck parked close. The access method affects scheduling and cost, so it should be described clearly in the quote.
Does a detached garage slab need a permit?
Many cities and counties require approval for new buildings, and a detached garage usually counts. The approved plans may also set requirements for the slab and footings. The rules differ between the City of El Paso, surrounding municipalities, El Paso County and any HOA, so check with each one that applies to your property before scheduling the concrete. The contractor can often tell you which office to contact.
Talk through your project
Start with the address, what you want poured or replaced, rough dimensions, and a few photos of the area and any existing concrete.
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