How thick do exterior walls have to be?

Author: Freida Goldner  |  Last update: Wednesday, September 17, 2025

Standard ICF external walls need six inches of concrete. However, areas susceptible to high winds require concrete thickness of at least 8 inches. The engineering tables review several characteristics of the building's design and location when establishing the concrete core size and the rebar layout.

What is the minimum thickness of exterior walls?

The minimum thickness of exterior walls in one-story buildings shall be 10 inches (254 mm). The walls shall be laterally supported at intervals not exceeding 24 feet (7315 mm). The minimum thickness of interior load-bearing walls shall be 8 inches (203 mm).

How thick does an external wall have to be?

External wall thickness typically ranges between 50mm and 100mm to achieve a U-value of 0.3W/m2K, as required by UK building regulations.

Should exterior walls be 2x4 or 2X6?

Definitely 2x6, regardless of insulation plans. 2x6 walls are significantly heavier walls and offer more strength in cases of wind load.

How thick should exterior wall sheathing be?

9 and this section on all sheathable exterior wall surfaces, including areas above and below openings. Structural sheathing panels shall consist of minimum 7/16-inch-thick (11 mm) oriented strand board or 15/32-inch-thick (12 mm) plywood.

Thickness of Walls | Masonry

Is 7/16 OSB good for exterior walls?

Wall Impact Resistance - Ensure that all exterior walls are constructed using a wall system that provides, at a minimum, the resistance to wind pressures and debris impact provided by 7/16-in. -thick OSB wood structural panels attached to wood wall framing.

What is the proper framing for exterior walls?

How to Frame Exterior Walls
  1. Exterior walls are usually constructed as a single piece and framed with 2- x 4-inch or 2- x 6-inch boards, then raised into place. ...
  2. Measure the dimensions of the wall. ...
  3. Lay out the wall's top plates and bottom plates.
  4. Measure and mark for the studs at 16-inch intervals.

Are 2x6 exterior walls code?

2 x 4 framing is generally code compliant. Here at Medeek Design we typically only specify 2 x 4 studs @ 16" o.c. spacing, for small sheds and garages with a building widths less than 16 feet. All other larger structures are generally called out with 2 x 6 exterior studs @ 16" o.c. unless specified otherwise.

Can a 2x4 wall support a second story?

Existing 2 x 4 walls do not preclude a second floor, but they must be looked at carefully (visually and by calculation) to assure that they will accept additional load.

How can you determine the thickness of the exterior wall?

The exterior wall thickness can be determined by measuring the thickness of the exterior door casings and/or exterior window casings. In this case it will be a window casing. The main living area is measured using the width and length and adding the wall thickness to both ends of the dimensions.

How far out of plumb can a wall be?

The Residential Construction Performance Guidelines suggest a maximum out of plumb of 3/8″ in 32″ vertically, while the Handbook of Construction Tolerances suggests that this may need to be tightened to 1/4″ in 10ˈ when finishes such as gypsum wallboard and plaster are used.

What kind of walls are in old houses?

If you have an old house, it's likely your walls are either plaster or some kind of original wood paneling. This may be hidden under layers of unfortunate redecorating attempts, but it's probably there. If you have plaster, you're at the bottom layer and shouldn't rip into it further.

How thick is a modern external wall?

A solid brick wall is usually about 22 cm thick, a cavity wall between 27 cm and 30 cm thick, and a solid stone wall could be as much as 50 cm. The age of your home can also be a good indicator. As a general rule, if it was built before the late 1920s it is unlikely to have a cavity.

How thick are garage walls?

Determining the ideal thickness of plywood for garage walls involves balancing durability, load-bearing capacity, and cost-effectiveness. In general, for most garage wall applications, plywood between 1/2 inch and 5/8 inch thick is considered adequate.

Are 2x4 exterior walls OK?

Modern conventional home building normally makes use of 2x4 lumber (top line above, second from left) in constructing exterior walls. But 2x6 framing, which is a little more than 1.5 times wider, is a common upgrade and is required by some local building codes.

What is required on the top of all exterior walls?

1403.2 Water-resistive barrier.

The water-resistive barrier material shall be continuous to the top of walls and terminated at penetrations and building appendages in a manner to meet the requirements of the exterior wall envelope as described in Section 1402.2.

What size lumber is used for exterior walls?

Wood-framed houses have traditionally been built with 2x4 studs spaced 16-inches on-center. Research has shown exterior framed walls can be adequately supported by 2x6 studs spaced 24-inches on-center.

What is the cheapest way to build an exterior wall?

What Is the Cheapest Material to Build a Wall With? While prices of materials will vary depending on where you're building, the least expensive types of siding for exterior walls tend to be vinyl and composite. Vinyl is synthetic, low-maintenance, and comes in all different types to match aesthetic desires.

What kind of sheathing for exterior walls?

Modern sheathing options include oriented strand board (OSB), plywood, foam board, gypsum, and structural fiberboard. These materials provide better moisture resistance, structural integrity, and energy efficiency compared to older options like plank and Celotex sheathing.

What is the best wood for exterior framing?

Douglas Fir

This wood is great for exterior work; it doesn't warp or twist as some other woods do. Douglas fir lumber is graded #2 (good) and #3 (common). Exterior grades are knot-free with good face values; it's also graded under the National Hardwood Lumber Association grading rules.

Should I use plywood or OSB for exterior walls?

That, in a nutshell, is the one big advantage plywood holds over OSB. The greater ability a wall has to dry, the more durable it will be, and everyone agrees that more moisture will pass through plywood.

How long will an OSB board last outside?

The service life of OSB is indefinite (expect 50 years or longer) if it is used and protected properly. 2. OSB should not be used where it is permanently exposed to the outdoor environment unless panels are qualified as Exterior (e.g. siding) and recommended coating is periodically renewed.

Which is stronger, 3/4 plywood or 3/4 OSB?

Strength. OSB and plywood are very similar in terms of strength, but plywood is stiffer than OSB by a factor of approximately 10%.

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